I lead the Productive Coasts research program within the Climate Change Cluster (C3) in the UTS Faculty of Science. Our goal is to contribute to the science that will help address Australia's grand challenges of food security, biodiversity conservation and ecosystem health, as well as climate variability and change. The outcomes of current projects will advance understanding of the adaptation of algae to changes in our climate. This is an important consideration in developing effective strategies to ensure these primary producers form a resilient foundation of marine ecosystems into the future.
My lab has conducted research on algae and microbes for more than 15 years, forming effective partnerships with government and industry to translate scientific research into management practices that improve environmental outcomes. We are interested in the capacity of algal communities to deal with short and long-term environmental change – not only to cope with contemporary shifts in climate, but also to harness nature’s innovations and put them to effective use in bio-industries.
- Director and CEO, Sydney Institute of Marine Science (2020 -
- Member, Scientific and Technical Advisory Committee IMOS (2018 -
- Users representative, Marine National Facility Steering Committee (2018 -
- ARC College of Experts (2014 - 2017)
- Node leader, NSW Integrated Marine Observing System (IMOS; 2013 - 2016)
- IMOS Radiometry Task Team (2017 -
- Marine National Facility Chief Scientist
- Member Australasian Society for Phycology and Aquatic Botany
- Member Australian Marine Sciences Association
- Member International Society for the Study of Harmful Algae
- Member American Geophysical Union
Algae and the future of food
Can supervise: YES
- Assessing impacts of climate change on coastal primary productivity, fisheries and the marine foodweb
- Understanding dynamics of pelagic systems, and integrating spatially-explicit observations from satellites and gliders into coastal management strategies
- Quantifying plasticity of algal populations to environmental change using advanced cell sorting and imaging technologies
- Improving resilience of algae in natural and cultivated systems through understanding trait diversity, physiological tradeoffs and cellular energetics
- Materials and energy exchange between algae and bacteria
- Underlying ecological mechanisms of invasion of tropical algae into temperate systems
ORCID ID: 0000-0001-8750-3433
Researcher ID: E-8719-2013
- Coordinator and Lecturer in Introduction to Oceanography (91167)
- Current Lecturer in Marine Communities (91157)
- Current Lecturer in Microbial Ecology (91170)
- Past Lecturer in Management of Coasts, Oceans & Catchments (98711)
- Past Lecturer in Environmental Management (91122)
Messer, LF, Ostrowski, M, Doblin, MA, Petrou, K, Baird, ME, Ingleton, T, Bissett, A, Van de Kamp, J, Nelson, T, Paulsen, I, Bodrossy, L, Fuhrman, JA, Seymour, JR & Brown, M 2020, 'Microbial tropicalization driven by a strengthening western ocean boundary current', GLOBAL CHANGE BIOLOGY.View/Download from: Publisher's site
Ajani, PA, Lim, HC, Verma, A, Lassudrie, M, McBean, K, Doblin, MA & Murray, SA 2020, 'First report of the potentially toxic marine diatomPseudo-nitzschia simulans(Bacillariophyceae) from the East Australian Current', PHYCOLOGICAL RESEARCH, vol. 68, no. 3, pp. 254-259.View/Download from: Publisher's site
Hughes, DJ, Crosswell, JR, Doblin, MA, Oxborough, K, Ralph, PJ, Varkey, D & Suggett, DJ 2020, 'Dynamic variability of the phytoplankton electron requirement for carbon fixation in eastern Australian waters', Journal of Marine Systems, vol. 202.View/Download from: Publisher's site
© 2019 Elsevier B.V. Fast Repetition Rate fluorometry (FRRf) generates high-resolution measures of phytoplankton primary productivity as electron transport rates (ETRs). How ETRs scale to corresponding inorganic carbon (C) uptake rates (the so-called electron requirement for carbon fixation, Φe,C), inherently describes the extent and effectiveness with which absorbed light energy drives C-fixation. However, it remains unclear whether and how Φe,C follows predictable patterns for oceanographic datasets spanning physically dynamic, and complex, environmental gradients. We utilise a unique high-throughput approach, coupling ETRs and 14C-incubations to produce a semi-continuous dataset of Φe,C (n = 80), predominantly from surface waters, along the Australian coast (Brisbane to the Tasman Sea), including the East Australian Current (EAC). Environmental conditions along this transect could be generally grouped into cooler, more nutrient-rich waters dominated by larger size-fractionated Chl-a (>10 μm) versus warmer nutrient-poorer waters dominated by smaller size-fractionated Chl-a (<2 μm). Whilst Φe,C was higher for warmer water samples, environmental conditions alone explained <20% variance of Φe,C, and changes in predominant size-fraction(s) distributions of Chl-a (biomass) failed to explain variance of Φe,C. Instead, normalised Stern-Volmer non-photochemical quenching (NPQNSV = F0'/Fv') was a better predictor of Φe,C, explaining ~55% of observed variability. NPQNSV is a physiological descriptor that accounts for changes in both long-term driven acclimation in non-radiative decay, and quasi-instantaneous PSII downregulation, and thus may prove a useful predictor of Φe,C across physically-dynamic regimes, provided the slope describing their relationship is predictable. We also consider recent advances in fluorescence-based corrections to evaluate the potential role of baseline fluorescence (Fb) in contributing to overestimation of Φe,C and the correlation between Φe,C...
Hughes, DJ, Giannini, FC, Ciotti, AM, Doblin, MA, Ralph, PJ, Varkey, D, Verma, A & Suggett, DJ 2020, 'Taxonomic variability in the electron requirement for carbon fixation across marine phytoplankton.', Journal of phycology.View/Download from: Publisher's site
Fast Repetition Rate fluorometry (FRRf) has been increasingly used to measure marine primary productivity by oceanographers to understand how carbon (C) uptake patterns vary over space and time in the global oceans. As FRRf measures electron transport rates through photosystem II (ETRPSII ), a critical, but difficult-to-predict conversion factor termed the "electron requirement for carbon fixation" (Φe,C ) is needed to scale ETRPSII to C-fixation rates. Recent studies have generally focused on understanding environmental regulation of Φe,C , while taxonomic control has been explored by only a handful of laboratory studies encompassing a limited diversity of phytoplankton species. We therefore assessed Φe,C for a wide range of marine phytoplankton (n=17 strains) spanning multiple taxonomic and size-classes. Data mined from previous studies were further considered to determine whether Φe,C variability could be explained by taxonomy versus other phenotypic traits influencing growth and physiological performance (e.g., cell size). We found that Φe,C exhibited considerable variability (~4-10 mol e- · [mol C]-1 ), and was negatively correlated with growth rate (R2 = 0.7, p < 0.01). Diatoms exhibited a lower Φe,C compared to chlorophytes during steady-state, nutrient-replete growth. Inclusion of meta-analysis data did not find significant relationships between Φe,C and class, or growth rate, although confounding factors inherent to methodological inconsistencies between studies likely contributed to this. Knowledge of empirical relationships between Φe,C and growth rate coupled with recent improvements in quantifying phytoplankton growth rates in-situ, facilitate up-scaling of FRRf campaigns to routinely derive Φe,C needed to assess ocean C-cycling.
Murray, JS, Nishimura, T, Finch, SC, Rhodes, LL, Puddick, J, Harwood, DT, Larsson, ME, Doblin, MA, Leung, P, Yan, M, Rise, F, Wilkins, AL & Prinsep, MR 2020, 'The role of 44-methylgambierone in ciguatera fish poisoning: Acute toxicity, production by marine microalgae and its potential as a biomarker for Gambierdiscus spp.', HARMFUL ALGAE, vol. 97.View/Download from: Publisher's site
Kulk, G, Platt, T, Dingle, J, Jackson, T, Joensson, BF, Bouman, HA, Babin, M, Brewin, RJW, Doblin, M, Estrada, M, Figueiras, FG, Furuya, K, Gonzalez-Benitez, N, Gudfinnsson, HG, Gudmundsson, K, Huang, B, Isada, T, Kovac, Z, Lutz, VA, Maranon, E, Raman, M, Richardson, K, Rozema, PD, van de Poll, WH, Segura, V, Tilstone, GH, Uitz, J, van Dongen-Vogels, V, Yoshikawa, T & Sathyendranath, S 2020, 'Primary Production, an Index of Climate Change in the Ocean: Satellite-Based Estimates over Two Decades', REMOTE SENSING, vol. 12, no. 5.View/Download from: Publisher's site
Miller, AD, Coleman, MA, Clark, J, Cook, R, Naga, Z, Doblin, MA, Hoffmann, AA, Sherman, CDH & Bellgrove, A 2020, 'Local thermal adaptation and limited gene flow constrain future climate responses of a marine ecosystem engineer', EVOLUTIONARY APPLICATIONS, vol. 13, no. 5, pp. 918-934.View/Download from: Publisher's site
Soja-Woźniak, M, Laiolo, L, Baird, ME, Matear, R, Clementson, L, Schroeder, T, Doblin, MA & Suthers, IM 2020, 'Effect of phytoplankton community size structure on remote-sensing reflectance and chlorophyll a products', Journal of Marine Systems, vol. 211.View/Download from: Publisher's site
© 2020 Elsevier B.V. Remotely-sensed ocean colour is the main tool for estimating chlorophyll a (Chl-a) concentration and primary productivity on the global scale. In order to investigate the source of errors in remotely-sensed Chl-a concentration we obtained in situ bio-optical properties, in situ reflectances, satellite-derived reflectances and the Chl-a concentration satellite products of the Ocean and Land Colour Instrument (OLCI) Instrument on board Sentinel-3 A in waters off eastern Australia. The mesoscale eddies of these oligotrophic waters provide contrasting phytoplankton communities that allowed us to focus on the effect of phytoplankton size as a source of errors. In these waters, cold-core cyclonic eddies (CE) are dominated by large phytoplankton cells, while small cells dominate warm-core anticyclonic eddies (ACE). The chlorophyll-specific absorption and backscattering from contrasting sites show significant difference due to the differing package effect of phytoplankton size distributions. After normalising the absorption and backscattering spectra to Chl-a associated with just small phytoplankton, the spectra of optical properties become much more similar, showing that small-sized phytoplankton dominate IOPs even when large cells contain the greater fraction of Chl-a concentration of the phytoplankton community. Measured in situ reflectances agreed with reflectances calculated using a simple optical model based on measured IOPs. Furthermore, the in situ measured reflectances agreed well with the OLCI reflectance (mean normalised bias (MNB) of 7% for wavelengths <600 nm). However, a systematic underestimation of Chl-a concentrations by the OLCI algorithms was found in the region of cyclonic eddies characterised by increased Chl-a concentration and dominance of large-sized phytoplankton. A similar underprediction was found in Chl-a concentration calculated with the band-ratio OC4Me algorithm using in situ and IOP-calculated reflectance. Excluding Ch...
Kretzschmar, AL, Larsson, ME, Hoppenrath, M, Doblin, MA & Murray, SA 2019, 'Characterisation of Two Toxic Gambierdiscus spp. (Gonyaulacales, Dinophyceae) from the Great Barrier Reef (Australia): G. lewisii sp. nov. and G. holmesii sp. nov', PROTIST, vol. 170, no. 6.View/Download from: Publisher's site
Larsson, ME, Harwood, TD, Lewis, RJ, Himaya, SWA & Doblin, MA 2019, 'Toxicological characterization of Fukuyoa paulensis (Dinophyceae) from temperate Australia', Phycological Research, vol. 67, no. 1, pp. 65-71.View/Download from: Publisher's site
© 2018 Japanese Society of Phycology Dinoflagellates of the genus Gambierdiscus are known to produce neurotoxins that cause the human illness ciguatera, a tropical and sub-tropical fish poisoning. Some species from the Gambierdiscus genus were recently re-classified into a new genus, Fukuyoa based on their phylogenetic and morphological divergence, however, little is known about their distribution, ecology and toxicology. Here we report the first occurrence of F. paulensis in the temperate coastal waters of eastern Australia and characterize its toxicology. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) did not detect the presence of ciguatoxins, however, a putative maitotoxin congener (MTX-3) was present. Similarly, high maitotoxin-like activity was detected in High Performance Liquid Chromatography (HPLC) fractionated cell extracts using a Ca2+ influx bioassay on a Fluorescent Imaging Plate Reader (FLIPR), but no ciguatoxin-like activity was detected.
Larsson, ME, Smith, KF & Doblin, MA 2019, 'First description of the environmental niche of the epibenthic dinoflagellate species Coolia palmyrensis, C. malayensis, and C. tropicalis (Dinophyceae) from Eastern Australia.', Journal of phycology, vol. 55, no. 3, pp. 565-577.View/Download from: Publisher's site
Environmental variables such as temperature, salinity, and irradiance are significant drivers of microalgal growth and distribution. Therefore, understanding how these variables influence fitness of potentially toxic microalgal species is particularly important. In this study, strains of the potentially harmful epibenthic dinoflagellate species Coolia palmyrensis, C. malayensis, and C. tropicalis were isolated from coastal shallow water habitats on the east coast of Australia and identified using the D1-D3 region of the large subunit (LSU) ribosomal DNA (rDNA). To determine the environmental niche of each taxon, growth was measured across a gradient of temperature (15-30°C), salinity (20-38), and irradiance (10-200 μmol photons · m-2 · s-1 ). Specific growth rates of Coolia tropicalis were highest under warm temperatures (27°C), low salinities (ca. 23), and intermediate irradiance levels (150 μmol photons · m-2 · s-1 ), while C. malayensis showed the highest growth at moderate temperatures (24°C) and irradiance levels (150 μmol photons · m-2 · s-1 ) and growth rates were consistent across the range of salinity levels tested (20-38). Coolia palmyrensis had the highest growth rate of all species tested and favored moderate temperatures (24°C), oceanic salinity (35), and high irradiance (>200 μmol photons · m-2 · s-1 ). This is the first study to characterize the environmental niche of species from the benthic harmful algal bloom genus Coolia and provides important information to help define species distributions and inform risk management.
McInnes, AS, Laczka, OF, Baker, KG, Larsson, ME, Robinson, CM, Clark, JS, Laiolo, L, Alvarez, M, Laverock, B, Kremer, CT, van Sebille, E & Doblin, MA 2019, 'Live cell analysis at sea reveals divergent thermal performance between photosynthetic ocean microbial eukaryote populations.', The ISME journal, vol. 13, no. 5, pp. 1374-1378.View/Download from: Publisher's site
Experimentation at sea provides insight into which traits of ocean microbes are linked to performance in situ. Here we show distinct patterns in thermal tolerance of microbial phototrophs from adjacent water masses sampled in the south-west Pacific Ocean, determined using a fluorescent marker for reactive oxygen species (ROS). ROS content of pico-eukaryotes was assessed after 1, 5 and 25 h of incubation along a temperature gradient (15.6-32.1 °C). Pico-eukaryotes from the East Australian Current (EAC) had relatively constant ROS and showed greatest mortality after 25 h at 7 °C below ambient, whereas those from the Tasman Sea had elevated ROS in both warm and cool temperature extremes and greatest mortality at temperatures 6-10 °C above ambient, interpreted as the outcome of thermal stress. Tracking of water masses within an oceanographic circulation model showed populations had distinct thermal histories, with EAC pico-eukaryotes experiencing higher average temperatures for at least 1 week prior to sampling. While acclimatization and community assembly could both influence biological responses, this study clearly demonstrates that phenotypic divergence occurs along planktonic drift trajectories.
Coleman, MA, Clark, JS, Doblin, MA, Bishop, MJ & Kelaher, BP 2019, 'Genetic differentiation between estuarine and open coast ecotypes of a dominant ecosystem engineer', Marine and Freshwater Research, vol. 70, no. 7, pp. 977-985.View/Download from: Publisher's site
© CSIRO 2018. Temperate intertidal shores globally are often dominated by habitat-forming seaweeds, but our knowledge of these systems is heavily biased towards northern hemisphere species. Rocky intertidal shores throughout Australia and New Zealand are dominated by a single monotypic species, Hormosira banksii. This species plays a key role in facilitating biodiversity on both rocky shores and estuarine habitats, yet we know little about the processes that structure populations. Herein we characterise the genetic diversity and structure of Hormosira and demonstrate strong restrictions to gene flow over small spatial scales, as well as between estuarine and open coast populations. Estuarine ecotypes were often genetically unique from nearby open coast populations, possibly due to extant reduced gene flow between habitats, founder effects and coastal geomorphology. Deviations from random mating in many locations suggest complex demographic processes are at play within shores, including clonality in estuarine populations. Strong isolation by distance in Hormosira suggests that spatial management of intertidal habitats will necessitate a network of broad-scale protection. Understanding patterns of genetic diversity and gene flow in this important ecosystem engineer will enhance the ability to manage, conserve and restore this key species into the future.
Baker, KG, Radford, DT, Evenhuis, C, Kuzhiumparam, U, Ralph, PJ & Doblin, MA 2018, 'Thermal niche evolution of functional traits in a tropical marine phototroph.', Journal of phycology, vol. 54, no. 6, pp. 799-810.View/Download from: Publisher's site
Land-based plants and ocean-dwelling microbial phototrophs known as phytoplankton, are together responsible for almost all global primary production. Habitat warming associated with anthropogenic climate change has detrimentally impacted marine primary production, with the effects observed on regional and global scales. In contrast to slower-growing higher plants, there is considerable potential for phytoplankton to evolve rapidly with changing environmental conditions. The energetic constraints associated with adaptation in phytoplankton are not yet understood, but are central to forecasting how global biogeochemical cycles respond to contemporary ocean change. Here, we demonstrate a number of potential trade-offs associated with high-temperature adaptation in a tropical microbial eukaryote, Amphidinium massartii (dinoflagellate). Most notably, the population became high-temperature specialized (higher fitness within a narrower thermal envelope and higher thermal optimum), and had a greater nutrient requirement for carbon, nitrogen and phosphorus. Evidently, the energetic constraints associated with living at elevated temperature alter competiveness along other environmental gradients. While high-temperature adaptation led to an irreversible change in biochemical composition (i.e., an increase in fatty acid saturation), the mechanisms underpinning thermal evolution in phytoplankton remain unclear, and will be crucial to understanding whether the trade-offs observed here are species-specific or are representative of the evolutionary constraints in all phytoplankton.
Ajani, PA, Verma, A, Lassudrie, M, Doblin, MA & Murray, SA 2018, 'A new diatom species P. hallegraeffii sp. nov. belonging to the toxic genus Pseudo-nitzschia (Bacillariophyceae) from the East Australian Current.', PloS one, vol. 13, no. 4, pp. e0195622-e0195622.View/Download from: Publisher's site
A new species belonging to the toxin producing diatom genus Pseudo-nitzschia, P. hallegraeffii sp. nov., is delineated and described from the East Australian Current (EAC). Clonal cultures were established by single cell isolation from phytoplankton net hauls collected as part of a research expedition in the EAC region in 2016 on the RV Investigator. Cultures were assessed for their morphological and genetic characteristics, their sexual compatibility with other Pseudo-nitzschia species, and their ability to produce domoic acid. Light and transmission electron microscopy revealed cells which differed from their closest relatives by their cell width, rows of poroids, girdle band structure and density of band straie. Phylogenetic analyses based on sequencing of nuclear-encoded ribosomal deoxyribonucleic acid (rDNA) regions showed this novel genotype clustered within the P. delicatissima complex, but formed a discrete clade from its closest relatives P. dolorosa, P. simulans, P. micropora and P. delicatissima. Complementary base changes (CBCs) were observed in the secondary structure of the 3' nuclear ribosomal transcribed spacer sequence region (ITS2) between P. hallegraeffii sp. nov. and its closest related taxa, P. simulans and P. dolorosa. Under laboratory conditions, and in the absence of any zooplankton cues, strains of P. hallegraeffii sp. nov. did not produce domoic acid (DA) and were not sexually compatible with any other Pseudo-nitzschia clones tested. A total of 18 Pseudo-nitzschia species, including three confirmed toxigenic species (P. cuspidata, P. multistriata and P. australis) have now been unequivocally confirmed from eastern Australia.
Larsson, ME, Laczka, OF, Harwood, DT, Lewis, RJ, Himaya, SWA, Murray, SA & Doblin, MA 2018, 'Toxicology of Gambierdiscus spp. (Dinophyceae) from Tropical and Temperate Australian Waters.', Marine drugs, vol. 16, no. 1.View/Download from: Publisher's site
Ciguatera Fish Poisoning (CFP) is a human illness caused by the consumption of marine fish contaminated with ciguatoxins (CTX) and possibly maitotoxins (MTX), produced by species from the benthic dinoflagellate genus Gambierdiscus. Here, we describe the identity and toxicology of Gambierdiscus spp. isolated from the tropical and temperate waters of eastern Australia. Based on newly cultured strains, we found that four Gambierdiscus species were present at the tropical location, including G. carpenteri, G. lapillus and two others which were not genetically identical to other currently described species within the genus, and may represent new species. Only G. carpenteri was identified from the temperate location. Using LC-MS/MS analysis we did not find any characterized microalgal CTXs (P-CTX-3B, P-CTX-3C, P-CTX-4A and P-CTX-4B) or MTX-1; however, putative maitotoxin-3 (MTX-3) was detected in all species except for the temperate population of G. carpenteri. Using the Ca2+ influx SH-SY5Y cell Fluorescent Imaging Plate Reader (FLIPR) bioassay we found CTX-like activity in extracts of the unidentified Gambierdiscus strains and trace level activity in strains of G. lapillus. While no detectable CTX-like activity was observed in tropical or temperate strains of G. carpenteri, all species showed strong maitotoxin-like activity. This study, which represents the most comprehensive analyses of the toxicology of Gambierdiscus strains isolated from Australia to date, suggests that CFP in this region may be caused by currently undescribed ciguatoxins and maitotoxins.
Hughes, DJ, Campbell, DA, Doblin, MA, Kromkamp, JC, Lawrenz, E, Moore, CM, Oxborough, K, Prášil, O, Ralph, PJ, Alvarez, MF & Suggett, DJ 2018, 'Roadmaps and Detours: Active Chlorophyll- a Assessments of Primary Productivity Across Marine and Freshwater Systems.', Environmental science & technology, vol. 52, pp. 12039-12054.View/Download from: Publisher's site
Assessing phytoplankton productivity over space and time remains a core goal for oceanographers and limnologists. Fast Repetition Rate fluorometry (FRRf) provides a potential means to realize this goal with unprecedented resolution and scale yet has not become the "go-to" method despite high expectations. A major obstacle is difficulty converting electron transfer rates to equivalent rates of C-fixation most relevant for studies of biogeochemical C-fluxes. Such difficulty stems from methodological inconsistencies and our limited understanding of how the electron requirement for C-fixation (Φe,C) is influenced by the environment and by differences in the composition and physiology of phytoplankton assemblages. We outline a "roadmap" for limiting methodological bias and to develop a more mechanistic understanding of the ecophysiology underlying Φe,C. We 1) re-evaluate core physiological processes governing how microalgae invest photosynthetic electron transport-derived energy and reductant into stored carbon versus alternative sinks. Then, we 2) outline steps to facilitate broader uptake and exploitation of FRRf, which could transform our knowledge of aquatic primary productivity. We argue it is time to 3) revise our historic methodological focus on carbon as the currency of choice, to 4) better appreciate that electron transport fundamentally drives ecosystem biogeochemistry, modulates cell-to-cell interactions, and ultimately modifies community biomass and structure.
Hughes, DJ, Varkey, D, Doblin, MA, Ingleton, T, Mcinnes, A, Ralph, PJ, van Dongen-Vogels, V & Suggett, DJ 2018, 'Impact of nitrogen availability upon the electron requirement for carbon fixation in Australian coastal phytoplankton communities', Limnology and Oceanography, vol. 63, no. 5, pp. 1891-1910.View/Download from: Publisher's site
© 2018 Association for the Sciences of Limnology and Oceanography Nitrogen (N) availability affects phytoplankton photosynthetic performance and regulates marine primary production (MPP) across the global coast and oceans. Bio-optical tools including Fast Repetition Rate fluorometry (FRRf) are particularly well suited to examine MPP variability in coastal regions subjected to dynamic spatio-temporal fluctuations in nutrient availability. FRRf determines photosynthesis as an electron transport rate through Photosystem II (ETRPSII), requiring knowledge of an additional parameter, the electron requirement for carbon fixation (KC), to retrieve rates of CO2-fixation. KC strongly depends upon environmental conditions regulating photosynthesis, yet the importance of N-availability to this parameter has not been examined. Here, we use nutrient bioassays to isolate how N (relative to other macronutrients P, Si) regulates KC of phytoplankton communities from the Australian coast during summer, when N-availability is often highly variable. KC consistently responded to N-amendment, exhibiting up to a threefold reduction and hence an apparent increase in the efficiency with which electrons were used to drive C-fixation. However, the process driving this consistent reduction was dependent upon initial conditions. When diatoms dominated assemblages and N was undetectable (e.g., post bloom), KC decreased predominantly via a physiological adjustment of the existing community to N-amendment. Conversely, for mixed assemblages, N-addition achieved a similar reduction in KC through a change in community structure toward diatom domination. We generate new understanding and parameterization of KC that is particularly critical to advance how FRRf can be applied to examine C-uptake throughout the global ocean where nitrogen availability is highly variable and thus frequently limits primary productivity.
Larsson, M, Laczka, O, Suthers, I, Ajani, PA & Doblin, M 2018, 'Hitchhiking in the East Australian Current: rafting as a dispersal mechanism for harmful epibenthic dinoflagellates', Marine Ecology Progress Series.View/Download from: Publisher's site
Bouman, HA, Platt, T, Doblin, M, Figueiras, FG, Gudmundsson, K, Gudfinnsson, HG, Huang, B, Hickman, A, Hiscock, M, Jackson, T, Lutz, VA, Mélin, F, Rey, F, Pepin, P, Segura, V, Tilstone, GH, Van Dongen-Vogels, V & Sathyendranath, S 2018, 'Photosynthesis-irradiance parameters of marine phytoplankton: Synthesis of a global data set', Earth System Science Data, vol. 10, no. 1, pp. 251-266.View/Download from: Publisher's site
© Author(s) 2018. The photosynthetic performance of marine phytoplankton varies in response to a variety of factors, environmental and taxonomic. One of the aims of the MArine primary Production: model Parameters from Space (MAPPS) project of the European Space Agency is to assemble a global database of photosynthesis-irradiance (P-E) parameters from a range of oceanographic regimes as an aid to examining the basin-scale variability in the photophysiological response of marine phytoplankton and to use this information to improve the assignment of P-E parameters in the estimation of global marine primary production using satellite data. The MAPPS P-E database, which consists of over 5000 P-E experiments, provides information on the spatio-Temporal variability in the two P-E parameters (the assimilation number, PmB, and the initial slope, αB, where the superscripts B indicate normalisation to concentration of chlorophyll) that are fundamental inputs for models (satellite-based and otherwise) of marine primary production that use chlorophyll as the state variable. Quality-control measures consisted of removing samples with abnormally high parameter values and flags were added to denote whether the spectral quality of the incubator lamp was used to calculate a broad-band value of αB. The MAPPS database provides a photophysiological data set that is unprecedented in number of observations and in spatial coverage. The database will be useful to a variety of research communities, including marine ecologists, biogeochemical modellers, remote-sensing scientists and algal physiologists. The compiled data are available at https://doi.org/10.1594/PANGAEA.874087 (Bouman et al., 2017).
Clark, JS, Poore, AGB & Doblin, MA 2018, 'Shaping up for stress: Physiological flexibility is key to survivorship in a habitat-forming macroalga.', Journal of plant physiology, vol. 231, pp. 346-355.View/Download from: Publisher's site
Organisms from all domains of life can have highly variable morphologies, with this plasticity suggested to increase fitness and survivability under stressful conditions. Predicting how organisms will adapt to environmental change requires an understanding of how variable morphologies perform under environmental stress. Morphological plasticity has been documented within marine macroalgae inhabiting environmental gradients, however the functional consequences of this variation has been rarely tested. In this study, form-function was assessed in the habitat-forming, intertidal macroalga Hormosira banksii. Morphological variation was quantified on two spatial scales (tidal gradient versus latitudinal gradient) and the performance tested (relative water content and photosynthetic efficiency) of morphological variants during heat and desiccation stress. At regional scales, individuals at the warm distributional edge were overall smaller in size, and had smaller vesicles (higher surface area to volume ratio; SA:VOL) than those from central populations. At local scales, individuals high on the shore were generally shorter and had larger vesicles than those low on the shore. Vesicle morphology (SA:VOL) was found to predict relative water content and photosynthetic performance during desiccation and rehydration. Differences in SA:VOL of vesicles between heights on the shore may reflect water requirements needed to maintain tissue hydration for photosynthesis during low tide. Warm-edge populations showed increased thermal sensitivity as indicated by decreased photosynthetic yield of PSII and delays in recovery after desiccation. Sensitivities to higher temperatures amongst warm-edge populations are potentially due to smaller fluctuations in regional temperatures as well as their morphology. This study provides a mechanistic understanding of the morphological variation among H. banksii populations. It suggests that H. banksii has a high degree of morphological plasticity r...
Davies, CH, Ajani, P, Armbrecht, L, Atkins, N, Baird, ME, Beard, J, Bonham, P, Burford, M, Clementson, L, Coad, P, Crawford, C, Dela-Cruz, J, Doblin, MA, Edgar, S, Eriksen, R, Everett, JD, Furnas, M, Harrison, DP, Hassler, C, Henschke, N, Hoenner, X, Ingleton, T, Jameson, I, Keesing, J, Leterme, SC, McLaughlin, MJ, Miller, M, Moffatt, D, Moss, A, Nayar, S, Patten, NL, Patten, R, Pausina, SA, Proctor, R, Raes, E, Robb, M, Rothlisberg, P, Saeck, EA, Scanes, P, Suthers, IM, Swadling, KM, Talbot, S, Thompson, P, Thomson, PG, Uribe-Palomino, J, van Ruth, P, Waite, AM, Wright, S & Richardson, AJ 2018, 'A database of chlorophyll a in Australian waters', SCIENTIFIC DATA, vol. 5.View/Download from: Publisher's site
Laiolo, L, Matear, R, Baird, ME, Soja-Wozniak, M & Doblin, M 2018, 'Information content of in situ and remotely sensed chlorophyll-a: Learning from size-structured phytoplankton model', Journal of Marine Systems, vol. 183, pp. 1-12.View/Download from: Publisher's site
© 2018 Chlorophyll-a measurements in the form of in situ observations and satellite ocean colour products are commonly used in data assimilation to calibrate marine biogeochemical models. Here, a two size-class phytoplankton biogeochemical model, with a 0D configuration, was used to simulate the surface chlorophyll-a dynamics (simulated surface Chl-a) for cyclonic and anticyclonic eddies off East Australia. An optical model was then used to calculate the inherent optical properties from the simulation and convert them into remote-sensing reflectance (Rrs). Subsequently, Rrs was used to produce a satellite-like estimate of the simulated surface Chl-a concentrations through the MODIS OC3M algorithm (simulated OC3M Chl-a). Identical parameter optimisation experiments were performed through the assimilation of the two separate datasets (simulated surface Chl-a and simulated OC3M Chl-a), with the purpose of investigating the contrasting information content of simulated surface Chl-a and remotely-sensed data sources. The results we present are based on the analysis of the distribution of a cost function, varying four parameters of the biogeochemical model. In our idealized experiments the simulated OC3M Chl-a product is a poor proxy for the total simulated surface Chl-a concentration. Furthermore, our result show the OC3M algorithm can underestimate the simulated chlorophyll-a concentration in offshore eddies off East Australia (Case I waters), because of the weak relationship between large-sized phytoplankton and remote-sensing reflectance. Although Case I waters are usually characteristic of oligotrophic environments, with a photosynthetic community typically represented by relatively small-sized phytoplankton, mesoscale features such as eddies can generate seasonally favourable conditions for a photosynthetic community with a greater proportion of large phytoplankton cells. Furthermore, our results show that in mesoscale features such as eddies, in situ chlorophyll-...
Tian, C, Doblin, MA, Dafforn, KA, Johnston, EL, Pei, H & Hu, W 2018, 'Dinoflagellate cyst abundance is positively correlated to sediment organic carbon in Sydney Harbour and Botany Bay, NSW, Australia.', Environmental science and pollution research international, vol. 25, no. 6, pp. 5808-5821.View/Download from: Publisher's site
There is growing public concern about the global expansion of harmful algal bloom species (HABs), with dinoflagellate microalgae comprising the major portion of the harmful taxa. These motile, unicellular organisms have a lifecycle involving sexual reproduction and resting cyst formation whereby cysts can germinate from sediments and 'seed' planktonic populations. Thus, investigation of dinoflagellate cyst (dinocyst) distribution in sediments can provide significant insights into HAB dynamics and contribute to indices of habitat quality. Species composition and abundance of dinocysts in relation to sediment characteristics were studied at 18 stations in two densely populated temperate Australian estuaries, Sydney Harbour (Parramatta River/Port Jackson; PS) and Botany Bay (including Georges River; GB). Eighteen dinocyst taxa were identified, dominated by Protoceratium reticulatum and Gonyaulax sp.1 in the PS estuary, together with Archaeperidinium minutum and Gonyaulax sp.1 in the GB estuary. Cysts of Alexandrium catenella, which is one of the causative species of paralytic shellfish poisoning (PSP), were also detected in both estuaries. Out of the measured sediment characteristics (TOC, Cd, Cr, Cu, Fe, Pb, Mn, Ni, Zn and polycyclic aromatic hydrocarbons), TOC was the parameter explaining most of the variation in dinocyst assemblages and was positively correlated to most of the heavy metals. Given the significant relationship between sediment TOC and dinocyst abundance and heavy metal concentrations, this study suggests that sediment TOC could be broadly used in risk management for potential development of algal blooms and sediment contamination in these estuaries.
Tian, C, Hao, D, Pei, H, Doblin, MA, Ren, Y, Wei, J & Feng, Y 2018, 'Phytoplankton Functional Groups Variation and Influencing Factors in a Shallow Temperate Lake', WATER ENVIRONMENT RESEARCH, vol. 90, no. 6, pp. 510-519.View/Download from: Publisher's site
Larsson, M, Ajani, PA, Rubio, AM, Guise, K, MacPherson, RG, Brett, SJ, Davies, KP & Doblin, M 2017, 'Long-term perspective on the relationship between phytoplankton and nutrient concentrations in a southeastern Australian estuary', Marine Pollution Bulletin, vol. 114, no. 1, pp. 227-238.View/Download from: Publisher's site
Robinson, CM, Cherukuru, N, Hardman-Mountford, NJ, Everett, JD, McLaughlin, MJ, Davies, KP, van Dongen-Vogels, V, Ralph, PJ & Doblin, MA 2017, 'Phytoplankton absorption predicts patterns in primary productivity in Australian coastal shelf waters', Estuarine, Coastal and Shelf Science, vol. 192, pp. 1-16.View/Download from: Publisher's site
© 2017 Elsevier Ltd The phytoplankton absorption coefficient (a PHY ) has been suggested as a suitable alternate first order predictor of net primary productivity (NPP). We compiled a dataset of surface bio-optical properties and phytoplankton NPP measurements in coastal waters around Australia to examine the utility of an in-situ absorption model to estimate NPP. The magnitude of surface NPP (0.20–19.3 mmol C m −3 d −1 ) across sites was largely driven by phytoplankton biomass, with higher rates being attributed to the microplankton ( > 20 μm) size class. The phytoplankton absorption coefficient a PHY for PAR (photosynthetically active radiation; ā PHY )) ranged from 0.003 to 0.073 m -1 , influenced by changes in phytoplankton community composition, physiology and environmental conditions. The a PHY coefficient also reflected changes in NPP and the absorption model-derived NPP could explain 73% of the variability in measured surface NPP (n = 41; RMSE = 2.49). The absorption model was applied to two contrasting coastal locations to examine NPP dynamics: a high chlorophyll-high variation (HCHV; Port Hacking National Reference Station) and moderate chlorophyll-low variation (MCLV; Yongala National Reference Station) location in eastern Australia using the GIOP-DC satellite a PHY product. Mean daily NPP rates between 2003 and 2015 were higher at the HCHV site (1.71 ± 0.03 mmol C m −3 d −1 ) with the annual maximum NPP occurring during the austral winter. In contrast, the MCLV site annual NPP peak occurred during the austral wet season and had lower mean daily NPP (1.43 ± 0.03 mmol C m −3 d −1 ) across the time-series. An absorption-based model to estimate NPP is a promising approach for exploring the spatio-temporal dynamics in phytoplankton NPP around the Australian continental shelf.
Bellgrove, A, van Rooyen, A, Weeks, AR, Clark, JS, Doblin, MA & Miller, AD 2017, 'New resource for population genetics studies on the Australasian intertidal brown alga, Hormosira banksii: isolation and characterization of 15 polymorphic microsatellite loci through next generation DNA sequencing', Journal of Applied Phycology, vol. 29, no. 3, pp. 1721-1727.View/Download from: Publisher's site
© 2016, Springer Science+Business Media Dordrecht. The Australasian fucoid, Hormosira banksii, commonly known as 'Neptune's necklace' or 'bubbleweed' is regarded as an autogenic ecosystem engineer with no functional equivalents. Population declines resulting from climate change and other anthropogenic disturbances pose significant threats to intertidal biodiversity. For effective conservation strategies, patterns of gene flow and population genetic structure across the species distribution need to be clearly understood. We developed a suite of 15 polymorphic microsatellite markers using next generation sequencing of 53–55 individuals from two sites (south-western Victoria and central New South Wales, Australia) and a replicated spatially hierarchical sampling design. We observed low to moderate genetic variation across most loci (mean number of alleles per locus =3.26; mean expected heterozygosity =0.38) with no evidence of individual loci deviating significantly from Hardy-Weinberg equilibrium. Marker independence was confirmed with tests for linkage disequilibrium, and analyses indicated no evidence of null alleles across loci. Independent spatial autocorrelation analyses were performed for each site using multilocus genotypes and different relatedness measures. Both analyses indicated no significant patterns between relatedness and geographic distance, complemented by non-significant Hardy-Weinberg estimates (P < 0.05), suggesting that individuals from each site represent a randomly mating, outcrossing population. A preliminary investigation of population structure indicates that gene flow among sites is limited (F ST = 0.49), however more comprehensive sampling is needed to determine the extent of population structure across the species range ( > 10,000 km). The genetic markers described provide a valuable resource for future population genetic assessments that will help guide conservation planning for H. banksii and the associated intertidal communities.
McElroy, DJ, Hochuli, DF, Doblin, MA, Murphy, RJ, Blackburn, RJ & Coleman, RA 2017, 'Effect of copper on multiple successional stages of a marine fouling assemblage', BIOFOULING, vol. 33, no. 10, pp. 904-916.View/Download from: Publisher's site
van den Engh, GJ, Doggett, JK, Thompson, AW, Doblin, MA, Gimpel, CNG & Karl, DM 2017, 'Dynamics of Prochlorococcus and Synechococcus at station ALOHA revealed through flow cytometry and high-resolution vertical sampling', Frontiers in Marine Science, vol. 4, no. NOV.View/Download from: Publisher's site
© 2017 van den Engh, Doggett, Thompson, Doblin, Gimpel and Karl. The fluorescence and scattering properties of Prochlorococcus and Synechococcus at Station ALOHA as measured by flow cytometry (termed the FCM phenotype) vary with depth and over a variety of time scales. The variation in FCM phenotypes may reflect population selection or physiological acclimation to local conditions. Observations before, during, and after a storm with deep water mixing show a short-term homogenization of the FCM phenotypes with depth, followed by a return to the stable pattern over the time span of a few days. These dynamics indicate that, within the upper mixed-layer, the FCM phenotype distribution represents acclimation to ambient light. The populations in the pycnocline (around 100 m and below), remain stable and are invariant with light conditions. In samples where both cyanobacteria coexist, fluorescence properties of Prochlorococcus and Synechococcus are tightly correlated providing further evidence that FCM phenotype variability is caused by a common environmental factor or factors. Measurements of the dynamics of FCM phenotypes provide insights into phytoplankton physiology and adaptation. Alternatively, FCM phenotype census of a water mass may provide information about its origin and illumination history.
Baker, KG, Robinson, CM, Radford, DT, McInnes, AS, Evenhuis, C & Doblin, MA 2016, 'Thermal performance curves of functional traits aid understanding of thermally induced changes in diatom-mediated biogeochemical fluxes', Frontiers in Marine Science, vol. 3, pp. 1-14.View/Download from: Publisher's site
© 2016 Baker, Robinson, Radford, McInnes, Evenhuis and Doblin.How the functional traits (FTs) of phytoplankton change with temperature is important for understanding the impacts of ocean warming on phytoplankton mediated biogeochemical fluxes. This study quantifies the thermal performance curves (TPCs) of FTs in the cosmopolitan model diatom, Thalassiosira pseudonana, to advance understanding of trade-offs between physiological (photoacclimation, carbon fixation, nitrate, phosphate, and silicate uptake) and morphological traits (cell volume and frustule silicification). We show that each FT has substantial phenotypic plasticity and exhibits a unique TPC, varying in both shape and thermal optimum, and diverging from the growth response. The TPC for growth was symmetric with a thermal optimum (Topt) of 18°C. In comparison, the TPC for primary productivity was warm-skewed with a Topt around 21°C, whereas frustule silicification decreased linearly with increasing temperature. Together, this suggests that the optimal temperature for overall fitness is a balance of trade-offs in the underlying functional traits. Moreover, these results demonstrate that growth is not necessarily an accurate estimate of overall biogeochemical performance and that temperature change will likely influence elemental fluxes such as carbon and silicon. Finally, we show that temperature-driven changes in individual traits e.g., photoacclimation, can mimic responses experienced under other environmental stressors (high light) and so a multi-trait assessment is essential for accurate interpretation of the cellular impact of warming. This study also reveals that multi-trait analysis, in the context of TPCs, provides insight into the cellular physiology regulating the whole cell response and has the potential to provide better estimates of how diatom-mediated biogeochemical fluxes are likely to be impacted in the context of ocean warming. Analyzing the response of multiple traits more comprehensiv...
Doblin, MA, Petrou, K, Sinutok, S, Seymour, JR, Messer, LF, Brown, MV, Norman, L, Everett, JD, McInnes, AS, Ralph, PJ, Thompson, PA & Hassler, CS 2016, 'Nutrient uplift in a cyclonic eddy increases diversity, primary productivity and iron demand of microbial communities relative to a western boundary current', PEERJ, vol. 4.View/Download from: Publisher's site
Jeffries, TC, Curlevski, NJ, Brown, MV, Harrison, DP, Doblin, MA, Petrou, K, Ralph, PJ & Seymour, JR 2016, 'Partitioning of fungal assemblages across different marine habitats', ENVIRONMENTAL MICROBIOLOGY REPORTS, vol. 8, no. 2, pp. 235-238.View/Download from: Publisher's site
Messer, LF, Mahaffey, C, Robinson, CM, Jeffries, TC, Baker, KG, Bibiloni Isaksson, J, Ostrowski, M, Doblin, MA, Brown, MV & Seymour, JR 2016, 'High levels of heterogeneity in diazotroph diversity and activity within a putative hotspot for marine nitrogen fixation.', The ISME journal, vol. 10, pp. 1499-1513.View/Download from: Publisher's site
Australia's tropical waters represent predicted 'hotspots' for nitrogen (N2) fixation based on empirical and modelled data. However, the identity, activity and ecology of diazotrophs within this region are virtually unknown. By coupling DNA and cDNA sequencing of nitrogenase genes (nifH) with size-fractionated N2 fixation rate measurements, we elucidated diazotroph dynamics across the shelf region of the Arafura and Timor Seas (ATS) and oceanic Coral Sea during Austral spring and winter. During spring, Trichodesmium dominated ATS assemblages, comprising 60% of nifH DNA sequences, while Candidatus Atelocyanobacterium thalassa (UCYN-A) comprised 42% in the Coral Sea. In contrast, during winter the relative abundance of heterotrophic unicellular diazotrophs (δ-proteobacteria and γ-24774A11) increased in both regions, concomitant with a marked decline in UCYN-A sequences, whereby this clade effectively disappeared in the Coral Sea. Conservative estimates of N2 fixation rates ranged from <1 to 91 nmol l(-1) day(-1), and size fractionation indicated that unicellular organisms dominated N2 fixation during both spring and winter, but average unicellular rates were up to 10-fold higher in winter than in spring. Relative abundances of UCYN-A1 and γ-24774A11 nifH transcripts negatively correlated to silicate and phosphate, suggesting an affinity for oligotrophy. Our results indicate that Australia's tropical waters are indeed hotspots for N2 fixation and that regional physicochemical characteristics drive differential contributions of cyanobacterial and heterotrophic phylotypes to N2 fixation.The ISME Journal advance online publication, 27 November 2015; doi:10.1038/ismej.2015.205.
Murray, SA, Suggett, DJ, Seymour, JR, Doblin, M, Kohli, GS, Fabris, M & Ralph, PJ 2016, 'Unravelling the functional genetics of dinoflagellates: a review of approaches and opportunities', Perspectives in Phycology, vol. 3, no. 1, pp. 37-52.View/Download from: Publisher's site
Dinoflagellates occupy an extraordinarily diverse array of ecological niches. Their success stems from a suite of functional and ecological strategies, including the production of secondary metabolites with anti-predator or allelopathic impacts, nutritional flexibility, and the ability to form symbiotic relationships. Despite their ecological importance, we currently have a poor understanding of the genetic basis for many of these strategies, due to the complex genomes of dinoflagellates. Genomics and transcriptomic sequencing approaches are now providing the first insights into the genetic basis of some dinoflagellate functional traits, providing the opportunity for novel ecological experiments, novel methods for monitoring of harmful biotoxins, and allowing us to investigate the production of ecologically and economically important compounds such as the long chain polyunsaturated fatty acid, docosahexanoic acid and the climatically important metabolite, dimethylsulfoniopropionate. Despite these advances, we still generally lack the ability to genetically manipulate species, which would enable the confirmation of biosynthetic pathways and the development of novel bio-engineering applications. Here, we describe advances in understanding the genetic basis of dinoflagellate ecology, and propose biotechnological approaches that could be applied to further transform our understanding of this unique group of eukaryotes.
Ros, M, Pernice, M, Le Guillou, S, Doblin, MA, Schrameyer, V & Laczka, O 2016, 'Colorimetric detection of caspase 3 activity and reactive oxygen derivatives: Potential early indicators of thermal stress in corals', Journal of Marine Biology, vol. 2016, pp. 1-11.View/Download from: Publisher's site
© 2016 Mickael Ros et al. There is an urgent need to develop and implement rapid assessments of coral health to allow effective adaptive management in response to coastal development and global change. There is now increasing evidence that activation of caspase-dependent apoptosis plays a key role during coral bleaching and subsequent mortality. In this study, a "clinical" approach was used to assess coral health by measuring the activity of caspase 3 using a commercial kit. This method was first applied while inducing thermal bleaching in two coral species, Acropora millepora and Pocillopora damicornis. The latter species was then chosen to undergo further studies combining the detection of oxidative stress-related compounds (catalase activity and glutathione concentrations) as well as caspase activity during both stress and recovery phases. Zooxanthellae photosystem II (PSII) efficiency and cell density were measured in parallel to assess symbiont health. Our results demonstrate that the increased caspase 3 activity in the coral host could be detected before observing any significant decrease in the photochemical efficiency of PSII in the algal symbionts and/or their expulsion from the host. This study highlights the potential of host caspase 3 and reactive oxygen species scavenging activities as early indicators of stress in individual coral colonies.
Sackett, O, Petrou, K, Reedy, B, Hill, R, Doblin, M, Beardall, J, Ralph, P & Heraud, P 2016, 'Snapshot prediction of carbon productivity, carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy.', The ISME journal, vol. 10, pp. 416-426.View/Download from: Publisher's site
Diatoms, an important group of phytoplankton, bloom annually in the Southern Ocean, covering thousands of square kilometers and dominating the region's phytoplankton communities. In their role as the major food source to marine grazers, diatoms supply carbon, nutrients and energy to the Southern Ocean food web. Prevailing environmental conditions influence diatom phenotypic traits (for example, photophysiology, macromolecular composition and morphology), which in turn affect the transfer of energy, carbon and nutrients to grazers and higher trophic levels, as well as oceanic biogeochemical cycles. The paucity of phenotypic data on Southern Ocean phytoplankton limits our understanding of the ecosystem and how it may respond to future environmental change. Here we used a novel approach to create a 'snapshot' of cell phenotype. Using mass spectrometry, we measured nitrogen (a proxy for protein), total carbon and carbon-13 enrichment (carbon productivity), then used this data to build spectroscopy-based predictive models. The models were used to provide phenotypic data for samples from a third sample set. Importantly, this approach enabled the first ever rate determination of carbon productivity from a single time point, circumventing the need for time-series measurements. This study showed that Chaetoceros simplex was less productive and had lower protein and carbon content during short-term periods of high salinity. Applying this new phenomics approach to natural phytoplankton samples could provide valuable insight into understanding phytoplankton productivity and function in the marine system.The ISME Journal advance online publication, 31 July 2015; doi:10.1038/ismej.2015.123.
Cherukuru, N, Davies, PL, Brando, VE, Anstee, JM, Baird, ME, Clementson, LA & Doblin, MA 2016, 'Physical oceanographic processes influence bio-optical properties in the Tasman Sea', JOURNAL OF SEA RESEARCH, vol. 110, pp. 1-7.View/Download from: Publisher's site
Doblin, MA & van Sebille, E 2016, 'Drift in ocean currents impacts intergenerational microbial exposure to temperature', Proceedings of the National Academy of Sciences of USA, vol. 113, no. 20, pp. 5700-7505.View/Download from: Publisher's site
Microbes are the foundation of marine ecosystems [Falkowski PG, Fenchel T, Delong EF (2008) Science 320(5879):1034–1039]. Until now, the analytical framework for understanding the implications of ocean warming on microbes has not considered thermal exposure during transport in dynamic seascapes, implying that our current view of change for these critical organisms may be inaccurate. Here we show that upper-ocean microbes experience along-trajectory temperature variability up to 10 °C greater than seasonal fluctuations estimated in a static frame, and that this variability depends strongly on location. These findings demonstrate that drift in ocean currents can increase the thermal exposure of microbes and suggests that microbial populations with broad thermal tolerance will survive transport to distant regions of the ocean and invade new habitats. Our findings also suggest that advection has the capacity to influence microbial community assemblies, such that regions with strong currents and large thermal fluctuations select for communities with greatest plasticity and evolvability, and communities with narrow thermal performance are found where ocean currents are weak or along-trajectory temperature variation is low. Given that fluctuating environments select for individual plasticity in microbial lineages, and that physiological plasticity of ancestors can predict the magnitude of evolutionary responses of subsequent generations to environmental change [Schaum CE, Collins S (2014) Proc Biol Soc 281(1793):20141486], our findings suggest that microbial populations in the sub-Antarctic (∼40°S), North Pacific, and North Atlantic will have the most capacity to adapt to contemporary ocean warming.
Laiolo, L, McInnes, AS, Matear, R & Doblin, MA 2016, 'Key Drivers of Seasonal Plankton Dynamics in Cyclonic and Anticyclonic Eddies off East Australia', Frontiers in Marine Science, vol. 3, no. 155, pp. 1-14.View/Download from: Publisher's site
McElroy, D, Doblin, MA, Murphy, R, Hochuli, D & Coleman, R 2016, 'A limited legacy effect of copper in marine biofilms', Marine Pollution Bulletin, vol. 109, no. 1, pp. 117-127.View/Download from: Publisher's site
The effects of confounding by temporal factors remains understudied in pollution ecology. For example, there is little understanding of how disturbance history affects the development of assemblages. To begin addressing this gap in knowledge, marine biofilms were subjected to temporally-variable regimes of copper exposure and depuration. It was expected that the physical and biological structure of the biofilms would vary in response to copper regime. Biofilms were examined by inductively coupled plasma optical emission spectrometry, chlorophyll-a fluorescence and field spectrometry and it was found that (1) concentrations of copper were higher in those biofilms exposed to copper, (2) concentrations of copper remain high in biofilms after the source of copper is removed, and (3) exposure to and depuration from copper might have comparable effects on the photosynthetic microbial assemblages in biofilms. The persistence of copper in biofilms after depuration reinforces the need for consideration of temporal factors in ecology.
Hong, Y, Burford, MA, Ralph, PJ & Doblin, MA 2015, 'Subtropical zooplankton assemblage promotes the harmful cyanobacterium Cylindrospermopsis raciborskii in a mesocosm experiment', JOURNAL OF PLANKTON RESEARCH, vol. 37, no. 1, pp. 90-101.View/Download from: Publisher's site
Everett, JD & Doblin, MA 2015, 'Characterising primary productivity measurements across a dynamic western boundary current region', DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, vol. 100, pp. 105-116.View/Download from: Publisher's site
Hassler, CS, Norman, L, Nichols, CAM, Clementson, LA, Robinson, C, Schoemann, V, Watson, RJ & Doblin, MA 2015, 'Iron associated with exopolymeric substances is highly bioavailable to oceanic phytoplankton', MARINE CHEMISTRY, vol. 173, pp. 136-147.View/Download from: Publisher's site
Henschke, N, Everett, JD, Suthers, IM, Smith, JA, Hunt, BPV, Doblin, MA & Taylor, MD 2015, 'Zooplankton trophic niches respond to different water types of the western Tasman Sea: A stable isotope analysis', DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, vol. 104, pp. 1-8.View/Download from: Publisher's site
Johnston, EL, Mayer-Pinto, M, Hutchings, PA, Marzinelli, EM, Ahyong, ST, Birch, G, Booth, DJ, Creese, RG, Doblin, MA, Figueira, W, Gribben, PE, Pritchard, T, Roughan, M, Steinberg, PD & Hedge, LH 2015, 'Sydney Harbour: what we do and do not know about a highly diverse estuary', MARINE AND FRESHWATER RESEARCH, vol. 66, no. 12, pp. 1073-1087.View/Download from: Publisher's site
Jones, EM, Doblin, MA, Matear, R & King, E 2015, 'Assessing and evaluating the ocean-colour footprint of a regional observing system', JOURNAL OF MARINE SYSTEMS, vol. 143, pp. 49-61.View/Download from: Publisher's site
Mayer-Pinto, M, Johnston, EL, Hutchings, PA, Marzinelli, EM, Ahyong, ST, Birch, G, Booth, DJ, Creese, RG, Doblin, MA, Figueira, W, Gribben, PE, Pritchard, T, Roughan, M, Steinberg, PD & Hedge, LH 2015, 'Sydney Harbour: a review of anthropogenic impacts on the biodiversity and ecosystem function of one of the world's largest natural harbours', MARINE AND FRESHWATER RESEARCH, vol. 66, no. 12, pp. 1088-1105.View/Download from: Publisher's site
Thompson, PA, Bonham, P, Thomson, P, Rochester, W, Doblin, MA, Waite, AM, Richardson, A & Rousseaux, CS 2015, 'Climate variability drives plankton community composition changes: the 2010-2011 El Nino to La Nina transition around Australia', JOURNAL OF PLANKTON RESEARCH, vol. 37, no. 5, pp. 966-984.View/Download from: Publisher's site
Tian, C, Pei, H, Hu, W, Hao, D, Doblin, MA, Ren, Y, Wei, J & Feng, Y 2015, 'Variation of phytoplankton functional groups modulated by hydraulic controls in Hongze Lake, China', ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH, vol. 22, no. 22, pp. 18163-18175.View/Download from: Publisher's site
Laczka, OF, Labbate, M & Doblin, MA 2014, 'Application of an ELISA-type amperometric assay to the detection of Vibrio species with screenprinted electrodes', Analytical Methods, vol. 6, pp. 2020-2023.View/Download from: Publisher's site
Laczka, OF, Labbate, M, Seymour, JR, Bourne, DG, Fielder, SS & Doblin, MA 2014, 'Surface Immuno-Functionalisation for the Capture and Detection of Vibrio Species in the Marine Environment: A New Management Tool for Industrial Facilities', PLOS ONE, vol. 9, no. 10.View/Download from: Publisher's site
Robinson, C, Suggett, DJ, Cherukuru, N, Ralph, PJ & Doblin, MA 2014, 'Performance of Fast Repetition Rate fluorometry based estimates of primary productivity in coastal waters', JOURNAL OF MARINE SYSTEMS, vol. 139, pp. 299-310.View/Download from: Publisher's site
Hassler, CS, Ridgway, K, Bowie, AR, Butler, EC, Clementson, L, Doblin, MA, Davies, DM, Law, C, Ralph, PJ, van der Merwe, P, Watson, R & Ellwood, M 2014, 'Primary productivity induced by iron and nitrogen in the Tasman Sea - An overview of the PINTS expedition', Marine and Freshwater Research, vol. 65, no. 6, pp. 517-537.View/Download from: Publisher's site
The Tasman Sea and the adjacent Sub-Antarctic zone (SAZ) are economically important regions, where the parameters controlling the phytoplankton community composition and carbon fixation are not yet fully resolved. Contrasting nutrient distributions as well as phytoplankton biomass, biodiversity and productivity we observed between the North Tasman Sea and the SAZ. In-situ FV/FM, dissolved and particulate nutrients, iron biological uptake, and nitrogen and carbon fixation were used to determine the factor limiting phytoplankton growth and productivity in the North Tasman Sea and the SAZ. Highly productive cyanobacteria dominated the North Tasman Sea. High atmospheric nitrogen fixation and low nitrate dissolved concentrations indicated that non-diazotroph phytoplankton are nitrogen limited. Deck-board incubations also suggested that, at depth, iron could limit eukaryotes, but not cyanobacteria in that region. In the SAZ, the phytoplankton community was dominated by a bloom of haptophytes. The low productivity in the SAZ was mainly explained by light limitation, but nitrogen, silicic acid as well as iron were all depleted to the extent that they could become co-limiting. This study illustrates the challenge associated with identification of the limiting nutrient as it varied between phytoplankton groups, depths and sites.
Sackett, O, Armand, L, Beardall, J, Hill, R, Doblin, M, Connelly, C, Howes, J, Stuart, B, Ralph, P & Heraud, P 2014, 'Taxon-specific responses of Southern Ocean diatoms to Fe enrichment revealed by synchrotron radiation FTIR microspectroscopy', Biogeosciences Discussions, vol. 11, no. 20, pp. 5795-5808.View/Download from: Publisher's site
Photosynthesis by marine diatoms contributes substantially to global biogeochemical cycling and ecosystem productivity. It is widely accepted that diatoms are extremely sensitive to changes in Fe availability, with numerous in situ experiments demonstrating rapid growth and increased export of elements (e.g. C, Si and Fe) from surface waters as a result of Fe addition. Less is known about the effects of Fe enrichment on the phenotypes of diatoms, such as associated changes in nutritional value – furthermore, data on taxon-specific responses are almost non-existent. Enhanced supply of nutrient-rich waters along the coast of the subantarctic Kerguelen Island provide a valuable opportunity to examine the responses of phytoplankton to natural Fe enrichment. Here we demonstrate the use of synchrotron radiation Fourier Transform Infrared (SR-FTIR) microspectroscopy to analyse changes in the macromolecular composition of diatoms collected along the coast and plateau of Kerguelen Island, Southern Ocean. SR-FTIR microspectroscopy enabled the analysis of individual diatom cells from mixed communities of field-collected samples, thereby providing insight into in situ taxon-specific responses in relation to changes in Fe availability. Phenotypic responses were taxon-specific in terms of intraspecific variability and changes in proteins, amino acids, phosphorylated molecules, silicate/silicic acid and carbohydrates. In contrast to some previous studies, silicate/silicic acid levels increased under Fe enrichment, in conjunction with increases in carbohydrate stores. The highly abundant taxon Fragilariopsis kerguelensis displayed a higher level of phenotypic plasticity than Pseudo-nitzschia spp., while analysis of the data pooled across all measured taxa showed different patterns in macromolecular composition compared to those for individual taxon. This study demonstrates that taxon-specific responses to Fe enrichment may not always be accurately reflected by bulk community mea...
Sinutok, S, Hill, R, Kuhl, M, Doblin, MA & Ralph, PJ 2014, 'Ocean acidification and warming alter photosynthesis and calcification of the symbiont-bearing foraminifera Marginopora vertebralis', Marine Biology, vol. 161, pp. 2143-2154.View/Download from: Publisher's site
Everett, J, Baird, ME, Roughan, M, Suthers, I & Doblin, MA 2014, 'Relative impact of seasonal and oceanographic drivers on surface chlorophyll a along a Western Boundary Current', Progress in Oceanography, vol. 120, pp. 340-351.View/Download from: Publisher's site
Strengthening Western Boundary Currents (WBCs) advect warm, low nutrient waters into temperate latitudes, displacing more productive waters. WBCs also influence phytoplankton distribution and growth through current-induced upwelling, mesoscale eddy intrusion and seasonal changes in strength and poleward penetration. Here we examine dynamics of chlorophyll a (Chl. a) in the western Pacific Ocean, a region strongly influenced by the East Australian Current (EAC). We interpreted a spatial and temporal analysis of satellite-derived surface Chl. a, using a hydrodynamic model, a wind-reanalysis product and an altimetry-derived eddy-census. Our analysis revealed regions of persistently elevated surface Chl. a along the continental shelf and showed that different processes have a dominant effect in different locations. In the northern and central zones, upwelling events tend to regulate surface Chl. a patterns, with peaks in phytoplankton biomass corresponding to two known upwelling locations south of Cape Byron (28.5S) and Smoky Cape (31S). Within the central EAC separation zone, positive surface Chl. a anomalies occurred 65% of the time when both wind-stress (sw) and bottom-stress (sB) were upwelling- favourable, and only 17% of the time when both were downwelling-favourable. The interaction of wind and the EAC was a critical driver of surface Chl. a dynamics, with upwelling-favourable sW resulting in a 70% increase in surface Chl. a at some locations, when compared to downwelling-favourable sW. In the southern zone, surface Chl. a was driven by a strong seasonal cycle, with phytoplankton biomass increasing up to 152% annually each spring. The Stockton Bight region (32.2533.25S) contained P20% of the total shelf Chl. a on 27% of occasions due to its location downstream of upwelling locations, wide shelf area and reduced surface velocities. This region is analogous to productive fisheries regions in the Aghulus Current (Natal Bight) and Kuroshio Current (Enshu-nada Sea)...
Henschke, N, Everett, J, Doblin, MA, Pitt, K, Richardson, AJ & Suthers, IM 2014, 'Demography and interannual variability of salp swarms (Thalia democratica)', Marine Biology, vol. 161, no. 1, pp. 149-163.View/Download from: Publisher's site
Swarms of the pelagic tunicate, Thalia democratica, form during spring, but the causes of the large interannual variability in the magnitude of salp swarms are unclear. Changes in asexual reproduction (buds per chain) of T. democratica populations in the coastal waters of south-east Australia (3235°S) were observed in three austral springs (October 20082010). T. democratica abundance was significantly higher in 2008 (1,312 individuals m-3) than 2009 and 2010 (210 and 92 individuals m-3, respectively). There was a significant negative relationship (linear regression, r 2 = 0.61, F 1,22 = 33.83, P < 0.001) between abundance and asexual reproduction. Similarly, relative growth rates declined with decreasing abundance. Generalised additive mixed modelling showed that T. democratica abundance was significantly positively related to preferred food >2 µm in size (P < 0.05) and negatively related to the proportion of non-salp zooplankton (P < 0.001). Salp swarm magnitude, growth, and asexual reproduction may depend on the abundance of larger phytoplankton (prymnesiophytes and diatoms) and competition with other zooplankton.
Henschke, N, Everett, JD, Doblin, MA, Pitt, KA, Richardson, AJ & Suthers, IM 2014, 'Demography and interannual variability of salp swarms (Thalia democratica)', Marine Biology, vol. 161, no. 1, pp. 149-163.View/Download from: Publisher's site
Sackett, O, Armand, L, Beardall, J, Hill, R, Doblin, M, Connelly, C, Howes, J, Stuart, B, Ralph, P & Heraud, P 2014, 'Taxon-specific responses of Southern Ocean diatoms to Fe enrichment revealed by synchrotron radiation FTIR microspectroscopy', Biogeosciences Discussions, vol. 11, no. 5, pp. 7327-7357.View/Download from: Publisher's site
Photosynthesis by marine diatoms contributes substantially to global biogeochemical cycling and ecosystem productivity. It is widely accepted that diatoms are extremely sensitive to changes in Fe availability, with numerous in situ experiments demonstrating rapid growth and increased export of elements (e.g. C, Si and Fe) from surface waters as a result of Fe addition. Less is known about the effects of Fe enrichment on the phenotypes of diatoms, such as associated changes in nutritional value, furthermore data on taxon-specific responses is almost non-existent. Enhanced supply of nutrient-rich waters along the coast of the subantarctic Kerguelen Island provide a valuable opportunity to examine the responses of phytoplankton to natural Fe enrichment. Here we demonstrate the use of synchrotron radiation Fourier Transform Infrared (SR-FTIR) microspectroscopy to analyse changes in the macromolecular composition of diatoms collected along the coast and plateau of Kerguelen Island, Southern Ocean. SR-FTIR microspectroscopy enabled the analysis of individual diatom cells from mixed communities of field-collected samples, thereby providing insight into in situ taxon-specific responses in relation to changes in Fe availability. Phenotypic responses were taxon-specific in terms of intraspecific variability and changes in proteins, amino acids, phosphorylated molecules, silicate and carbohydrates. In contrast to some previous studies, silicate levels increased under Fe enrichment, in conjunction with increases in carbohydrate stores. The highly abundant taxon <i>Fragilariopsis kerguelensis</i> displayed a higher level of phenotypic plasticity than <i>Pseudo-nitzschia</i> spp., while analysis of the data pooled across all measured taxa showed different patterns in macromolecular composition compared to those for individual taxon. This study demonstrates that taxon-specific responses to Fe enrichment may not always be accurately reflected by b...
Clark, J, Poore, AG, Ralph, PJ & Doblin, MA 2013, 'Potential for adaptation in response to thermal stress in an intertidal macroalga', Journal of Phycology, vol. 49, no. 4, pp. 630-639.View/Download from: Publisher's site
Understanding responses of marine algae to changing ocean temperatures requires knowledge of the impacts of elevated temperatures and the likelihood of adaptation to thermal stress. The potential for rapid evolution of thermal tolerance is dependent on the levels of heritable genetic variation in response to thermal stress within a population. Here, we use a quantitative genetic breeding design to establish whether there is a heritable variation in thermal sensitivity in two populations of a habitat-forming intertidal macroalga, Hormosira banksii (Turner) Descaisne. Gametes from multiple parents were mixed and growth and photosynthetic performance were measured in the resulting embryos, which were incubated under control and elevated temperature (20°C and 28°C). Embryo growth was reduced at 28°C, but significant interactions between male genotype and temperature in one population indicated the presence of genetic variation in thermal sensitivity. Selection for more tolerant genotypes thus has the ability to result in the evolution of increased thermal tolerance. Furthermore, genetic correlations between embryos grown in the two temperatures were positive, indicating that those genotypes that performed well in elevated temperature also performed well in control temperature. Chlorophyll a fluorescence measurements showed a marked decrease in maximum quantum yield of photosystem II (PSII) under elevated temperature. There was an increase in the proportion of energy directed to photoinhibition (nonregulated nonphotochemical quenching) and a concomitant decrease in energy used to drive photochemistry and xanthophyll cycling (regulated nonphotochemical quenching). However, PSII performance between genotypes was similar, suggesting that thermal sensitivity is related to processes other than photosynthesis.
Hong, Y, Burford, MA, Ralph, PJ, Udy, JW & Doblin, MA 2013, 'The cyanobacterium Cylindrospermopsis raciborskii is facilitated by copepod selective grazing', Harmful Algae, vol. 29, no. 1, pp. 14-21.View/Download from: Publisher's site
Blooms of the toxin-producing cyanobacterium Cylindrospermopsis raciborskii occur in tropical and subtropical lakes during spring-summer but the mechanisms behind bloom formation are unclear. This study tests the hypothesis that C. raciborskii accumulations in freshwater systems are facilitated by selective copepod grazing. Prey selection was examined in a series of experiments with C. raciborskii and the green alga, Chlamydomonas reinhardtii, as well as within natural phytoplankton assemblages. Clearance rates of the copepod Boeckella sp. on a C. raciborskii diet were 24 times lower than that of a common cladoceran Ceriodaphnia sp. when both grazers had prey choice. More C. raciborskii was cleared by Boeckella sp. when in mixed natural phytoplankton assemblages, but the clearance rate declined when nutrient replete C. reinhardtii was added, demonstrating that when alternate high quality algae were present, so did C. raciborskii consumption. The clearance rates of Boeckella sp. on two toxic C. raciborskii strains were significantly lower than on a non-toxic strain, and on C. raciborskii with low cellular P content. When we tested the grazing preference of a copepod dominated mixed zooplankton community on C. raciborskii during the early bloom period, clearance rates were relatively low (0.050.20 ml individual-1 h-1), and decreased significantly as the proportion of C. raciborskii increased above 5%. These results suggest that C. raciborskii persistence could be promoted by copepods preferentially grazing on other algae, with significant loss of top-down control as C. raciborskii abundance increases.
Sackett, O, Petrou, K, Reedy, B, De Grazia, A, Hill, R, Doblin, M, Beardall, J, Ralph, P & Heraud, P 2013, 'Phenotypic Plasticity of Southern Ocean Diatoms: Key to Success in the Sea Ice Habitat?', PLOS ONE, vol. 8, no. 11.View/Download from: Publisher's site
Sinutok, S, Hill, R, Doblin, MA & Ralph, PJ 2013, 'Diurnal photosynthetic response of the motile symbiotic benthic foraminiferan Marginopora vertebralis', Marine Ecology Progress Series, vol. 478, pp. 127-138.View/Download from: Publisher's site
Movement of the symbiont-bearing foraminiferan Marginopora vertebralis and photo physiological response to diurnal fluctuations in irradiance were investigated in field and laboratory experiments. The abundance of M. vertebralis from both light-exposed and sheltered habitats was determined 5 times during the day, from pre-dawn to post-dusk. M. vertebralis abundance was significantly higher in sheltered compared to exposed habitats at midday under high irradiance, and this movement enabled the algal symbionts to avoid excessive photoinhibition. The diurnal changes in photosynthetic efficiency were not consistent with the typical midday solar maximum downregulation of photosystem II observed in other photoautotrophs and was likely due to the negatively phototactic capacity of the foraminifera. To confirm the light-dependent movement of foraminifera, individuals in exposed and sheltered habitats were exposed to the photosynthetic inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) in the laboratory. The lack of movement in DCMU-exposed specimens confirmed light-dependent movement and subsequent disruption of signalling between the host foraminiferan and the algal symbionts. Analysis of chlorophyll and xanthophyll pigments, as well as symbiont density, indicated that under high irradiance, foraminiferal symbionts have the capacity to reduce light stress by activating photo-protective mechanisms. The negatively phototactic behaviour prevented chlorophyll degradation, symbiont loss and bleaching, suggesting that it is the primary mechanism for controlling light exposure in these foraminifera. This behaviour provides a competitive advantage over other sessile organisms in avoiding photoinhibition and bleaching by moving away from over-saturating irradiance, towards less damaging light fields.
Dafforn, KA, Kelaher, BP, Simpson, SL, Coleman, MA, Hutchings, PA, Clark, GF, Knott, NA, Doblin, MA & Johnston, EL 2013, 'Polychaete richness and abundance enhanced in anthropogenically modified estuaries despite high concentrations of toxic contaminants', PLoS One, vol. 8, no. 9, pp. 1-10.View/Download from: Publisher's site
Ecological communities are increasingly exposed to multiple chemical and physical stressors, but distinguishing anthropogenic impacts from other environmental drivers remains challenging. Rarely are multiple stressors investigated in replicated studies over large spatial scales (.1000 kms) or supported with manipulations that are necessary to interpret ecological patterns. We measured the composition of sediment infaunal communities in relation to anthropogenic and natural stressors at multiple sites within seven estuaries. We observed increases in the richness and abundance of polychaete worms in heavily modified estuaries with severe metal contamination, but no changes in the diversity or abundance of other taxa. Estuaries in which toxic contaminants were elevated also showed evidence of organic enrichment. We hypothesised that the observed response of polychaetes was not a `positive response to toxic contamination or a reduction in biotic competition, but due to high levels of nutrients in heavily modified estuaries driving productivity in the water column and enriching the sediment over large spatial scales. We deployed defaunated field-collected sediments from the surveyed estuaries in a small scale experiment, but observed no effects of sediment characteristics (toxic or enriching). Furthermore, invertebrate recruitment instead reflected the low diversity and abundance observed during field surveys of this relatively `pristine estuary. This suggests that differences observed in the survey are not a direct consequence of sediment characteristics (even severe metal contamination) but are related to parameters that covary with estuary modification such as enhanced productivity from nutrient inputs and the diversity of the local species pool. This has implications for the interpretation of diversity measures in large-scale monitoring studies in which the observed patterns may be strongly influenced by many factors that covary with anthropogenic modification.
Gobler, CJ, Lobanov, AV, Tang, Y, Turanov, AA, Zhang, Y, Doblin, MA, Taylor, GT, Sanudo-Wilhelm, SA, Grigoriev, IV & Gladyshev, VN 2013, 'The central role of selenium in the biochemistry and ecology of the harmful pelagophyte, Aureococcus anophagefferens', The ISME Journal, vol. 7, no. 7, pp. 1333-1343.View/Download from: Publisher's site
The trace element selenium (Se) is required for the biosynthesis of selenocysteine (Sec), the 21st amino acid in the genetic code, but its role in the ecology of harmful algal blooms (HABs) is unknown. Here, we examined the role of Se in the biology and ecology of the harmful pelagophyte, Aureococcus anophagefferens, through cell culture, genomic analyses and ecosystem studies. This organism has the largest and the most diverse selenoproteome identified to date that consisted of at least 59 selenoproteins, including known eukaryotic selenoproteins, selenoproteins previously only detected in bacteria, and novel selenoproteins. The A. anophagefferens selenoproteome was dominated by the thioredoxin fold proteins and oxidoreductase functions were assigned to the majority of detected selenoproteins. Insertion of Sec in these proteins was supported by a unique Sec insertion sequence. Se was required for the growth of A. anophagefferens as cultures grew maximally at nanomolar Se concentrations. In a coastal ecosystem, dissolved Se concentrations were elevated before and after A. anophagefferens blooms, but were reduced by 495% during the peak of blooms to 0.05 nM. Consistent with this pattern, enrichment of seawater with selenite before and after a bloom did not affect the growth of A. anophagefferens, but enrichment during the peak of the bloom significantly increased population growth rates. These findings demonstrate that Se inventories, which can be anthropogenically enriched, can support proliferation of HABs, such as A. anophagefferens through its synthesis of a large arsenal of Se-dependent oxidoreductases that fine-tune cellular redox homeostasis.
Seymour, JR, Doblin, MA, Jeffries, TC, Brown, MV, Newton, K, Ralph, PJ, Baird, ME & Mitchell, JG 2012, 'Contrasting microbial assemblages in adjacent water masses associated with the East Australian Current', Environmental Microbiology Reports, vol. 4, pp. 548-555.View/Download from: Publisher's site
Different oceanographic provinces host discrete microbial assemblages that are adapted to local physicochemical conditions. We sequenced and compared the metagenomes of two microbial communities inhabiting adjacent water masses in the Tasman Sea, where the recent strengthening of the East Australian Current (EAC) has altered the ecology of coastal environments. Despite the comparable latitude of the samples, significant phylogenetic differences were apparent, including shifts in the relative frequency of matches to Cyanobacteria, Crenarchaeota and Euryarchaeota. Fine-scale variability in the structure of SAR11, Prochlorococcus and Synechococcus populations, with more matches to `warm-water ecotypes observed in the EAC, indicates the EAC may drive an intrusion of tropical microbes into temperate regions of the Tasman Sea. Furthermore, significant shifts in the relative importance of 17 metabolic categories indicate that the EAC prokaryotic community has different physiological properties than surrounding waters
This study examined the response of a coral holobiont to thermal stress when the bacterial community was treated with antibiotics. Colonies of Pocillopora damicornis were exposed to broad and narrow-spectrum antibiotics targeting coral-associated a and c-Proteobacteria. Corals were gradually heated from the control temperature of 26 to 31 C, and measurements were made of host, zooxanthellar and microbial condition. Antibiotics artificially reduced the abundance and activity of bacteria, but had minimal effect on zooxanthellae photosynthetic efficiency or host tissue protein content. Heated corals without antibiotics showed significant declines in FV/FM, typical of thermal stress. However, heated corals treated with antibiotics showed severe tissue loss in addition to a decline in FV/ FM. This study demonstrated that a disruption to the microbial consortium diminished the resilience of the holobiont. Corals exposed to antibiotics under control temperature did not bleach, suggesting that temperature may be an important factor influencing the activity, diversity and ecological function of the holobiont bacterial community.
Petrou, K, Kranz, SA, Doblin, MA & Ralph, PJ 2012, 'Photophysiological responses of Fragilariopsis cylindrus (Bacillariophyceae) to nitrogen depletion at two temperatures', Journal of Phycology, vol. 48, no. 1, pp. 127-136.View/Download from: Publisher's site
The photosynthetic efficiency and photoprotective capacity of the sea-ice diatom, Fragilariopsis cylindrus (Grunow) W. Krieg., grown in a matrix of nitrogen repletion and depletion at two different temperatures (-1 degrees C and +6 degrees C) was investigated. Temperature showed no significant effect on photosynthetic efficiency or photoprotection in F. cylindrus. Cultures under nitrogen depletion showed enhanced photoprotective capacity with an increase in nonphotochemical quenching (NPQ) when compared with nitrogen-replete cultures. This phenomenon was achieved at no apparent cost to the photosynthetic efficiency of PSII (FV/FM). Nitrogen depletion yielded a partially reduced electron transport chain in which maximum fluorescence (FM) could only be obtained by adding 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). reoxidation curves showed the presence of QB nonreducing PSII centers under nitrogen depletion. Fast induction curves (FICs) and electron transport rates (ETRs) revealed slowing of the electrons transferred from the primary (QA) to the secondary (QB) quinone electron acceptors of PSII. The data presented show that nitrogen depletion in F. cylindrus leads to the formation of QB nonreducing PSII centers within the photosystem. On a physiological level, the formation of QB nonreducing PSII centers in F. cylindrus provides the cell with protection against photoinhibition by facilitating the rapid induction of NPQ. This strategy provides an important ecological advantage, especially during the Antarctic spring, maintaining photosynthetic efficiency under high light and nutrient-limiting conditions.
Sinutok, S, Hill, R, Doblin, MA, Kuhl, M & Ralph, PJ 2012, 'Microenvironmental changes support evidence of photosynthesis and calcification inhibition in Halimeda under ocean acidification and warming', Coral Reefs, vol. 31, pp. 1201-1213.View/Download from: Publisher's site
The effects of elevated CO 2 and temperature on photosynthesis and calcification of two important calcifying reef algae (Halimedamacroloba and Halimeda cylindracea) were investigated with O 2 microsensors and chlorophyll a fluorometry through a combination of two pCO 2 (400 and 1,200 µatm) and two temperature treatments (28 and 32 °C) equivalent to the present and predicted conditions during the 2100 austral summer. Combined exposure to pCO 2 and elevated temperature impaired calcification and photosynthesis in the two Halimeda species due to changes in the microenvironment around the algal segments and a reduction in physiological performance. There were no significant changes in controls over the 5-week experiment, but there was a 50-70 % decrease in photochemical efficiency (maximum quantum yield), a 70-80 % decrease in O 2 production and a threefold reduction in calcification rate in the elevated CO 2 and high temperature treatment. Calcification in these species is closely coupled with photosynthesis, such that a decrease in photosynthetic efficiency leads to a decrease in calcification. Although pH seems to be the main factor affecting Halimeda species, heat stress also has an impact on their photosystem II photochemical efficiency. There was a strong combined effect of elevated CO 2 and temperature in both species, where exposure to elevated CO 2 or temperature alone decreased photosynthesis and calcification, but exposure to both elevated CO 2 and temperature caused a greater decline in photosynthesis and calcification than in each stress individually. Our study shows that ocean acidification and ocean warming are drivers of calcification and photosynthesis inhibition in Halimeda. Predicted climate change scenarios for 2100 would therefore severely affect the fitness of Halimeda, which can result in a strongly reduced production of carbonate sediments on coral reefs under such changed climate conditions.
Hallegraeff, GM, Blackburn, S, Doblin, MA & Bolch, C 2012, 'Global toxicology, ecophysiology and population relationships of the chainforming PST dinoflagellate Gymnodinium catenatum', Harmful Algae, vol. 14, pp. 130-143.View/Download from: Publisher's site
Increasing scientific awareness since the 1980s of the chain-forming dinoflagellate Gymnodinium catenatum has led to this species being reported with increased frequency in a globally increasing number of countries (23 at present). G. catenatum exhibits little molecular genetic variation in rDNA over its global range, in contrast to RAPD fingerprinting which points to high genetic variation within regional populations even between estuaries 50 km apart. All Australian and New Zealand strains possess a thymine nucleotide (T-gene) near the start of the 5.8S rRNA whereas all other global populations examined to date possess cytosine-nucleotide (C-gene), except for southern Japan which harbours both C-gene and T-gene strains. Together with cyst and plankton evidence this strongly suggests that both Australian and New Zealand populations have derived from southern Japan. Global dinoflagellate populations and cultures exhibit an extraordinary variation in PST profiles (STX and 21 analogues), but consistent regional patterns are evident with regard to the production of C1,2; C3,4; B1,2; and neoSTX analogues. PST profiles of cyst-derived cultures are deemed unrepresentative. Distinct ecophysiological differences exist between tropical (2132 °C) and warm-temperate ecotypes (1218 °C), but these appear unrelated to ITS genotypes and PST toxin phenotypes.
Doblin, MA, Petrou, K, Shelly, K, Westwood, K, van den Enden, R, Wright, S, Griffiths, B & Ralph, PJ 2011, 'Diel variation of chlorophyll-a fluorescence, phytoplankton pigments and productivity in the Sub-Antarctic and Polar Front Zones south of Tasmania, Australia', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 58, no. 21-22, pp. 2189-2199.View/Download from: Publisher's site
Marine primary production is a fundamental measure of the oceanâs capacity to convert carbon dioxide to particulate organic carbon for the marine foodweb, and as such is an essential variable used in ecosystem and biogeochemical models to assess trophic dynamics and carbon cycling. The Sub-Antarctic Zone (SAZ) is a major sink for atmospheric carbon and exhibits large gradients in ocean conditions on both temporal and spatial scales. In this dynamic system, an understanding of small-scale temporal changes is critical for modelling primary production at larger scales. Thus, we investigated diel effects on maximum quantum yield of PSII (FV/FM), photosynthetic pigment pools and primary productivity in the western (Diel 1) and eastern SAZ region (Diel 3) south of Tasmania, Australia, and compared this to a station at the polar front (Diel 2). Phytoplankton in the eastern SAZ had the greatest diel response, with cells showing decreased FV/FM and increased biosynthesis and transformation of xanthophyll and other photoprotective pigments during the day, but only in the surface waters (0 and 10m). Diel responses diminished by 30 m. Cells in the western SAZ had similar responses across the depths sampled, increasing their FV/FM during the night and increasing their xanthophyll pigment content during the day. Phytoplankton at the polar front (Diel 2) showed intermediate diel-related variations in photophysiology, with xanthophyll conversion and increases in photoprotective pigments during the day but constant FV/FM.
Earp, AA, Hanson, CE, Ralph, PJ, Brando, VE, Allen, S, Baird, ME, Clementson, L, Daniel, P, Dekker, AG, Fearns, PR, Parslow, JS, Strutton, PG, Thompson, P, Underwood, M, Weeks, S & Doblin, MA 2011, 'Review of fluorescent standards for calibration of in situ fluorometers: Recommendations applied in coastal and ocean observing programs', Optics Express, vol. 19, no. 27, pp. 26768-26782.View/Download from: Publisher's site
Fluorometers are widely used in ecosystem observing to monitor fluorescence signals from organic compounds, as well as to infer geophysical parameters such as chlorophyll or CDOM concentration, but measurements are susceptible to variation caused by biofouling, instrument design, sensor drift, operating environment, and calibration rigor. To collect high quality data, such sensors need frequent checking and regular calibration. In this study, a wide variety of both liquid and solid fluorescent materials were trialed to assess their suitability as reference standards for performance assessment of in situ fluorometers. Criteria used to evaluate the standards included the spectral excitation/emission responses of the materials relative to fluorescence sensors and to targeted ocean properties, the linearity of the fluorometerâs optical response with increasing concentration, stability and consistency, availability and ease of use, as well as cost. Findings are summarized as a series of recommended reference standards for sensors deployed on stationary and mobile platforms, to suit a variety of in situ coastal to ocean sensor configurations. Repeated determinations of chlorophyll scale factor using the recommended liquid standard, Fluorescein, achieved an accuracy of 2.5%. Repeated measurements with the recommended solid standard, Plexiglas Satinice® plum 4H01 DC (polymethylmethacrylate), over an 18 day period varied from the mean value by 1.0% for chlorophyll sensors and 3.3% for CDOM sensors.
Petrou, K, Doblin, MA & Ralph, PJ 2011, 'Heterogeneity in the photoprotective capacity of three Antarctic diatoms during short-term changes in salinity and temperature', Marine Biology, vol. 158, no. 5, pp. 1029-1041.View/Download from: Publisher's site
The Antarctic marine ecosystem changes seasonally, forming a temporal continuum of specialised niche habitats including open ocean, sea ice and meltwater environments. The ability for phytoplankton to acclimate rapidly to the changed conditions of these environments depends on the speciesâ physiology and photosynthetic plasticity and may ultimately determine their long-term ecological niche adaptation. This study investigated the photophysiological plasticity and rapid acclimation response of three Antarctic diatomsâFragilariopsis cylindrus, Pseudo-nitzschia subcurvata and Chaetoceros sp.âto a selected range of temperatures and salinities representative of the sea ice, meltwater and pelagic habitats in the Antarctic. Fragilariopsis cylindrus displayed physiological traits typical of adaptation to the sea ice environment. Equally, this species showed photosynthetic plasticity, acclimating to the range of environmental conditions, explaining the prevalence of this species in all Antarctic habitats. Pseudo-nitzschia subcurvata displayed a preference for the meltwater environment, but unlike F. cylindrus, photoprotective capacity was low and regulated via changes in PSII antenna size. Chaetoceros sp. had high plasticity in non-photochemical quenching, suggesting adaptation to variable light conditions experienced in the wind-mixed pelagic environment. While only capturing short-term responses, this study highlights the diversity in photoprotective capacity that exists amongst three dominant Antarctic diatom species and provides insight into links between ecological niche adaptation and speciesâ distribution
Petrou, K, Hassler, CS, Doblin, MA, Shelly, K, Schoemann, V, van den Enden, R, Wright, S & Ralph, PJ 2011, 'Iron-limitation and high light stress on phytoplankton populations from the Australian Sub-Antarctic Zone (SAZ)', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 58, no. 21-22, pp. 2200-2211.View/Download from: Publisher's site
The high nutrient low chlorophyll (HNLC) surface waters of the Southern Ocean are characterised by high concentrations of nitrate and phosphate, low concentrations of dissolved iron and deep vertical mixing. Future climate scenarios predict increased sur
Petrou, K, Hill, R, Doblin, MA, McMinn, A, Johnson, R, Wright, SW & Ralph, PJ 2011, 'Photoprotection of sea-ice microalgal communities from the east Antarctic pack ice', Journal of Phycology, vol. 47, no. 1, pp. 77-86.View/Download from: Publisher's site
All photosynthetic organisms endeavor to balance energy supply with demand. For sea-ice diatoms, as with all marine photoautotrophs, light is the most important factor for determining growth and carbonfixation rates. Light varies from extremely low to often relatively high irradiances within the sea-ice environment, meaning that sea-ice algae require moderate physiological plasticity that is necessary for rapid light acclimation and photoprotection. This study investigated photoprotective mechanisms employed by bottom Antarctic sea-ice algae in response to relatively high irradiances to understand how they acclimate to the environmental conditions presented during early spring, as the light climate begins to intensify and snow and sea-ice thinning commences.
Sinutok, S, Hill, R, Doblin, MA, Wuhrer, R & Ralph, PJ 2011, 'Warmer more acidic conditions cause decreased productivity and calcification in subtropical coral reef sediment-dwelling calcifiers', Limnology and Oceanography, vol. 56, no. 4, pp. 1200-1212.View/Download from: Publisher's site
The effects of elevated CO(2) and temperature on photosynthesis and calcification in the calcifying algae Halimeda macroloba and Halimeda cylindracea and the symbiont-bearing benthic foraminifera Marginopora vertebralis were investigated through exposure to a combination of four temperatures (28 degrees C, 30 degrees C, 32 degrees C, and 34 degrees C) and four CO(2) levels (39, 61, 101, and 203 Pa; pH 8.1, 7.9, 7.7, and 7.4, respectively). Elevated CO(2) caused a profound decline in photosynthetic efficiency (F(V) : F(M)), calcification, and growth in all species. After five weeks at 34 degrees C under all CO(2) levels, all species died. Chlorophyll (Chl) a and b concentration in Halimeda spp. significantly decreased in 203 Pa, 32 degrees C and 34 degrees C treatments, but Chl a and Chl c(2) concentration in M. vertebralis was not affected by temperature alone, with significant declines in the 61, 101, and 203 Pa treatments at 28 degrees C. Significant decreases in F(V) : F(M) in all species were found after 5 weeks of exposure to elevated CO(2) (203 Pa in all temperature treatments) and temperature (32 degrees C and 34 degrees C in all pH treatments). The rate of oxygen production declined at 61, 101, and 203 Pa in all temperature treatments for all species. The elevated CO(2) and temperature treatments greatly reduced calcification (growth and crystal size) in M. vertebralis and, to a lesser extent, in Halimeda spp. These findings indicate that 32 degrees C and 101 Pa CO(2), are the upper limits for survival of these species on Heron Island reef, and we conclude that these species will be highly vulnerable to the predicted future climate change scenarios of elevated temperature and ocean acidification.
Baird, ME, Suthers, I, Griffin, DA, Hollings, B, Pattiaratchi, CB, Everett, J, Roughan, M, Oubelkheir, K & Doblin, MA 2011, 'The effect of surface flooding on the physical-biogeochemical dynamics of a warm-core eddy off southeast Australia', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 58, no. 5, pp. 592-605.View/Download from: Publisher's site
Warm core eddies (WCEs) formed from the East Australian Current (EAC) play an important role in the heat, mass and biogeochemical budgets of the western Tasman Sea. The development and separation of an EAC WCE during July-December 2008 was observed using remotely-sensed temperature, ocean colour and sea-level elevation, three Argo floats, a shipboard CTD, a shelf mooring array and a 15-day deployment of a Slocum glider.
Hassler, CS, Djajadikarta, J, Doblin, MA, Everett, J & Thompson, P 2011, 'Characterisation Of Water Masses And Phytoplankton Nutrient Limitation In The East Australian Current Separation Zone During Spring 2008', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 58, no. 5, pp. 664-677.View/Download from: Publisher's site
This study focuses on the comparison of oceanic and coastal cold-core eddies with inner-shelf and East Australian Current (EAC) waters at the time of the spring bloom (October 2008).
Thompson, P, Bonham, P, Waite, A, Clementson, L, Cherukuru, N, Hassler, CS & Doblin, MA 2011, 'Contrasting Oceanographic Conditions And Phytoplankton Communities On The East And West Coasts Of Australia', Deep-Sea Research Part Ii-Topical Studies In Oceanography, vol. 58, no. 5, pp. 645-663.View/Download from: Publisher's site
The composition and dynamics of the phytoplankton communities and hydrographic factors that control them are described for eastern and western Australia with a focus on the Eastern Australian Current (EAC) and Leeuwin Current (LC) between 27.5 degrees and 34.51S latitude.
Petrou, K, Hill, R, Brown, CM, Campbell, DA, Doblin, MA & Ralph, PJ 2010, 'Rapid photoprotection in sea-ice diatoms from the East Antarctic pack ice', Limnology and Oceanography, vol. 55, no. 3, pp. 1400-1407.View/Download from: Publisher's site
Photoinhibition and D1 protein re-synthesis were investigated in bottom-dwelling sea-ice microalgal communities from the East Antarctic pack ice during early spring. Bottom-dwelling sea-ice microalgal communities were dominated by diatoms that exhibited rapid photoprotection when exposed to a range of different light levels (10 µmol photons m-2 s-1, 50 µmol photons m-2 s-1, 100 µmol photons m-2 s-1, and 200 µmol photons m-2 s-1). Photosynthetic capacity of photosystem II (PSII) dropped significantly over 3 h under 200 µmol photons m-2 s-1, but largely recovered when placed in a low-light environment (10 µmol photons m-2 s-1) for an additional 3 h. PSII repair rates increased with increasing irradiance, and the D1-protein pool remained steady even under high light (200 µmol photons m-2 s-1). Sea-ice diatoms showed a low intrinsic susceptibility to photoinactivation of PSII across all the light treatments, and a strong and irradiance-dependent induction of nonphotochemical quenching, which did not depend upon chloroplast protein synthesis, was also seen. These highly plastic organisms, once thought to be adapted to shade, are in fact well equipped to withstand rapid and relatively large changes in light at low temperatures with minimal long-term effect on their photosynthetic machinery.
Doblin, MA, Murphy, KR & Ruiz, GM 2010, 'Thresholds for tracing ships' ballast water:an Australian case study', Marine Ecology Progress Series, vol. 408, pp. 19-32.View/Download from: Publisher's site
To limit the spread of non-indigenous marine species, ships can be legally required to conduct ballast water exchange (BWE) prior to discharging ballast water. It has been proposed to verify BWE by measuring concentrations of coastal tracers in ballast tanks, which should track their removal. Using 3 Australian ports as case studies (Port Botany, Port Curtis and Port Phillip Bay), each representing a different BWE verification difficulty level, the spatial and temporal variability of chromophoric dissolved organic matter (CDOM) and 3 trace elements (manganese [Mn], barium [Ba] and phosphorus [P]), were measured to assess their utility as tracers of coastal (unexchanged) ballast water. CDOM fluorescence at Î»ex/Î»em = 320/414 nm (C2*) and 370/494 nm (C3*) and Mn concentrations were significantly higher in ports than in the adjacent Tasman Sea, except near port entrances and at a few sites in Port Botany. Ba concentrations demonstrated the least power to discriminate coastal sources, but P easily discriminated water from mesotrophic Port Phillip Bay. In general, tracers showed greater variation between and within ports, rather than between seasons. Conservative BWE thresholds were calculated to be 1.6 quinine sulphate equivalents for C2*, 0.9 quinine sulphate equivalents for C3*, 1.4 Î¼g lâ1 for Mn and 6.9 Î¼g lâ1 for Ba. Overall, these thresholds would allow water sourced from eastern Australian ports to be identified as coastal at 92%, 69% and 74% of sites examined using C3*, Mn and Ba, respectively, requiring 71 Â± 26%, 54 Â± 40% and 59 Â± 38% replacement with mid-ocean water to be within ocean baseline concentration ranges.
Fahnenstiel, G, Hong, Y, Millie, D, Doblin, MA, Johengen, T & Reid, D 2009, 'Marine dinoflagellate cysts in the ballast tank sediments of ships entering the Laurentian Great Lakes', Verhandlungen Internationale Verein Limnology, vol. 30, no. 7, pp. 1035-1038.
Gribben, PE, Wright, JT, O'Connor, W, Doblin, MA, Eyre, B & Steinberg, P 2009, 'Reduced performance of native infauna following recruitment to a habitat-forming invasive marine alga', Oecologia, vol. 158, no. 4, pp. 733-745.View/Download from: Publisher's site
Despite well-documented negative impacts of invasive species on native biota, evidence for the facilitation of native organisms, particularly by habitat-forming invasive species, is increasing. However, most of these studies are conducted at the population or community level, and we know little about the individual fitness consequences of recruitment to habitat-forming invasive species and, consequently, whether recruitment to these habitats is adaptive. We determined the consequences of recruitment to the invasive green alga Caulerpa taxifolia on the native soft-sediment bivalve Anadara trapezia and nearby unvegetated sediment. Initially, we documented the growth and survivorship of A. trapezia following a natural recruitment event, to which recruitment to C. taxifolia was very high. After 12 months, few clams remained in either habitat, and those that remained showed little growth. Experimental manipulations of recruits demonstrated that all performance measures (survivorship, growth and condition) were significantly reduced in C. taxifolia sediments compared to unvegetated sediments. Exploration of potential mechanisms responsible for the reduced performance in C. taxifolia sediments showed that water flow and water column dissolved oxygen (DO) were significantly reduced under the canopy of C. taxifolia and that sediment anoxia was significantly higher and sediment sulphides greater in C. taxifolia sediments. However, phytoplankton abundance (an indicator of food supply) was significantly higher in C. taxifolia sediments than in unvegetated ones. Our results demonstrate that recruitment of native species to habitat-forming invasive species can reduce growth, condition and survivorship and that studies conducted at the community level may lead to erroneous conclusions about the impacts of invaders and should include studies on life-history traits, particularly juveniles.
Thompson, PA, Baird, ME, Ingleton, T & Doblin, MA 2009, 'Long-term changes in temperate Australian coastal waters: implications for phytoplankton', Marine Ecology Progress Series, vol. 394, pp. 1-19.View/Download from: Publisher's site
A ~60 yr physical and chemical data set from 4 coastal stations around Australia plus remotely sensed SeaWiFS and phytoplankton taxonomic data were used to evaluate the temporal and spatial variation in phytoplankton ecology. The most consistent trend observed at all stations was a long-term increase in surface salinity of ~0.003 ± 0.0008 psu yr1. All stations showed positive trends in temperature, with the fastest surface warming (0.0202°C yr1 over 60 yr) in the western Tasman Sea. Long-term trends in warming and stratification were more evident in some months and were not well characterized by annual averages. There was no general pattern of increasing stratification (0 to 50 m); only some stations and a few months showed significant changes. Long-term trends in surface nitrate and phosphate concentrations were either not significant (3 instances) or positive (5 instances) and were up to 6.1 nM phosphate yr1. A pronounced decline in silicate was evident at the 3 east coast stations, with concentrations falling by as much as 58 nM yr1 over the last ~30 yr. The western Tasman Sea experienced a ~50% decline in the growth rate and biomass of the spring bloom from 1997 to 2007, while other sites showed significant temporal variability in chlorophyll a that was associated with the Southern Oscillation Index (SOI). Diatoms tended to dominate the microplankton, especially during periods of low stratification. In conclusion, the physical, chemical and biological properties of Australian temperate waters have changed considerably over the last 60 yr in response to variation in the SOI and the strengthening East Australian Current.
Gilbert, PM, Azanza, R, Burford, MA, Furuya, K, Abal, E, Al-Azri, A, Al-Yamani, F, Andersen, P, Anderson, DM, Beardall, J, Berg, GM, Brand, L, Bronk, D, Brookes, J, Burkholder, JM, Cembella, A, Cochlan, WP, Collier, JL, Collos, Y, Diaz, R, Doblin, MA, Drennen, T, Dyhrman, S, Fukuyo, Y, Furnas, M, Galloway, J, Graneli, E, Ha, D, Hallegraeff, GM, Harrison, J, Harrison, P, Heil, CA, Heimann, K, Howarth, R, Jauzein, M, Kana, AA, Kana, TM, Kim, H, Kudela, R, Legrand, C, Mallin, M, Mulholland, M, Murray, SA, O'Neil, J, Pitcher, G, Qi, Y, Rabalais, N, Raine, R, Seitzinger, S, Salomon, PS, Solomon, C, Stoecker, DK, Usup, G, Wilson, J, Yin, K, Zhou, M & Zhu, M 2008, 'Ocean urea fertilization for carbon credits poses high ecological risks', Marine Pollution Bulletin, vol. 56, no. 6, pp. 1049-1056.View/Download from: Publisher's site
The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed. Â© 2008 Elsevier Ltd. All rights reserved.
Petrou, K, Doblin, MA, Smith, RA, Ralph, PJ, Shelly, K & Beardall, J 2008, 'State transitions and nonphotochemical quenching during a nutrient-induced fluorescence transient in phosphorus-starved Dunaliella tertiolecta', Journal of Phycology, vol. 44, pp. 1204-1211.View/Download from: Publisher's site
Assessments of nutrient-limitation in microalgae using chl a fluorescence have revealed that nitrogen and phosphorus depletion can be detected as a change in chl a fluorescence signal when nutrient-starved algae are resupplied with the limiting nutrient.
Demir, E, Coyne, K, Doblin, MA, Handy, S & Hutchins, DA 2008, 'Assessment of microzooplankton grazing on Heterosigma akashiwo using a species-specific approach combining quantitative real-time PCR (QPCR) and dilution methods', Microbial Ecology, vol. 55, no. 4, pp. 583-594.View/Download from: Publisher's site
Delaware's Inland Bays (DIB) are subject to numerous mixed blooms of harmful raphidophytes each year, and Heterosigma akashiwo is one of the consistently occurring species. Often, Chattonella subsalsa, C. cf. verruculosa, and Fibrocapsa japonica co-occur
Demir, E, Coyne, KJ, Doblin, MA, Handy, SM & Hutchins, DA 2008, 'Assessment of microzooplankton grazing on Heterosigma akashiwo using a species-specific approach combining quantitative real-time PCR (QPCR) and dilution methods (vol 55, pg 583, 2008)', MICROBIAL ECOLOGY, vol. 55, no. 4, pp. 581-582.View/Download from: Publisher's site
Ralph, PJ, Durako, M, Enriquez, S, Collier, C & Doblin, MA 2007, 'Impact of light limitation on seagrasses', Journal of Experimental Marine Biology and Ecology, vol. 350, no. 1-2, pp. 176-193.View/Download from: Publisher's site
Seagrass distribution is controlled by light availability, especially at the deepest edge of the meadow. Light attenuation due to both natural and anthropogenically-driven processes leads to reduced photosynthesis. Adaptation allows seagrasses to exist under these sub-optimal conditions. Understanding the minimum quantum requirements for growth (MQR) is revealed when light conditions are insufficient to maintain a positive carbon balance, leading to a decline in seagrass growth and distribution. Respiratory demands of photosynthetic and non-photosynthetic tissues strongly influence the carbon balance, as do resource allocations between above- and below-ground biomass. Seagrass light acclimation occurs on varying temporal scales, as well as across spatial scales, from the position along a single leaf blade to within the canopy and finally across the meadow. Leaf absorptance is regulated by factors such as pigment content, morphology and physical properties. Chlorophyll content and morphological characteristics of leaves such as leaf thickness change at the deepest edge. We present a series of conceptual models describing the factors driving the light climate and seagrass responses under current and future conditions, with special attention on the deepest edge of the meadow.
Doblin, MA, Coyne, K, Rinta-kanto, J, Wilhelm, S & Dobbs, FC 2007, 'Dynamics and short-term survival of toxic cyanobacteria species in ballast water from NOBOB vessels transiting the Great Lakes - implications for HAB invasions', Harmful Algae, vol. 6, no. 4, pp. 519-530.View/Download from: Publisher's site
We measured the presence, viability and potential toxicity of cyanobacteria in ships' ballast tanks during three domestic voyages through the North American Great Lakes. Using molecular methods, the toxin-producing forms of Microcystis and Anabaena were monitored in ballast water after ships' ballast tanks were filled at their first port of call, and at subsequent ports as ships transited the Great Lakes. Microcystis weas detected in ballast water at intermidiate and final ports of call in all three experiemnts, but the presence of Anabaena was more variable, suggesting low abundance or patchy distribution in ballast tanks. Both species were detected in ballast water up to 11 days old. Detection of the mucrocystin synthetase gene, mcyE, in ballst tanks indicated entrained cells were capable of producing mycrocystin, and further analyses of RNA indicated the toxin was being expressed by Microcystis, even after 11 days in dark transit. These data demonstrate within-basin transport and delivery of planktonic harmful algal bllom (HAB) species to distant ports in the world's largest freshwater resevoir, with potential implications for drinking water quality. These implications are discussed with respect to management of microbial invasions and the fate of introduced phytoplankton in their receiving environment.
Drake, L, Doblin, MA & Dobbs, FC 2007, 'Potential microbial bioinvasions via ships' ballast water, sediment, and biofilm', Marine Pollution Bulletin, vol. 55, no. 7-9, pp. 333-341.View/Download from: Publisher's site
A prominent vector of aquatic invasive species to coastal regions is the discharge of water, sediments and biofilm from ships' ballast-water tanks. During eight years of studying ships arriving to the lower Chesapeake Bay, we developed an undertsnading of th mechanisms by which invasive microorganisms might arrive to the region via ships. Within a given ship, habitats included ballast water, unpumpable water and sediment (collectively known as residuals) and biofilms formed on internal surfaces of ballast-water tanks. We sampled 69 vessels arriving from foreign and domestic ports, largely from Western Europe and Mediterranean region and the US East and Gulf coasts. All habitats contained bacteria and viruses. By extrapolating the measured concentration of a microbial metric to the estimated volume of ballast water, biofilm or residual sediment and water within an average vessel, we calculated the potential total number of microorganisms contained by each habitat, thus creating a hierarchy of risk of delivery. The estimated concentration of microorganisms was greatest in ballast water >> sediment and water residuals >> biofilms. From these results, it is clear microorganisms may be transported within ships ina varierty of ways. Using temperature tolerence as a measure of survivability and the temperature difference between ballst-water samples and the water into which the ballast water was discharged, we estimated 56% of microorganisms could survive in the lower Bay. Extrapolated delivery and survival of microorganisms to thePort of Hampton Roads in lower Chesapeake Bay shows on the order of 10 20 microorganisms are discharged annually into the region.
Doblin, MA & Dobbs, FC 2006, 'Setting a size-exclusion limit to remove toxic dinoflagellate cysts from ships ballast water', Marine Pollution Bulletin, vol. 52, no. 3, pp. 259-263.View/Download from: Publisher's site
Dinoflagellate cysts are well-recognized biological constituents of ships ballast tanks. They are present in ballast water, sediments and residual water in drained tanks, and in biofilms formed on interior tank Surfaces. Therefore, cysts have the potenti
Doblin, MA, Baines, SB, Cutter, LS & Cutter, GA 2006, 'Sources and biogeochemical cycling of particulate selenium in the San Francisco Bay estuary', Estuarine Coastal And Shelf Science, vol. 67, no. 4, pp. 681-694.View/Download from: Publisher's site
As part of a study of estuarine selenium cycling, we measured the concentration, chemical form (speciation), and distribution of particulate selenium under various river flow conditions in the North San Francisco Bay (from the Golden Gate to the Sacramen
Doblin, MA, Thompson, P, Revill, A, Butler, E, Blackburn, S & Hallegraeff, GM 2006, 'Vertical migration of the toxic dinoflagellate Gymnodinium catenatum under different concentrations of nutrients and humic substances in culture', Harmful algae, vol. 5, no. 6, pp. 665-677.View/Download from: Publisher's site
Vertical migration behaviour by the chainforming dinoflagellate Gymnodinium catenatum Graham was investigated using vertically-stratified laboratory columns. Under surface nutrient-deplete conditions, with nutrients added only at depth, 100% of cells underwent vertical migration (VM), starting downwards migration 3 h before the end of the light period and beginning upwards migration 3 h before the start of the light period. Cells in nutrient-replete columns showed no VM, but they were more dispersed in the upper layer during the dark compared to the light period. When surface layers (S) were nitrate-deplete (-N) and enriched with humic substances (H) contained in Huon River water and bottom waters (B) were nutrient replete (R) (SH-NBR), the pattern of VM was altered-50% of cells underwent migration and 50% remained at the pycnocline. In columns with nitrate-replete and humic-enriched surface layers (SHRBR), Most cells underwent VM, while 30% remained at the surface. Cells in SH-NBR columns showed increased N quotas and intra-cellular nitrate concentrations after 4 days, indicating nitrate uptake by G. catenatum in bottom layers. The concomitant increase in particulate organic nitrogen (PON) with the decrease in external nitrate concentrations in bottom layers provide convincing evidence that VM by G. catenatum facilitates nutrient retrieval at depth. However, addition of humic substances (a potential source of organic nitrogen) to surface layers did not ameliorate G. catenatum N depletion sufficiently to preclude the need for NO3- uptake at depth. Furthermore, there was no detectable pattern of increasing carbon (C) quota during the day (photosynthate accumulation) or increasing N quota during the night (nitrate assimilation).
Handy, SM, Coyne, KJ, Portune, KJ, Demir, E, Doblin, MA, Hare, CE, Cary, SC & Hutchins, DA 2006, 'Erratum: Evaluating vertical migration behavior of harmful raphidophytes in the Delaware Inland Bays utilizing quantitative real-time PCR (Aquatic Microbial Ecology (2005) 40, (121-132))', Aquatic Microbial Ecology, vol. 42, no. 3, p. 311.
Willhelm, S, Carberry, M, Eldridge, M, Poorvin, L, Saxton, M & Doblin, MA 2006, 'Marine and Freshwater Cyanophages in a Laurentian Great Lake: Evidence from Infectivity Assays and Molecular Anayses of g20 genes', Applied and Environmental Microbiology, vol. 72, no. 7, pp. 4957-4963.View/Download from: Publisher's site
While it is well established that viruses play an important role in the sturcture of marine microbisal food webs, few studies have directly addresed their role in large lake systems. As part of an ongoing study of the microbial acology of Lake Erie, we have examined the distribution and diversity of viruses in this system. One surprising result has bee the pervasive distribution of cyanophages that infect the marine cyanobacterial isolate Synechococcus sp. strain WH7803. Viruses that typically infect this cyanobacterium wre identified throughout the western basin of Lake Erie, as well as in locations within the central and eastern basins. Analyses of the gene encoding the g20 viral capsid assembly protein (a conservative phylogenetic marker for the cyanophage) indicate that these viruses as well as amplicons from natural populations and the ballast of commercial ships are related to marine cyanophages but in some cases form a unique clade, leaving questions concerning the native hosts of these viruses. The results suggest that cyanophages may be as important in freshwater systems as they are known to be in marine systems.
Coyne, K, Handy, S, Demir, E, Whereat, E, Hutchins, DA, Portune, K, Doblin, MA & Cary, S 2005, 'Improved quantitative real-time PCR assays for enumeration of harmful algal species in field samples using an exogenous DNA reference standard', Limnology and Oceanography: Methods, vol. 3, pp. 381-391.
Quantitative real-time PCR (QPCR) is a powerful and sensitive method for quantitative detection of microorganisms. Application of this methodology for enumeration of harmful algal bloom (HAB) species has the potential to revolutionize our approach to HAB research, making it possible to identify correlations between cell abundances and factors that regulate bloom dynamics. Its application to ecological studies, however, has produced mixed results. QPCR assays typically rely of the generation of standard curves from plasmids or laboratory cultures that may be unrealistic whencompared to amplification of DNA extracted from field samples. In addition, existing methods often fail to incorporate controls to assess variability in extraction and amplification efficiencies,or include controls that are sequence-specific and preclude the investigation of multiple species. Here, we describe the development and rigorous analysis of QPCR awways for two HAB species, Chattonella subsala and Heterosigma akashiwo, in which we introduce a known concentration of exogenous DNA plasmid into the extraction buffer as a refernce standard. Since the target DNA is extracted in the presence of the reference standard, inherent variability in extraction and amplification efficiencies affect both target and standard equally. Furthermore, the reference standard is application to QPCR analysis of any microbial species. Using environmental bloom samples as calibrators, we evaluated the accuracy of the comparative Ct method for enumeration of target species in several field smaples, Out investigation demonstrates that the comparative Ct method with an exogenous DNA reference standard provides both accurate and reproducible quantification of HAB species in environmental samples.
Drake, L, Meyer, A, Forsberg, R, Baier, R, Doblin, MA, Heinemann, SH, Johnson, W, Koch, M, Roblee, P & Dobbs, FC 2005, 'Potential invasion of microorganisms and pathogens via 'interior hull fouling': biofilms inside ballast water tanks', Biological Invasions, vol. 7, pp. 969-982.View/Download from: Publisher's site
Surfaces submerged in an aquatic milieu are covered to some degree with biofilms - organic matrices that can contain bacteria, microalgae, and protozoans, sometimes including disease-causing forms. One unquantified risk of aquatic biological invatsions is the potential for biofilms within ships' ballast water tanks to harbour pathogens, and, in tuen, seed othe waters. To begin to evaluate this vector, we collected biofilm samples fromtanks' surfaces and deployed controlled-surface sampling units within tanks. We then measured a variety of microbial metrics within the biofilms to test the hypotheses that pathogens are present in biofilms and that biofilms have higher microbial densities compared to ballst water. Field experiments and sampling of coastwise and oceangoing ships arriving at ports in Chesapeake Bay and the North American Great Lakes showed the presence of abundant microorganisms, including pathogens, in biofilms. These results suggest that ballast-tank biofilms represent an additional risk of microbial invasion, provided they release cells into the water or they are sloughed off during normal ballasting operations.
Handy, S, Coyne, K, Portune, K, Demir, E, Doblin, MA, Hare, CE, Cary, S & Hutchins, DA 2005, 'Evaluating vertical migration behaviour of harmful raphidophytes in the Delaware Inland Bays utilizing quantitative real-time PCR', Aquatic Microbial Ecology, vol. 40, pp. 121-132.View/Download from: Publisher's site
Mixed blooms of 4 species of harmful raphidophytes (Chattonella cf. verruculosa, Chattonella subsalsa, Heterosigma akashiwo, and Fibrocapsa japonica) occur in the shallow (1 ti 2m) Delaware Inland Bays (DIB), USA. Raphidophytes vertically migrate in other deeper water ecosystems to utilise deep nutrient stocks at night, and thus obtain an advantage over non-migrating algae.Anoxic DIB sediments release high levels of bioavailable phosphate, which could potentially be used by vertically migrating flagellates. This study aimed to characterise and understamd the migration oatterns of DIB raphidiphytes, and determine whether benthic phosphate fluxes could provide the cells with P. We demonstrated vertical migration of isolated DIB raphidophyte cultures in the laboratory, where differences inthe response of C. subsalsa and H. akashiwo to light:dark period manipulations suggested possible diffeerneces in external versus endogenous regulation of migration behaviour in the 2 species. Natural blooms in the filed (enclosed in a mesocosm system) also exhibited patterns of diel vertical distributions of each species. Our data suggested that these 2 photoautotrophic species spend daylight hours near the surface and are found directly on the sediment surface at night. However, diel changes in particulate C:P ratios did not support the hypothesis that there is preferential uptake of sedimentary phosphate at night. Our results also suggested that the migration behaviour may have important implications for designing sampling strategies for monitoring programs. QPCR has a number of decisive advantages over traditional microscopic counting methods, making this a poweful tool for fine spatial temporal scale detection and enum,eration of vertically migrating harmful algal species.
Aridgides, LJ, Doblin, MA, Berke, T, Dobbs, FC, Matson, DO & Drake, L 2004, 'Multiplex PCR allows simultaneous detection of pathogens in ships' ballast water', Marine Pollution Bulletin, vol. 48, no. 11-12, pp. 1096-1101.View/Download from: Publisher's site
There is enormous potential for global transfer of microorganisms, including pathogens, in ships' ballast water. We contend that a major advancement in the study of ballast-water microorganisms in particular, and of aquatic pathogens in general, will be expedited sample analysis, such as provided by the elegant technology of DNA microarrays. In order to use DNA microarrays, however, one must establish the appropriate conditions to bind target sequences in samples to multiple probes on the microarrays. We conducted proof-of-concept experiments to optimize simultaneous detection of multiple microorganisms using polymerase chain reaction (PCR) and Southern hybridization. We chose three target organisms, all potentially found in ballast water: a calicivirus, the bacterium Vibrio cholerae, and the photosynthetic protist Aureococcus anophagefferens. Here, we show simultaneous detection of multiple pathogens is possible, a result supporting the promising future use of microarrays for simultaneous detection of pathogens in ballast water.
Baines, SB, Fisher, NK, Doblin, MA, Cutter, GA, Cutter, LS & Cole, B 2004, 'Light dependence of selenium uptake by phytoplankton and implications for predicting selenium incorporation into food webs', Limnology and Oceanography, vol. 49, no. 2, pp. 566-578.View/Download from: Publisher's site
The potentially toxic element selenium is first concentrated from solution to a large but highly variable degree by algae and bacteria before being passed on to consumers. The large loads of abiotic and detrital suspended particles often present in rivers and estuaries may obscure spatial and temporal patterns in Se concentrations at the base of the food web. We used radiotracers to estimate uptake of both selenite (Se(IV)) and C by intact plankton communities at two sites in the Sacramento/San Joaquin River Delta. Our goals were to determine (1) whether C and Se(IV) uptake were coupled, (2) the role of bacteria in Se(IV) uptake, and (3) the Se: C uptake ratio of newly produced organic material. Se(IV) uptake, like C uptake, was strongly related to irradiance. The shapes of both relationships were very similar except that at least 42-56% of Se(IV) uptake occurred in the dark, whereas C uptake in the dark was negligible. Of this dark Se(IV) uptake, 34-67% occurred in the 0.2-1.0-mum size fraction, indicating significant uptake by bacteria. In addition to dark uptake, total Se(IV) uptake consisted of a light-driven component that was in fixed proportion to C uptake. Our estimates of daily areal Se(IV): C uptake ratios agreed very well with particulate Se: C measured at a site dominated by phytoplankton biomass. Estimates of bacterial Se: C were 2.4-13 times higher than for the phytoplankton, suggesting that bacteriovores may be exposed to higher dietary Se concentrations than herbivores.
Doblin, MA, Popels, LC, Coyne, K, Hutchins, DA, Cary, S & Dobbs, FC 2004, 'Transport of the harmful bloom alga Aureococcus anophagefferens by oceangoing ships and coastal boats', Applied and Environmental Microbiology, vol. 70, no. 11, pp. 6495-6500.View/Download from: Publisher's site
It is well established that cyst-forming phytoplankton species are transported in ships' ballast tanks. However, there is increasing evidence that other phytoplankton species which do not encyst are also capable of surviving ballast transit. These species have alternative modes of nutrition (hetero- or mixotrophy) and/or are able to survive long-term darkness. In our studies of no-ballast-on-board vessels arriving in the Great Lakes, we tested for the presence of the harmful algal bloom species Aureococcus anophagefferens (brown tide) in residual (i.e., unpumpable) ballast water using methods based on the PCR. During 2001, the brown tide organism was detected in 7 of 18 ballast water tanks in commercial ships following transit from foreign ports. Furthermore, it was detected after 10 days of ballast tank confinement during a vessel transit in the Great Lakes, a significant result given the large disparity between the salinity tolerance for active growth of Aureococcus (>22 ppt) and the low salinity of the residual ballast water (similar to2 ppt). We also investigated the potential for smaller, recreational vessels to transport and distribute Aureococcus. During the summer of 2002, 11 trailered boats from the inland bays of Delaware and coastal bays of Maryland were sampled. Brown tide was detected in the bilge water in the bottoms of eight boats, as well as in one live-well sample. Commercial ships and small recreational boats are therefore implicated as potential vectors for long-distance transport and local-scale dispersal of Aureococcus.
Stewart, AR, Luoma, SN, Schlekat, CE, Doblin, MA & Hieb, KA 2004, 'Food web pathway determines how selenium affects aquatic ecosystems: A San Francisco Bay case study', Environmental Science & Technology, vol. 38, no. 17, pp. 4519-4526.View/Download from: Publisher's site
Chemical contaminants disrupt ecosystems, but specific effects may be under-appreciated when poorly known processes such as uptake mechanisms, uptake via diet, food preferences, and food web dynamics are influential. Here we show that a combination of food web structure and the physiology of trace element accumulation explain why some species in San Francisco Bay are threatened by a relatively low level of selenium contamination and some are not. Bivalves and crustacean zooplankton form the base of two dominant food webs in estuaries, The dominant bivalve Potamocorbula amurensis has a 10-fold slower rate constant of loss for selenium than do common crustaceans such as copepods and the mysid Neomysis mercedis (rate constant of loss, k(e) = 0.025, 0.155, and 0.25 d(-1), respectively). The result is much higher selenium concentrations in the bivalve than in the crustaceans. Stable isotope analyses show that this difference is propagated up the respective food webs in San Francisco Bay. Several predators of bivalves have tissue concentrations of selenium that exceed thresholds thought to be associated with teratogenesis or reproductive failure (liver Se > 15 mug g(-1) dry weight). Deformities typical of selenium-induced teratogenesis were observed in one of these species. Concentrations of selenium in tissues of predators of zooplankton are less than the thresholds. Basic physiological and ecological processes can drive wide differences in exposure and effects among species, but such processes are rarely considered in traditional evaluations of contaminant impacts.
Purkerson, DG, Doblin, MA, Bollens, SM, Luoma, SN & Cutter, GA 2003, 'Selenium in San Francisco Bay zooplankton: Potential effects of hydrodynamics and food web interactions', Estuaries, vol. 26, no. 4A, pp. 956-969.View/Download from: Publisher's site
The potential toxicity of elevated selenium (Se) concentrations in aquatic ecosystems has stimulated efforts to measure Se concentrations in benthos, nekton, and waterfowl in San Francisco Bay (SF Bay). In September 1998, we initiated a 14 mo field study to determine the concentration of Se in SF Bay zooplankton, which play a major role in the Bay food web, but which have not previously been studied with respect to Se. Monthly vertical plankton tows were collected at several stations throughout SF Bay, and zooplankton were separated into two operationally defined size classes for Se analyses: 73-2,000 mum, and greater than or equal to2,000 mum. Selenium values ranged 1.02-6.07 mug Se g(-1) dry weight. No spatial differences in zooplankton Se concentrations were found. However, there were inter- and intra-annual differences. Zooplankton Se concentrations were enriched in the North Bay in Fall 1999 when compared to other seasons and locations within and outside SF Bay. The abundance and biovolume of the zooplankton community varied spatially between stations, but not seasonally within each station. Smaller herbivorous-omnivorous zooplankton had higher Se concentrations than larger omnivorous-carnivorous zooplankton. Selenium concentrations in zooplankton were negatively correlated with the proportion of total copepod biovolume comprising the large carnivorous copepod Tortanus dextrilobatus, but positively correlated with the proportion of copepod biovolume comprising smaller copepods of the family Oithonidae, suggesting an important role of trophic level and size in regulating zooplankton Se concentrations.
Laroussi, M, Dobbs, FC, Wei, Z, Doblin, MA, Ball, LG, Moreira, K, Dyer, F & Richardson, J 2002, 'Decontamination of water by excimer UV radiation', IEEE Transactions On Plasma Science, vol. 30, no. 4, pp. 1501-1503.View/Download from: Publisher's site
Water is one of the most important substances on which life depends. However, water may also serve as a medium by which disease is spread to humans, animals, and plants. Therefore, the biological decontamination of this vital substance is of paramount im
Baines, SB, Fisher, NK, Doblin, MA & Cutter, GA 2001, 'Uptake of dissolved organic selenides by marine phytoplankton', Limnology And Oceanography, vol. 46, no. 8, pp. 1936-1944.View/Download from: Publisher's site
Se is present in multiple oxidation states in nature, each of which has unique chemical and biological reactivities. As a consequence, the rate of Se incorporation into food webs or its role as either a limiting nutrient or a toxic substance is a functio
Doblin, MA, Blackburn, S & Hallegraeff, GM 2000, 'Intraspecific variation in the selenium requirement of different geographic strains of the toxic dinoflagellate Gymnodinium catenatum', Journal Of Plankton Research, vol. 22, no. 3, pp. 421-432.View/Download from: Publisher's site
The requirement for selenium (IV) was assessed in five strains of the toxic dinoflagellate Gymnodinium catenatum Graham, representing three populations from Tasmania (Australia), as well as one each from Japan and Spain. Strains were grown in nutrient-en
Doblin, MA, Blackburn, S & Hallegraeff, GM 1999, 'Comparative study of selenium requirements of three phytoplankton species: Gymnodinium catenatum, Alexandrium minutum (Dinophyta) and Chaetoceros cf. tenuissimus (Bacillariophyta)', Journal Of Plankton Research, vol. 21, no. 6, pp. 1153-1169.View/Download from: Publisher's site
This study investigated the selenium (Se) requirements of three phytoplankton species which commonly bloom in southern Australian estuaries. The present study showed that the toxic dinoflagellate Gymnodinium catenatum Graham had an obligate requirement f
Doblin, MA, Blackburn, S & Hallegraeff, GM 1999, 'Growth and biomass stimulation of the toxic dinoflagellate Gymnodinium catenatum (Graham) by dissolved organic substances', Journal Of Experimental Marine Biology And Ecology, vol. 236, no. 1, pp. 33-47.View/Download from: Publisher's site
Blooms of the toxic dinoflagellate Gymnodinium catenatum are annually recurrent events in south-east Tasmanian waters. Extensive blooms are preceded by a rainfall trigger and the associated influx of dissolved organic matter (DOM; otherwise known as humi
Doblin, MA & Clayton, MN 1995, 'Effects Of Secondarily Treated Sewage Effluent On The Early Life-History Stages Of 2 Species Of Brown Macroalgae - Hormosira-Banksii And Durvillaea-Potatorum', Marine Biology, vol. 122, no. 4, pp. 689-698.View/Download from: Publisher's site
Sewage effluent has a deleterious effect on the early life-history stages of Hosmosira banksii (Turner) Decaisne and Durvillaea potatorum (Labillardiere) Areschoug. High concentrations of sewage effluent (28 and 40% in seawater) inhibit zygote germinatio
Bouman, HA, Platt, T, Doblin, M, Figueiras, FG, Gudmudsson, K, Gudfinnsson, HG, Huang, B, Hickman, A, Hiscock, M, Jackson, T, Lutz, VA, Mélin, F, Rey, F, Pepin, P, Segura, V, Tilstone, GH, van Dongen-Vogels, V & Sathyendranath, S, 'Photosynthesis-irradiance parameters of marine phytoplankton: synthesis of a global data set'.View/Download from: Publisher's site
Abstract. The photosynthetic performance of marine phytoplankton varies in response to a variety of factors, environmental and taxonomic. One of the aims of the MArine primary Production: model Parameters from Space (MAPPS) project of the European Space Agency is to assemble a global database of photosynthesis-irradiance (P-E) parameters from a range of oceanographic regimes as an aid to examining the basin-scale variability in the photophysiological response of marine phytoplankton and to use this information to improve the assignment of P-E parameters in the estimation of global marine primary production using satellite data. The MAPPS P-E Database, which consists of over 5000 P-E experiments, provides information on the spatio-temporal variability in the two P-E parameters (the assimilation number, PmB, and the initial slope, αB, where the superscripts B indicate normalisation to concentration of chlorophyll) that are fundamental inputs for models (satellite-based and otherwise) of marine primary production that use chlorophyll as the state variable. Quality-control measures consisted of removing samples with abnormally-high parameter values and flags were added to denote whether the spectral quality of the incubator lamp was used to calculate a broad-band value of αB. The MAPPS database provides a photophysiological dataset that is unprecedented in number of observations and in spatial coverage. The database would be useful to a variety of research communities, including marine ecologists, biogeochemical modellers, remote-sensing scientists and algal physiologists. The compiled data are available at https://doi.org/10.1594/PANGAEA.874087 (Bouman et al., 2017).
© Springer International Publishing AG 2017. Viruses, bacteria, archaea and single celled eukaryotes, collectively known as microbes, dominate the biomass and metabolism of ocean ecosystems. Marine microbes are highly abundant and critical to human survival, but the vast majority of taxa have not yet been cultured. The use of environmental nucleic acid sequencing as a cultivation-independent approach to microbial oceanography has therefore significantly expanded our understanding of the diversity, evolution, biogeography and important biogeochemical roles of marine microorganisms. Here we provide illustrative examples of how genomic, transcriptomic and proteomic approaches have been applied to marine microbes to advance our understanding of their ecology. A remaining challenge is the need to link phenotypes to their environment, requiring a better understanding of genomic features that influence transcription (e.g. promoters and methylation) as well as post-translational modifications, and how such regulatory processes are impacted by extracellular abiotic and biotic processes. In addition, the expansion of available protein and taxonomic databases will greatly increase our capacity to link microbial function to specific taxa.
Ralph, PJ, Hill, R, Doblin, MA & Davy, SK 2016, 'Theory and Application of Pulse Amplitude Modulated Chlorophyll Fluorometry in Coral Health Assessment' in Woodley, CM, Downs, CA, Bruckner, AW, Porter, JW & Galloway, SB (eds), Diseases of Coral, John Wiley & Sons, Hoboken, New Jersey, pp. 506-523.View/Download from: Publisher's site
© 2016 John Wiley & Sons, Inc. Scleractinian corals exist in symbiosis with dinoflagellate alga (genus Symbiodinium), which provides access to nutrients by the host but also makes it makes the holobiont vulnerable to photosynthetic stress, providing an opportunity for rapid health assessment using chlorophyll a (chl-a) fluorescence techniques. Common photosynthetic stressors of corals are high irradiance, ultraviolet light, temperature extremes, chemical pollution and low salinity, which are further compounded by other major anthropogenic pressures on coral reefs. Coral Symbiodinium cells contain chlorophyll (chl) a, c2 and a range of accessory pigments. The chl-a within the pigment complex absorbs light maximally in the blue (peak at 440 nm) and red (peak at 678 nm) regions of the spectrum and re-emits light energy in the form of fluorescence, maximally in the red bandwidth (630 to 770 m with a peak at 680 nm). In vivo chl-a has a variable fluorescence yield that is dependent upon the wavelength of excitation irradiance and varies over time as a result of the complex interaction of the photosynthetic pathways (Kautsky effect). When a chloroplast captures a photon of energy, the chl a molecule is excited from its ground state to an excited state. There are three competing and complementary energy dissipation processes for that excited molecule: (i) driving photosynthesis via the electron transport chain leading to carbon fixation, (ii) heat dissipation, or (iii) returning to the ground state and re-emitting some of the energy as fluorescence. This is why chl a fluorescence can be used as a proxy for photochemistry (and energy dissipation). During periods of high incident irradiance, if the amount of absorbed light exceeds the maximum rate of electron transport, then the excess energy must be dissipated, or photodamage can occur. Pulse-amplitude modulated (PAM) fluorometry provides a versatile technique for monitoring and assessing zooxanthellae health. It measure...
Schrameyer, V, Kraemer, W, Hill, R, Doblin, MA, Kai, B & Ralph, PJ 2010, 'Nutritional status of hard and soft corals influences photosynthesis capacity of Symbiodinium sp. and vitality of the holobiont', Euro ISRS Symposium 2010, Grafisch Service Center, Wageningen, The Netherlands, pp. 108-108.
Sinutok, S, Hill, R, Doblin, MA & Ralph, PJ 2010, 'Rising ocean temperature and ocean acidification will reduce productivity and calcification in Halimeda sp. and benthic foraminifera from the Great Barrier Reef', Euro ISRS Symposium 2010, Grafisch Service Center, Wageningen, The Netherlands, pp. 191-191.
Doblin, MA, Ralph, PJ, Oubelkheir, K, Hassler, CS, Suthers, I & Thompson, P 2009, 'Using IMOS to bridge the gap between direct measurements of marine primary production and models', Adelaide, Australia.
Petrou, K, Doblin, MA, Hassler, CS & Ralph, PJ 2009, 'Multiple stressors on the sea ice diatom Fragilariopsis cylindrus - photophysiological impacts of seasonal freezing and melting of sea ice', Japan.
Petrou, K, Shelly, K, Hassler, CS, Schoemann, V, Doblin, MA & Ralph, PJ 2007, 'Ocean productivity in a changing world: Iron-limitation of Southern Ocean phytoplankton and implication for Antarctic meltwater productivity', Australia.
Laroussi, M, Dobbs, FC, Wei, Z, Doblin, M, Ball, L, Moreira, K, Dyer, FF & Richardson, JP 2001, 'Effects of excimer UV radiation on microorganisms', IEEE International Conference on Plasma Science.
It is well known that under high pressure conditions, microdischarges in rare gases or rare gas/halogen mixtures produce excimers. Excimers do not possess a stable ground state and tend to decay rapidly, releasing in the process radiation in the VUV, UV, or even visible range. The radiation generated by excimer lamps is incoherent, but intense and spectrally selective. Therefore, excimer lamps have been used in numerous applications such as surface modification, paint curing, material deposition, and pollution abatement. In this paper, we report a series of experiments on the use of a Dielectric Barrier Discharge (DBD) based excimer UV lamp to decontaminate water (both fresh and salty). The lamp presents a large area with a cylindrical geometry, and is RF-driven. In our experimental setup, the lamp is immersed into about a half liter of water containing a pre-selected concentration of a specific microorganism. The volume of water is exposed to the UV radiation emanating from the lamp and samples are taken, at selected time intervals, for analysis. The microorganisms used in our experiments are Escherichia coli, Bacillus subtilis, and Salmonella typhimurium, all bacteria, and the dinoflagellate Gymnodinium catenatum. Kill curves showing viability versus treatment time will be presented. In addition, a characterization of the morphological changes of the treated cells will be attempted.
Laroussi, A, Dobbs, FC, Wei, Z, Doblin, A, Ball, L, Moreira, K, Dyer, FF & Richardson, JP, 'Effects of excimer UV radiation on microorganisms', IEEE Conference Record - Abstracts. PPPS-2001 Pulsed Power Plasma Science 2001. 28th IEEE International Conference on Plasma Science and 13th IEEE International Pulsed Power Conference (Cat. No.01CH37255), IEEE Conference Record - Abstracts. PPPS-2001 Pulsed Power Plasma Science 2001. 28th IEEE International Conference on Plasma Science and 13th IEEE International Pulsed Power Conference, IEEE.View/Download from: Publisher's site
Hallegraeff, GM, Beardall, J, Brett, S, Doblin, MA, Hosja, W, de Salas, M & Thompson, P www.oceanclimatechange.org.au 2009, Marine climate change in Australia: Impacts and adaptation responses: Phytoplankton, pp. 1-10, Australia.
Salas, M, Cheal, A, Lough, J, McKinnon, D, Meekan, M, Sweatman, H, Coleman, M, Chambers, L, Dunlop, N, Church, J, Dowdney, J, Feng, M, Griffiths, S, Hobday, A, Matear, R, Poloczanska, E, Richardson, A, Ridgway, K, Risbey, J, Thompson, P, Thresher, R, Weller, E, Saintilan, N, Wilson, S, Lenanton, R, Hosja, W, Moore, P, Wernberg, T, Marshall, D, Connolly, R, Hill, K, Congdon, B, Devney, C, Fuentes, M, Graham, N, Hamann, M, Kingsford, M, Munday, P, Pratchett, M, Sheaves, M, Beardall, J, Brett, S, Waschka, M, Dann, P, Edgar, G, Swadling, K, Connell, S, Russell, B, Ward, T, Lukoschek, V, McGregor, S, Jenkins, G, Campbell, A, Steinberg, P, Anthony, K, Lovelock, C, Skilleter, G, Figueira, WF, Booth, DJ, Doblin, MA, Davidson, J, Holbrook, N, Howard, W, Kendrick, G & Smale, D NCCARF Publication 2009, Report Card of Marine Climate Change for Australia, pp. 1-2, Australia.
As the base of the marine food web, and the first step in the biological carbon pump, understanding changes in microbial community composition is essential for predicting changes in the marine nitrogen (N) cycle. Climate change projections suggest that oligotrophic waters will become more stratified with a concomitant shift in microbial community composition based on changes in N supply. In regions of strong boundary currents, eddies could reduce this limitation through nutrient uplift and other forms of eddy mixing. Understanding the preference for different forms of N by microbes is essential for understanding and predicting shifts in the microbial community. This study aims to understand the utilization of different N species within different microbial size fractions as well as understand the preferred source of N to these groups across varying mesoscale and sub-mesoscale features in the East Australian Current (EAC). In June 2015 we sampled microbial communities from three depths (surface, chlorophyll-a maximum and below the mixed layer), in three mesoscale and sub-mesoscale eddy features, as well as two end-point water masses (coastal and oligotrophic EAC water). Particulate matter was analysed for stable C and N isotopes, and seawater incubations with trace amounts of 15NO3, 15NH4, 15N2, 15Urea and 13C were undertaken. All samples were size fractionated into 0.3-2.0 µm, 2.0-10 µm, and >10 µm size classes, encompassing the majority of microbes in these waters. Microbial community composition was also assessed (pigments, flow cytometry, DNA), as well as physical and chemical parameters, to better understand the drivers of carbon fixation and nitrogen utilization across a diversity of water masses and microbial size classes. We observed that small, young features have a greater abundance of larger size classes. We therefore predict that these microbes will preferentially draw down the recently pulsed NO3. Ultimately, the size and age of a feature will determin...
Hughes, DJ, Doblin, MA, Ralph, PJ, van Dongen-Vogels, V, Ingleton, T & Suggett, DJ 2015, 'NITROGEN AVAILABILITY DRIVES VARIABILITY OF THE ELECTRON REQUIREMENT FOR CARBON FIXATION IN COASTAL PHYTOPLANKTON COMMUNITIES'.
Baker, KG, Doblin, MA & Robinson, C 2015, 'THERMAL PERFORMANCE CURVES REVEAL ALTERNATIVE ENERGY PATHWAYS AT STRESSFUL TEMPERATURES: A MULTI-TRAIT ANALYSIS OF PHENOTYPIC PLASTICITY IN THALASSIOSIRA PSEUDONANA'.
- Integrated Marine Observing System
- Marine National Facility
- CSIRO Marine and Atmospheric Research
- Sydney Institute of Marine Science
- University of New South Wales, Macquarie University, University of Sydney, Curtin University
- University of Southern California, USA
- University of Edinburgh, UK