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Associate Professor David Suggett

Biography

I'm a marine biologist with research interests in photophysiology,and productivity of aquatic primary producers, ranging from microalgae to corals. Prior to joining UTS as an ARC Future Fellow I was a Postdoctoral Research Fellow, and then lecturer in Marine Biogeochemistry, at the University of Essex, UK.

At UTS I am a core member of The Climate Change Cluster (C3) where my research focuses on improving marine primary productivity estimates using advanced active fluorometry (bio-optical) approaches. The outcomes from this research will provide more accurate information on the health of Australian coastal waters and be used to improve Global Climate Models.

I am also the leader for the C3 Future Reefs research program

Professional

Scientific Advisor:
Over the past 10 years I have contributed to several working groups (e.g. The International Working Group for Coral Bleaching Forecast Modeling, and the Gulf of Mexico Ocean Observing System) and provided scientific advice to industries involved in development of sensors (e.g. fluorometers: Chelsea Technologies Group, Satlantic; chemiluminescence, Hills scientific), and in coral reef research (e.g. Operation Wallacea).

Conference Activity:
Session organiser/Chair "Interactive and repeat exposure effects of environmental perturbations upon corals and coral reef processes", ASLO Puerto Rico, 2011; Workshop Coordinator (open ocean) for the 8th GAP meeting (Eilat, Israel). Convener and chair of organising committee for ‘AQUAFLUO: Fluorescence in Aquatic systems’ international conference (Czech Republic, 2007).

Editorial:
Subject Editor (marine) for Global Change Biology (IF for 2013 = 6.91) since 2006

Review duties: Regular reviewer for journals Nature Climate Change, Limnology and Oceanography, Marine Ecology Progress Series, Journal of Phycology, Plant Cell & Environment, Coral Reefs, Photosynthesis Research; and for grant submissions for NERC and NSF research funding bodies.

Other:
I have previously served as the Assistant Director to the Coral Reef Research Unit (2005-2013), University of Essex; Member of the Natural Environmental Research Council (NERC) Peer Review College (2008-2012); Member of European Network of Excellence for Ocean Ecosystems Analysis (EUROCEANS) and American Society of Limnology and Oceanography (ASLO) and Phycological Society of America (PSA).

Awards:
2010 Fellow of the Challenger Society UK (outstanding contribution to marine biology/science by a young scientist)

Image of David Suggett
Future Fellow and Associate Professor, Climate Change Cluster
Core Member, Climate Change Cluster
B.Sc (Hons), M. Sc, Ph. D
 
Phone
+61 2 9514 1900

Research Interests

Microalgal photophysiology and productivity in aquatic environments: Coupling of light harvesting, electron turnover and carbon fixation in key marine microalgae; electron sinks under light-nutrient perturbations; Mechanisms of stress induction (reactive oxygen production) and protection;

Photosystem biophysics; Fluorescence as a tool in aquatic sciences: Use of variable fluorescence to quantify microalgal primary production; Mechanistic models of photosynthesis and photochemistry;

Physiology & ecology of coral reef organisms: Physiological and molecular (omic) properties of zooxanthellae (Symbiodinium spp.) genetic variants; Coral adaptation and acclimation to marginal reef environments; Environmental control of coral growth and resource allocation;

Impacts of climate change on marine productivity: Influence of ocean acidification on growth and resource allocation of phytoplankton and corals; thermal stress impacts (mechanisms of coral bleaching) upon corals; changing light environments and photophysiology/primary productivity;

Algal secondary metabolite production: Regulation of isoprene production by phototrophs; interaction of DMS and oxidative stress of corals.

Research Gate

Can supervise: Yes
I am Subject Co-ordinator for Coral Reef Ecosystems 91126

Books

Suggett, D.J., Borowitzka, M. & Prášil, O. 2010, Chlorophyll a Fluorescence in Aquatic Sciences: Methods and Applications, Springer Science & Business Media.
This book follows on from the first international conference on 'chlorophyll fluorescence in the aquatic sciences (AQUAFLUO 2007): to bridge the gaps between the concept, measurement and application of chlorophyll fluorescence through ...

Chapters

Geider, R.J., Moore, C.M. & Suggett, D.J. 2014, 'Ecology of Marine Phytoplankton' in Tester, M., Jorgensen, R. & Monson, R. (eds), The Plant Sciences, Springer New York, pp. 1-41.
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Hennige, S.J., Suggett, D.J., Hepburn, L.J., Pugsley, A., Crabbe, J. & Smith, D.J. 2013, 'Coral reefs of the Wakatobi: Processes of reef growth and loss' in Marine Research and Conservation in the Coral Triangle, pp. 27-44.
Coral reef accretion (net reef growth) is the result of complex and dynamic interactions between reef building organisms, bioeroders and the environment. Coral calcification often forms the 'measureable' portion of net reef growth, and is dependent upon the successful symbiotic relationship between cnidaria and photosynthetic dinoflagellate microalgae (Symbiodinium spp.). Light is thus a crucial resource for coral growth. Processes of reef loss include abiotic (storms, disturbance events and climate change) and biotic (bioeroders and corralivores) factors. To assess reef accretion, an understanding of the relationship between coral growth and loss, environmental variables and biotic eroders is vital. Reef systems that have both high biodiversity and varied environmental conditions are prime 'study grounds' to assess these complex interactions. An important example is the Wakatobi National Park (WNP), which is a centre for biodiversity but also has active long-term projects across a range of environments. This chapter examines the underlying physiology of the coral symbiotic relationship, and how this relates to reef growth by using studies from both the WNP and other systems. Understanding these processes remains a critical first step in any reef management strategy plan, but current methods by which reef growth can be assessed often lack the resolution and accuracy needed to relate to changes of environment. Consequently, this chapter discusses benefits and limitations of certain techniques used to assess reef growth. Ultimately, accurate coral growth measurements will improve our ability to model future ecosystem change, and should therefore be a priority research area to support future reef management and conservation strategies. Processes of reef loss are then discussed with regard to the impact of bioeroders, environmental perturbations and anthropogenic stressors upon primary and secondary reef framework. © 2010 by Nova Science Publishers, Inc. All rights r...
Suggett, D.J. & Moore, C.M. 2010, 'Fluorometry for Biological Sensing' in Encyclopedia of Ocean Sciences, pp. 581-588.
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Light-absorbing pigments cause many marine organisms to naturally fluoresce, a phenomenon whereby light is emitted at a longer wavelength following light absorption at a shorter wavelength. Fluorescence provides a relatively unobtrusive signature of organism abundance and physiology; consequently, a wide variety of fluorescence techniques are now routinely employed in marine biological investigations. Important technological advances throughout the last 20 years have enabled exploration of the taxonomy and physiology of marine organisms with increasing complexity. In particular, the intracellular use of fluorescent tags, molecules, and dyes that covalently bind to sensing biomolecules. However, many such techniques require samples to be removed from nature. Most widespread for assaying biology in situ exploits the fluorescence emitted from chlorophyll a, the predominant light harvesting pigment inherent to all (micro)algae, cyanobacteria, and aquatic vascular plants. Measurements of chlorophyll a fluorescence were introduced in the 1960s to improve estimates of phytoplankton abundance. By the 1990s, this field had evolved to enable the physiology and productivity of primary producers to be examined at scales from the single cell to entire ocean basins. Current remote sensing algorithms concentrate on better describing the relationship between primary productivity and natural fluorescence that is emitted from solar excitation. While several major challenges exist in achieving this goal, such approaches provide great promise for accurately characterizing the role of marine primary productivity during this period of extreme climate change. © 2009 Copyright © 2009 Elsevier Ltd. All rights reserved.
Suggett, D.J., Moore, C.M. & Geider, R.J. 2010, 'Estimating Aquatic Productivity from Active Fluorescence Measurements' in Suggett, D.J., Prasil, O. & Borowitzka, M. (eds), Chlorophyll a Fluorescence in Aquatic Sciences: Methods and Applications, Springer Science & Business Media, 15, pp. 103-127.
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This book follows on from the first international conference on 'chlorophyll fluorescence in the aquatic sciences (AQUAFLUO 2007): to bridge the gaps between the concept, measurement and application of chlorophyll fluorescence through ...

Journal articles

Levin, R.A., Suggett, D.J., Nitschke, M.R., van Oppen, M.J.H. & Steinberg, P.D. 2017, 'Expanding the Symbiodinium (Dinophyceae, Suessiales) Toolkit Through Protoplast Technology.', J Eukaryot Microbiol.
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Dinoflagellates within the genus Symbiodinium are photosymbionts of many tropical reef invertebrates, including corals, making them central to the health of coral reefs. Symbiodinium have therefore gained significant research attention, though studies have been constrained by technical limitations. In particular, the generation of viable cells with their cell walls removed (termed protoplasts) has enabled a wide range of experimental techniques for bacteria, fungi, plants, and algae such as ultrastructure studies, virus infection studies, patch clamping, genetic transformation, and protoplast fusion. However, previous studies have struggled to remove the cell walls from armored dinoflagellates, potentially due to the internal placement of their cell walls. Here we produce the first Symbiodinium protoplasts from three genetically and physiologically distinct strains via incubation with cellulase and osmotic agents. Digestion of the cell walls was verified by a lack of Calcofluor White fluorescence signal and by cell swelling in hypotonic culture medium. Fused protoplasts were also observed, motivating future investigation into intra- and inter-specific somatic hybridization of Symbiodinium. Following digestion and transfer to regeneration medium, protoplasts remained photosynthetically active, regrew cell walls, regained motility, and entered exponential growth. Generation of Symbiodinium protoplasts opens exciting, new avenues for researching these crucial symbiotic dinoflagellates, including genetic modification. This article is protected by copyright. All rights reserved.
Wangpraseurt, D., Holm, J.B., Larkum, A.W.D., Pernice, M., Ralph, P.J., Suggett, D.J. & Kühl, M. 2017, 'In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop?', Front Microbiol, vol. 8, p. 59.
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Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching.
Goyen, S., Pernice, M., Szabó, M., Warner, M.E., Ralph, P.J. & Suggett, D.J. 2017, 'A molecular physiology basis for functional diversity of hydrogen peroxide production amongst Symbiodinium spp. (Dinophyceae)', Marine Biology, vol. 164, no. 3.
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© 2017, Springer-Verlag Berlin Heidelberg.Hydrogen peroxide (H2O2) production has been demonstrated to play a pivotal role in the photosynthetic stability of higher plants, corals and algae, and considered a primary reactive oxygen species (ROS) associated with the thermal susceptibility of Symbiodinium spp. Here, we simultaneously subjected a large number of Symbiodinium isolates (n = 16) covering broad phylogenetic diversity (clades A, B, D, F) to heat stress and characterized their photosynthetic response via fast repetition rate fluorometry (FRRf) and parallel measurements of H2O2 emissions. Based on their physiological response, isolates clustered into three novel functional groups: (1) thermally tolerant (unchanged photochemical efficiency (Fv/Fm), electron turnover (QA) or H2O2 emission), or (2) thermally susceptible via decreased Fv/Fm, unchanged QA, but increased H2O2, indicating energetically uncoupled PSII (thylakoid membrane instability), versus (3) thermally responsive via decreased Fv/Fm, increased QA and H2O2, indicative of energetically coupled (but downregulated) PSII. There was no correlation between the algal phylogenetic groups and the distribution of isolates amongst these novel functional groups. Two model Symbiodinium isolates for functional groups (1) and (2) (ITS2 type A1, Symbiodinium microadriaticum, and type D1–5, Symbiodinium spp., respectively) were selected to further examine how their different thermal responses corresponded with the expression levels of two genes coding for different metalloforms of superoxide dismutase (MnSOD and NiSOD) that potentially regulate production of H2O2. S. microadriaticum demonstrated the greatest upregulation of MnSOD gene confirming recent suggestions of a role for this metalloform in the antioxidant network associated with thermal stress protection. Assigning Symbiodinium isolates into such functional groups based on coupled molecular-physiological assessment is an important step needed to impro...
Murray, S.A., Suggett, D.J., Seymour, J.R., Doblin, M., Kohli, G.S., Fabris, M. & Ralph, P.J. 2016, 'Unravelling the functional genetics of dinoflagellates: a review of approaches and opportunities', Perspectives in Phycology, vol. 3, no. 1, pp. 37-52.
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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.
Zhu, Y., Ishizaka, J., Tripathy, S.C., Wang, S., Mino, Y., Matsuno, T. & Suggett, D.J. 2016, 'Variation of the photosynthetic electron transfer rate and electron requirement for daily net carbon fixation in Ariake Bay, Japan', Journal of Oceanography, vol. 72, no. 5, pp. 761-776.
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The Oceanographic Society of Japan and Springer Japan Fast repetition rate fluorometry (FRRf) provides a potential means to examine marine primary productivity; however, FRRf-based productivity estimations require knowledge of the electron requirement (K) for carbon (C) uptake (KC) to scale an electron transfer rate (ETR) to the CO2 uptake rate. Most previous studies have derived KC from parallel measurements of ETR and CO2 uptake over relatively short incubations, with few from longer-term daily-integrated periods. Here we determined KC by comparing depth-specific, daily ETRs and CO2-uptake rates obtained from 24-h on-deck incubation experiments undertaken on seven cruises in Ariake Bay, Japan, from 2008 to 2010. The purpose of this study was to determine the extent of variability of KC and to what extent this variability could be reconciled with the prevailing environmental conditions and ultimately to develop a method for determining net primary productivity (NPP) based on FRRf measurements. Both daily ETR and KC of the upper layer varied considerably, from 0.5 to 115.7 mmol e mg Chl-a1 day1 and 4.1–26.6 mol e (mol C)1, respectively, throughout the entire data set. Multivariate analysis revealed a strong correlation between daily photosynthetically active radiation (PAR) and KC (r2 = 0.94). A simple PAR-dependent relationship derived from the data set was used for generating KC, and this relationship was validated by comparing the FRRf-predicted NPP with the 13C uptake measured in 2007. These new observations demonstrate the potential application of FRRf for estimating regional NPP from ETR.
Camp, E.F., Smith, D.J., Evenhuis, C., Enochs, I., Manzello, D., Woodcock, S. & Suggett, D.J. 2016, 'Acclimatization to high-variance habitats does not enhance physiological tolerance of two key Caribbean corals to future temperature and pH.', Proceedings. Biological sciences / The Royal Society, vol. 283, no. 1831.
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Corals are acclimatized to populate dynamic habitats that neighbour coral reefs. Habitats such as seagrass beds exhibit broad diel changes in temperature and pH that routinely expose corals to conditions predicted for reefs over the next 50-100 years. However, whether such acclimatization effectively enhances physiological tolerance to, and hence provides refuge against, future climate scenarios remains unknown. Also, whether corals living in low-variance habitats can tolerate present-day high-variance conditions remains untested. We experimentally examined how pH and temperature predicted for the year 2100 affects the growth and physiology of two dominant Caribbean corals (Acropora palmata and Porites astreoides) native to habitats with intrinsically low (outer-reef terrace, LV) and/or high (neighbouring seagrass, HV) environmental variance. Under present-day temperature and pH, growth and metabolic rates (calcification, respiration and photosynthesis) were unchanged for HV versus LV populations. Superimposing future climate scenarios onto the HV and LV conditions did not result in any enhanced tolerance to colonies native to HV. Calcification rates were always lower for elevated temperature and/or reduced pH. Together, these results suggest that seagrass habitats may not serve as refugia against climate change if the magnitude of future temperature and pH changes is equivalent to neighbouring reef habitats.
Camp, E.F., Suggett, D.J., Gendron, G., Jompa, J., Manfrino, C. & Smith, D.J. 2016, 'Mangrove and Seagrass Beds Provide Different Biogeochemical Services for Corals Threatened by Climate Change', Frontiers in Marine Science, vol. 3, pp. 1-16.
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Rapidly rising atmospheric CO2 concentrations are driving acidification in parallel with warming of the oceans. Future ocean acidification scenarios have the potential to impact coral growth and associated reef function, although reports suggest such affects could be reduced in adjacent seagrass habitats as a result of physio-chemical buffering. To-date, it remains unknown whether these habitats can actually support the metabolic function of a diverse range of corals. Similarly, whether mangroves provide the same ecological buffering service remains unclear. We examine whether reef-associated habitat sites (seagrass and mangroves) can act as potential refugia to future climate change by maintaining favorable chemical conditions (elevated pH and aragonite saturation state relative to the open-ocean), but by also assessing whether the metabolic function (photosynthesis, respiration and calcification) of important reef-building corals are sustained. We investigated three sites in the Atlantic, Indian, and Pacific Oceans and consistently observed that seagrass beds experience an overall elevation in mean pH (8.15 ± 0.01) relative to the adjacent outer-reef (8.12 ± 0.03), but with periods of high and low pH. Corals in the seagrass habitats either sustained calcification or experienced an average reduction of 17.0 ± 6.1% relative to the outer-reef. In contrast, mangrove habitats were characterized by a low mean pH (8.04 ± 0.01) and a relatively moderate pH range. Corals within mangrove-dominated habitats were thus pre-conditioned to low pH but with significant suppression to calcification (70.0 ± 7.3% reduction relative to the outer-reef). Both habitats also experienced more variable temperatures (diel range up to 2.5C) relative to the outer-reef (diel range less than 0.7C), which did not correspond with changes in calcification rates. Here we report, for the first time, the biological costs for corals living in reef-associated habitats and characterize the environme...
Camp, E.F., Dong, L.F., Suggett, D.J., Smith, D.J., Boatman, T.G., Crosswell, J.R., Evenhuis, C., Scorfield, S., Walinjkar, A., Woods, J. & Lawson, T. 2016, 'A novel membrane inlet-infrared gas analysis (MI-IRGA) system for monitoring of seawater carbonate system', Limnology and Oceanography: Methods.
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© 2016 Association for the Sciences of Limnology and Oceanography.Increased atmospheric CO2 concentrations are driving changes in ocean chemistry at unprecedented rates resulting in ocean acidification, which is predicted to impact the functioning of marine biota, in particular of marine calcifiers. However, the precise understanding of such impacts relies on an analytical system that determines the mechanisms and impact of elevated pCO2 on the physiology of organisms at scales from species to entire communities. Recent work has highlighted the need within experiments to control all aspects of the carbonate system to resolve the role of different inorganic carbon species on the physiological responses observed across taxa in real-time. Presently however, there are limited options available for continuous quantification of physiological responses, coupled with real-time calculation of the seawater carbonate chemistry system within microcosm environments. Here, we describe and characterise the performance of a novel pCO2 membrane equilibrium system (the Membrane Inlet Infra-Red Gas Analyser, MI-IRGA) integrated with a continuous pH and oxygen monitoring platform. The system can detect changes in the seawater carbonate chemistry and determine organism physiological responses, while providing the user with real-time control over the microcosm system. We evaluate the systems control, response time and associated error, and demonstrate the flexibility of the system to operate under field conditions and within a laboratory. We use the system to measure physiological parameters (photosynthesis and respiration) for the corals Pocillipora damicornis and Porites cylindrica; in doing so we present a novel dataset examining the interactive role of temperature, light and pCO2 on the physiology of P. cylindrica.
Hopkins, F.E., Bell, T.G., Yang, M., Suggett, D.J. & Steinke, M. 2016, 'Air exposure of coral is a significant source of dimethylsulfide (DMS) to the atmosphere.', Sci Rep, vol. 6, p. 36031.
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Corals are prolific producers of dimethylsulfoniopropionate (DMSP). High atmospheric concentrations of the DMSP breakdown product dimethylsulfide (DMS) have been linked to coral reefs during low tides. DMS is a potentially key sulfur source to the tropical atmosphere, but DMS emission from corals during tidal exposure is not well quantified. Here we show that gas phase DMS concentrations (DMSgas) increased by an order of magnitude when three Indo-Pacific corals were exposed to air in laboratory experiments. Upon re-submersion, an additional rapid rise in DMSgas was observed, reflecting increased production by the coral and/or dissolution of DMS-rich mucus formed by the coral during air exposure. Depletion in DMS following re-submersion was likely due to biologically-driven conversion of DMS to dimethylsulfoxide (DMSO). Fast Repetition Rate fluorometry showed downregulated photosynthesis during air exposure but rapid recovery upon re-submersion, suggesting that DMS enhances coral tolerance to oxidative stress during a process that can induce photoinhibition. We estimate that DMS emission from exposed coral reefs may be comparable in magnitude to emissions from other marine DMS hotspots. Coral DMS emission likely comprises a regular and significant source of sulfur to the tropical marine atmosphere, which is currently unrecognised in global DMS emission estimates and Earth System Models.
Murphy, C.D., Ni, G., Li, G., Barnett, A., Xu, K., Grant-Burt, J., Liefer, J.D., Suggett, D.J. & Campbell, D.A. 2016, 'Quantitating active photosystem II reaction center content from fluorescence induction transients', Limnology and Oceanography: Methods.
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© 2016 Association for the Sciences of Limnology and Oceanography.Photosystem II (PSII) is a pigment-protein complex that photochemically extracts electrons from water, generating the reductant that supports biological productivity in all biomes. Estimating the content of active PSII reaction centers in a liquid sample is a key input for estimating aquatic photosynthesis rates, as well as for analyzing phytoplankton stress responses. Established procedures for PSII content quantification based on oxygen evolution are slow, imprecise and require dense cell suspensions, and are thus inapplicable to many laboratory or field studies. A new approach uses baseline chlorophyll fluorescence emission divided by the effective absorbance cross section for PSII photochemistry, with both variables derivable from single turnover fluorescence induction protocols. This approach has not been widely tested and is potentially subject to variation in samples suffering progressive photoinactivation or induction of non-photochemical quenching under variable light. We evaluated the validity of this approach for a marine picocyanobacteria, low and high light Prochlorococcus ecotypes, arctic and temperate prasinophyte green alga and two centric diatoms, generating 209 paired determinations from a range of growth and treatment conditions. We successfully calibrated the fluorescence derived estimator for PSII reaction center content, and demonstrate a modification that corrects for the short term influence of photoinactivation. The modified parameter shows little response to induction of non-photochemical quenching. In doing so we show the potential and limitations of an estimator of active PSII reaction center content that is sufficiently robust to support rapid, time-resolved autonomous measures of primary productivity from lakes and oceans.
Exton, D.A., McGenity, T.J., Steinke, M., Smith, D.J. & Suggett, D.J. 2015, 'Uncovering the volatile nature of tropical coastal marine ecosystems in a changing world.', Global change biology, vol. 21, no. 4, pp. 1383-1394.
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Biogenic volatile organic compounds (BVOCs), in particular dimethyl sulphide (DMS) and isoprene, have fundamental ecological, physiological and climatic roles. Our current understanding of these roles is almost exclusively established from terrestrial or oceanic environments but signifies a potentially major, but largely unknown, role for BVOCs in tropical coastal marine ecosystems. The tropical coast is a transition zone between the land and ocean, characterized by highly productive and biodiverse coral reefs, seagrass beds and mangroves, which house primary producers that are amongst the greatest emitters of BVOCs on the planet. Here, we synthesize our existing understanding of BVOC emissions to produce a novel conceptual framework of the tropical marine coast as a continuum from DMS-dominated reef producers to isoprene-dominated mangroves. We use existing and previously unpublished data to consider how current environmental conditions shape BVOC production across the tropical coastal continuum, and in turn how BVOCs can regulate environmental stress tolerance or species interactions via infochemical networks. We use this as a framework to discuss how existing predictions of future tropical coastal BVOC emissions, and the roles they play, are effectively restricted to present day 'baseline' trends of BVOC production across species and environmental conditions; as such, there remains a critical need to focus research efforts on BVOC responses to rapidly accelerating anthropogenic impacts at local and regional scales. We highlight the complete lack of current knowledge required to understand the future ecological functioning of these important systems, and to predict whether feedback mechanisms are likely to regulate or exacerbate current climate change scenarios through environmentally and ecologically mediated changes to BVOC budgets at the ecosystem level.
Frommlet, J.C., Sousa, M.L., Alves, A., Vieira, S.I., Suggett, D.J. & Serôdio, J. 2015, 'Coral symbiotic algae calcify ex hospite in partnership with bacteria.', Proceedings of the National Academy of Sciences of the United States of America, vol. 112, no. 19, pp. 6158-6163.
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Dinoflagellates of the genus Symbiodinium are commonly recognized as invertebrate endosymbionts that are of central importance for the functioning of coral reef ecosystems. However, the endosymbiotic phase within Symbiodinium life history is inherently tied to a more cryptic free-living (ex hospite) phase that remains largely unexplored. Here we show that free-living Symbiodinium spp. in culture commonly form calcifying bacterial-algal communities that produce aragonitic spherulites and encase the dinoflagellates as endolithic cells. This process is driven by Symbiodinium photosynthesis but occurs only in partnership with bacteria. Our findings not only place dinoflagellates on the map of microbial-algal organomineralization processes but also point toward an endolithic phase in the Symbiodinium life history, a phenomenon that may provide new perspectives on the biology and ecology of Symbiodinium spp. and the evolutionary history of the coral-dinoflagellate symbiosis.
Suggett, D.J., Goyen, S., Evenhuis, C., Szabo, M., Pettay, D.T., Warner, M.E. & Ralph, P.J. 2015, 'Functional diversity of photobiological traits within the genus Symbiodinium appears to be governed by the interaction of cell size with cladal designation', New Phytologist, vol. 208, no. 2, pp. 370-381.
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© 2015 New Phytologist Trust. Dinoflagellates of the genus Symbiodinium express broad diversity in both genetic identity (phylogeny) and photosynthetic function to presumably optimize ecological success across extreme light environments; however, whether differences in the primary photobiological characteristics that govern photosynthetic optimization are ultimately a function of phylogeny is entirely unresolved. We applied a novel fast repetition rate fluorometry approach to screen genetically distinct Symbiodinium types (n = 18) spanning five clades (A-D, F) for potential phylogenetic trends in factors modulating light absorption (effective cross-section, reaction center content) and utilization (photochemical vs dynamic nonphotochemical quenching; [1 - C] vs [1 - Q]) by photosystem II (PSII). The variability of PSII light absorption was independent of phylogenetic designation, but closely correlated with cell size across types, whereas PSII light utilization intriguingly followed one of three characteristic patterns: (1) similar reliance on [1 - C] and [1 - Q] or (2) preferential reliance on [1 - C] (mostly A, B types) vs (3) preferential reliance on [1 - Q] (mostly C, D, F types), and thus generally consistent with cladal designation. Our functional trait-based approach shows, for the first time, how Symbiodinium photosynthetic function is governed by the interplay between phylogenetically dependent and independent traits, and is potentially a means to reconcile complex biogeographic patterns of Symbiodinium phylogenetic diversity in nature.
Barnes, M.K., Barnes, M.K., Tilstone, G.H., Smyth, T.J., Widdicombe, C.E., Gloël, J., Gloël, J., Robinson, C., Kaiser, J. & Suggett, D.J. 2015, 'Drivers and effects of Karenia mikimotoi blooms in the western English Channel', Progress in Oceanography, vol. 137, no. B, pp. 456-469.
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&copy; 2015. Naturally occurring red tides and harmful algal blooms (HABs) are of increasing importance in the coastal environment and can have dramatic effects on coastal benthic and epipelagic communities worldwide. Such blooms are often unpredictable, irregular or of short duration, and thus determining the underlying driving factors is problematic. The dinoflagellate Karenia mikimotoi is an HAB, commonly found in the western English Channel and thought to be responsible for occasional mass finfish and benthic mortalities. We analysed a 19-year coastal time series of phytoplankton biomass to examine the seasonality and interannual variability of K. mikimotoi in the western English Channel and determine both the primary environmental drivers of these blooms as well as the effects on phytoplankton productivity and oxygen conditions. We observed high variability in timing and magnitude of K. mikimotoi blooms, with abundances reaching >1000cellsmL<sup>-1</sup> at 10m depth, inducing up to a 12-fold increase in the phytoplankton carbon content of the water column. No long-term trends in the timing or magnitude of K. mikimotoi abundance were evident from the data. Key driving factors were identified as persistent summertime rainfall and the resultant input of low-salinity high-nutrient river water. The largest bloom in 2009 was associated with highest annual primary production and led to considerable oxygen depletion at depth, most likely as a result of enhanced biological breakdown of bloom material; however, this oxygen depletion may not affect zooplankton. Our data suggests that K. mikimotoi blooms are not only a key and consistent feature of western English Channel productivity, but importantly can potentially be predicted from knowledge of rainfall or river discharge.
Barnes, M.K., Tilstone, G.H., Suggett, D.J., Widdicombe, C.E., Bruun, J., Martinez-Vicente, V. & Smyth, T.J. 2015, 'Temporal variability in total, micro- and nano-phytoplankton primary production at a coastal site in the Western English Channel', Progress in Oceanography, vol. 137, no. B, pp. 470-483.
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&copy; 2015. Primary productivity and subsequent carbon cycling in the coastal zone have a significant impact on the global carbon budget. It is currently unclear how anthropogenic activity could alter these budgets but long term coastal time series of hydrological, biogeochemical and biological measurements represent a key means to better understand past drivers, and hence to predicting future seasonal and inter-annual variability in carbon fixation in coastal ecosystems. An 8-year time series of primary production from 2003 to 2010, estimated using a recently developed absorption-based algorithm, was used to determine the nature and extent of change in primary production at a coastal station (L4) in the Western English Channel (WEC). Analysis of the seasonal and inter-annual variability in production demonstrated that on average, nano- and pico-phytoplankton account for 48% of the total carbon fixation and micro-phytoplankton for 52%. A recent decline in the primary production of nano- and pico-phytoplankton from 2005 to 2010 was observed, corresponding with a decrease in winter nutrient concentrations and a decrease in the biomass of Phaeocystis sp. Micro-phytoplankton primary production (PP<inf>M</inf>) remained relatively constant over the time series and was enhanced in summer during periods of high precipitation. Increases in sea surface temperature, and decreases in wind speeds and salinity were associated with later spring maxima in PP<inf>M</inf>. Together these trends indicate that predicted increases in temperature and decrease in wind speeds in future would drive later spring production whilst predicted increases in precipitation would also continue these blooms throughout the summer at this site.
Tamburic, B., Evenhuis, C.R., Suggett, D.J., Larkum, A.W.D., Raven, J.A. & Ralph, P.J. 2015, 'Gas Transfer Controls Carbon Limitation During Biomass Production by Marine Microalgae', CHEMSUSCHEM, vol. 8, no. 16, pp. 2727-2736.
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Fujise, L., Suggett, D.J., Frommlet, J.C., Serodio, J. & Ralph, P.J. 2015, 'TURNING UP THE HEAT ON SYMBIODINIUM CELL CYCLE ANALYSIS', EUROPEAN JOURNAL OF PHYCOLOGY, vol. 50, pp. 58-59.
Silsbe, G.M., Oxborough, K., Suggett, D.J., Forster, R.M., Ihnken, S., Komarek, O., Lawrenz, E., Prasil, O., Rottgers, R., Sicner, M., Simis, S.G.H., Van Dijk, M.A. & Kromkamp, J.C. 2015, 'Toward autonomous measurements of photosynthetic electron transport rates: An evaluation of active fluorescence-based measurements of photochemistry', Limnology and Oceanography: Methods, vol. 13, no. 3, pp. 138-155.
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Camp, E.F., Krause, S.L., Santos, L.M.F., Naumann, M.S., Kikuchi, R.K.P., Smith, D.J., Wild, C. & Suggett, D.J. 2015, 'The 'Flexi-Chamber: A Novel Cost-Effective In Situ Respirometry Chamber for Coral Physiological Measurements', PLoS One, vol. 10, no. 10, pp. 1-21.
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Barnes, M.K., Tilstone, G.H., Smyth, T.J., Suggett, D.J., Astoreca, R., Lancelot, C. & Kromkamp, J.C. 2014, 'Absorption-based algorithm of primary production for total and size-fractionated phytoplankton in coastal waters', Marine Ecology Progress Series, vol. 504, pp. 73-89.
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Most satellite models of production have been designed and calibrated for use in the open ocean. Coastal waters are optically more complex, and the use of chlorophyll a (chl a) as a first-order predictor of primary production may lead to substantial errors due to significant quantities of coloured dissolved organic matter (CDOM) and total suspended material (TSM) within the first optical depth. We demonstrate the use of phytoplankton absorption as a proxy to estimate primary production in the coastal waters of the North Sea and Western English Channel for both total, micro- and nano+pico-phytoplankton production. The method is implemented to extrapolate the absorption coefficient of phytoplankton and production at the sea surface to depth to give integrated fields of total and micro- and nano+pico-phytoplankton primary production using the peak in absorption coefficient at red wavelengths. The model is accurate to 8% in the Western English Channel and 22% in this region and the North Sea. By comparison, the accuracy of similar chl a based production models was >250%. The applicability of the method to autonomous optical sensors and remotely sensed aircraft data in both coastal and estuarine environments is discussed.
Wu, Y., Campbell, D.A., Irwin, A.J., Suggett, D.J. & Finkel, Z. 2014, 'Ocean acidification enhances the growth rate of larger diatoms', Limnology and Oceanography, vol. 59, no. 3, pp. 1027-1034.
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Ocean acidification is changing the nature of inorganic carbon availability in the global oceans. Diatoms account for ~ 40% of all marine primary productivity and are major contributors to the export of atmospheric carbon to the deep ocean. Larger diatoms are more likely to be stimulated by future increases in CO2 availability as a result of their low surface area to volume ratio and lower diffusive flux of CO2 relative to their carbon demand for growth. Here we quantify the effect of the partial pressure of carbon dioxide (), at levels of 190, 380, and 750 &micro;L L-1, on the growth rate, photosystem II electron transport rate (ETR), and elemental composition for five diatom species ranging over five orders of magnitude in cell volume. Growth rates for all species were enhanced under 750 relative to 190 and 380 &micro;L L-1, with little change in ETR or elemental stoichiometries, indicating an enhanced allocation of photochemical energy to growth under elevated . enhancement of growth rates was size dependent. Under 750 vs. 190 &micro;L L-1 partial pressures, growth rate was enhanced by ~ 5% for the smaller diatom species to ~ 30% for the largest species examined. The size dependence of CO2-stimulated growth enhancement indicates that ocean acidification may selectively favor an increase in the growth rates of larger vs. smaller phytoplankton species in the sea, with potentially significant consequences for carbon biochemistry.
Tamburic, B., Szabo, M., Tran, A., Larkum, A., Suggett, D.J. & Ralph, P.J. 2014, 'Action spectra of oxygen production and chlorophyll a fluorescence in the green microalga Nannochloropsis oculata', Bioresource Technology, vol. 169, pp. 320-327.
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The first complete action spectrum of oxygen evolution and chlorophyll a fluorescence was measured for the biofuel candidate alga Nannochloropsis oculata. A novel analytical procedure was used to generate a representative and reproducible action spectrum for microalgal cultures. The action spectrum was measured at 14 discrete wavelengths across the visible spectrum, at an equivalent photon flux density of 60 &micro;mol photons m-2 s-1. Blue light (~414 nm) was absorbed more efficiently and directed to photosystem II more effectively than red light (~679 nm) at light intensities below the photosaturation limit. Conversion of absorbed photons into photosynthetic oxygen evolution was maximised at 625 nm; however, this maximum is unstable since neighbouring wavelengths (646 nm) resulted in the lowest photosystem II operating efficiency. Identifying the wavelength-dependence of photosynthesis has clear implications to optimising growth efficiency and hence important economic implications to the algal biofuels and bioproducts industries.
Szabo, M., Wangpraseurt, D., Tamburic, B., Larkum, A., Schreiber, U., Suggett, D.J., Kühl, M. & Ralph, P.J. 2014, 'Effective light absorption and absolute electron transport rates in the coral Pocillopora damicornis', Plant Physiology and Biochemistry, vol. 83, pp. 159-167.
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Pulse Amplitude Modulation (PAM) fluorometry has been widely used to estimate the relative photosynthetic efficiency of corals. However, both the optical properties of intact corals as well as past technical constrains to PAM fluorometers have prevented calculations of the electron turnover rate of PSII. We used a new Multi-colour PAM (MC-PAM) in parallel with light microsensors to determine for the first time the wavelength-specific effective absorption cross-section of PSII photochemistry, sII(?), and thus PAM-based absolute electron transport rates of the coral photosymbiont Symbiodinium both in culture and in hospite in the coral Pocillopora damicornis. In both cases, sII of Symbiodinium was highest in the blue spectral region and showed a progressive decrease towards red wavelengths. Absolute values for sII at 440 nm were up to 1.5-times higher in culture than in hospite. Scalar irradiance within the living coral tissue was reduced by 20% in the blue when compared to the incident downwelling irradiance. Absolute electron transport rates of P. damicornis at 440 nm revealed a maximum PSII turnover rate of ca. 250 electrons PSII-1 s-1, consistent with one PSII turnover for every 4 photons absorbed by PSII; this likely reflects the limiting steps in electron transfer between PSII and PSI. Our results show that optical properties of the coral host strongly affect light use efficiency of Symbiodinium. Therefore, relative electron transport rates do not reflect the productivity rates (or indeed how the photosynthesis-light response is parameterised). Here we provide a non-invasive approach to estimate absolute electron transport rates in corals.
Robinson, C., Suggett, D.J., Cherukuru, N., Ralph, P.J. & Doblin, M.A. 2014, 'Performance of Fast Repetition Rate fluorometry based estimates of primary productivity in coastal waters', JOURNAL OF MARINE SYSTEMS, vol. 139, pp. 299-310.
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Wangpraseurt, D., Tamburic, B., Szabo, M., Suggett, D.J., Ralph, P.J. & Kuhl, M. 2014, 'Spectral Effects on Symbiodinium Photobiology Studied with a Programmable Light Engine', PLoS One.
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The spectral light field of Symbiodinium within the tissue of the coral animal host can deviate strongly from the ambient light field on a coral reef and that of artificial light sources used in lab studies on coral photobiology. Here, we used a novel approach involving light microsensor measurements and a programmable light engine to reconstruct the spectral light field that Symbiodinium is exposed to inside the coral host and the light field of a conventional halogen lamp in a comparative study of Symbiodinium photobiology. We found that extracellular gross photosynthetic O2 evolution was unchanged under different spectral illumination, while the more red-weighted halogen lamp spectrum decreased PSII electron transport rates and there was a trend towards increased light-enhanced dark respiration rates under excess irradiance. The approach provided here allows for reconstructing and comparing intra-tissue coral light fields and other complex spectral compositions of incident irradiance. This novel combination of sensor technologies provides a framework to studying the influence of macro- and microscale optics on Symbiodinium photobiology with unprecedented spectral resolution.
Richier, S., Achterberg, E.P., Dumousseaud, C., Poulton, A.J., Suggett, D.J., Tyrrell, T., Zubkov, M.V. & Moore, C.M. 2014, 'Phytoplankton responses and associated carbon cycling during shipboard carbonate chemistry manipulation experiments conducted around Northwest European shelf seas', Biogeosciences, vol. 11, no. 17, pp. 4733-4752.
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&copy; 2014 Author(s). The ongoing oceanic uptake of anthropogenic carbon dioxide (CO2) is significantly altering the carbonate chemistry of seawater, a phenomenon referred to as ocean acidification. Experimental manipulations have been increasingly used to gauge how continued ocean acidification will potentially impact marine ecosystems and their associated biogeochemical cycles in the future; however, results amongst studies, particularly when performed on natural communities, are highly variable, which may reflect community/environment-specific responses or inconsistencies in experimental approach. To investigate the potential for identification of more generic responses and greater experimentally reproducibility, we devised and implemented a series (n = 8) of short-term (2-4 days) multi-level (4 conditions) carbonate chemistry/nutrient manipulation experiments on a range of natural microbial communities sampled in Northwest European shelf seas. Carbonate chemistry manipulations and resulting biological responses were found to be highly reproducible within individual experiments and to a lesser extent between geographically separated experiments. Statistically robust reproducible physiological responses of phytoplankton to increasing pCO2, characterised by a suppression of net growth for small-sized cells (<10 m), were observed in the majority of the experiments, irrespective of natural or manipulated nutrient status. Remaining between-experiment variability was potentially linked to initial community structure and/or other site-specific environmental factors. Analysis of carbon cycling within the experiments revealed the expected increased sensitivity of carbonate chemistry to biological processes at higher pCO2and hence lower buffer capacity. The results thus emphasise how biogeochemical feedbacks may be altered in the future ocean.
Poulton, A.J., Stinchcombe, M.C., Achterberg, E.P., Bakker, D.C.E., Dumousseaud, C., Lawson, H.E., Lee, G.A., Richier, S., Suggett, D.J. & Young, J.R. 2014, 'Coccolithophores on the north-west European shelf: Calcification rates and environmental controls', Biogeosciences, vol. 11, no. 14, pp. 3919-3940.
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Coccolithophores are a key functional group in terms of the pelagic production of calcium carbonate (calcite), although their contribution to shelf sea biogeochemistry, and how this relates to environmental conditions, is poorly constrained. Measurements of calcite production (CP) and coccolithophore abundance were made on the north-west European shelf to examine trends in coccolithophore calcification along natural gradients of carbonate chemistry, macronutrient availability and plankton composition. Similar measurements were also made in three bioassay experiments where nutrient (nitrate, phosphate) and pCO2 levels were manipulated. Nanoflagellates (< 10) dominated chlorophyll biomass and primary production (PP) at all but one sampling site, with CP ranging from 0.6 to 9.6 mmol Cm-2 d-1. High CP and coccolithophore abundance occurred in a diatom bloom in fully mixed waters off Heligoland, but not in two distinct coccolithophore blooms in the central North Sea and Western English Channel. Coccolithophore abundance and CP showed no correlation with nutrient concentrations or ratios, while significant (p < 0.01) correlations between CP, cell-specific calcification (cell-CF) and irradiance in the water column highlighted how light availability exerts a strong control on pelagic CP. In the experimental bioassays,Emiliania-huxleyi-dominated coccolithophore communities in shelf waters (northern North Sea, Norwegian Trench) showed a strong response in terms of CP to combined nitrate and phosphate addition, mediated by changes in cell-CF and growth rates. In contrast, an offshore diverse coccolithophore community (Bay of Biscay) showed no response to nutrient addition, while light availability or mortality may have been more important in controlling this community. Sharp decreases in pH and a rough halving of calcite saturation states in the bioassay experiments led to decreased CP in the Bay of Biscay and northern North Sea, but not the Norwegian Trench. These decrease...
Wu, Y., Jeans, J., Suggett, D.J., Finkel, Z.V. & Campbell, D.A. 2014, 'Large centric diatoms allocate more cellular nitrogen to photosynthesis to counter slower RUBISCO turnover rates', Frontiers in Marine Science, vol. 1, no. DEC.
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&copy; 2014 Wu, Jeans, Suggett, Finkel and Campbell.Diatoms contribute ~40% of primary production in the modern ocean and encompass the largest cell size range of any phytoplankton group. Diatom cell size influences their nutrient uptake, photosynthetic light capture, carbon export efficiency, and growth responses to increasing pCO2. We therefore examined nitrogen resource allocations to the key protein complexes mediating photosynthesis across six marine centric diatoms, spanning 5 orders of magnitude in cell volume, under past, current and predicted future pCO2 levels, in balanced growth under nitrogen repletion. Membrane bound photosynthetic protein concentrations declined with cell volume in parallel with cellular concentrations of total protein, total nitrogen and chlorophyll. Larger diatom species, however, allocated a greater fraction (by 3.5-fold) of their total cellular nitrogen to the soluble Ribulose-1,5-bisphosphate Carboxylase Oxygenase (RUBISCO) carbon fixation complex than did smaller species. Carbon assimilation per unit of RUBISCO large subunit (C RbcL-1 s-1) decreased with cell volume, from ~8 to ~2 C RbcL-1 s-1 from the smallest to the largest cells. Whilst a higher allocation of cellular nitrogen to RUBISCO in larger cells increases the burden upon their nitrogen metabolism, the higher RUBISCO allocation buffers their lower achieved RUBISCO turnover rate to enable larger diatoms to maintain carbon assimilation rates per total protein comparable to small diatoms. Individual species responded to increased pCO2, but cell size effects outweigh pCO2 responses across the diatom species size range examined. In large diatoms a higher nitrogen cost for RUBISCO exacerbates the higher nitrogen requirements associated with light absorption, so the metabolic cost to maintain photosynthesis is a cell size-dependent trait.
Brodie, J., Williamson, C.J., Smale, D., Kamenos, K.A., Mieszkowska, N., Santos, R., Cunliffe, M., Steinke, M., Yesson, C., Anderson, K.M., Asnaghi, V., Brownlee C, Burdett, H.L., Burrows, M.T., Collins, S., Donahue, P.J.C., Harvey, B., Foggo, A., Noisette, F., Nunes, J., Ragazzola, F., Raven, J.A., Schmidt, D.N., Suggett, D.J., Teichberg, M. & Hall-Spencer, J.M. 2014, 'The future of the northeast Atlantic benthic flora in a high CO2 world', Ecology & Evolution, vol. 4, no. 13, pp. 2787-2798.
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Seaweed and seagrass communities in the northeast Atlantic have been profoundly impacted by humans, and the rate of change is accelerating rapidly due to runaway CO2 emissions and mounting pressures on coastlines associated with human population growth and increased consumption of finite resources. Here, we predict how rapid warming and acidification are likely to affect benthic flora and coastal ecosystems of the northeast Atlantic in this century, based on global evidence from the literature as interpreted by the collective knowledge of the authorship. We predict that warming will kill off kelp forests in the south and that ocean acidification will remove maerl habitat in the north. Seagrasses will proliferate, and associated epiphytes switch from calcified algae to diatoms and filamentous species. Invasive species will thrive in niches liberated by loss of native species and spread via exponential development of artificial marine structures. Combined impacts of seawater warming, ocean acidification, and increased storminess may replace structurally diverse seaweed canopies, with associated calcified and noncalcified flora, with simple habitats dominated by noncalcified, turf-forming seaweeds.
Brading, P., Warner, M.E., Smith, D.J. & Suggett, D.J. 2013, 'Contrasting modes of inorganic carbon acquisition amongst Symbiodinium (Dinophyceae) phylotypes', New Phytologist, vol. 200, no. 2, pp. 432-442.
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Growing concerns over ocean acidification have highlighted the need to critically understand inorganic carbon acquisition and utilization in marine microalgae. Here, we contrast these characteristics for the first time between two genetically distinct di
Ye, Z., Suggett, D.J., Robakowski, P. & Kang, H. 2013, 'A mechanistic model for the photosynthesis-light response based on the photosynthetic electron transport of photosystem II in C3 and C4 species', New Phytologist, vol. 199, no. 1, pp. 110-120.
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A new mechanistic model of the photosynthesis-light response is developed based on photosynthetic electron transport via photosystem II (PSII) to specifically describe light-harvesting characteristics and associated biophysical parameters of photosynthet
Suggett, D.J., Dong, L.F., Lawson, T., Lawrenz, E., Torres, L. & Smith, D.J. 2013, 'Light availability determines susceptibility of reef building corals to ocean acidification', Coral Reefs, vol. 32, no. 2, pp. 327-337.
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Elevated seawater pCO(2), and in turn ocean acidification (OA), is now widely acknowledged to reduce calcification and growth of reef building corals. As with other environmental factors (e.g., temperature and nutrients), light availability fundamentally
Krug, L.A., Gherardi, D.F., Stech, J.L., Leão, Z.M., Kikuchi, R.K., Junior, E.R. & Suggett, D.J. 2013, 'The construction of causal networks to estimate coral bleaching intensity', Environmental Modelling & Software, vol. 42, no. 1, pp. 157-167.
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Current metrics for predicting bleaching episodes, e.g. NOAA's Coral Reef Watch Program, do not seem to apply well to Brazil's marginal reefs located in Bahia state and alternative predictive approaches must be sought for effective long term management.
Lawrenz, E., Silsbe, G., Capuzzo, E., Ylostalo, P., Forster, R.M., Simis, S.G., Prasil, O., Kromkamp, J.C., Hickman, A.E., Moore, C.M., Forget, M., Geider, R.J. & Suggett, D.J. 2013, 'Predicting the electron requirement for carbon fixation in seas and oceans', Plos One, vol. 8, no. 3, pp. 0-0.
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Marine phytoplankton account for about 50% of all global net primary productivity (NPP). Active fluorometry, mainly Fast Repetition Rate fluorometry (FRRf), has been advocated as means of providing high resolution estimates of NPP. However, not measuring
Ye, Z., Robakowski, P. & Suggett, D.J. 2013, 'A mechanistic model for the light response of photosynthetic electron transport rate based on light harvesting properties of photosynthetic pigment molecules', Planta, vol. 237, no. 3, pp. 837-847.
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Models describing the light response of photosynthetic electron transport rate (ETR) are routinely used to determine how light absorption influences energy, reducing power and yields of primary productivity; however, no single model is currently able to
McGinley, M.P., Suggett, D.J. & Warner, M.E. 2013, 'Transcript patterns of chloroplast-encoded genes in cultured Symbiodinium spp. (Dinophyceae): testing the influence of a light shift and diel periodicity', Journal of Phycology, vol. 49, no. 4, pp. 709-718.
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Microalgae possess numerous cellular mechanisms specifically employed for acclimating the photosynthetic pathways to changes in the physical environment. Despite the importance of coral-dinoflagellate symbioses, little focus has been given as to how the symbiotic algae (Symbiodinium spp.) regulate the expression of their photosynthetic genes. This study used real-time PCR to investigate the transcript abundance of the plastid-encoded genes, psbA (encoding the D1 protein of photosystem II) and psaA (encoding the P700 protein in photosystem I), within the cultured Symbiodinium ITS-2 (internal transcribed spacer region) types A20 and A13. Transcript abundance was monitored during a low to high-light shift, as well as over a full diel light cycle. In addition, psaA was characterized in three isolates (A20, A13, and D4-5) and noted as another example of a dinoflagellate plastid gene encoded on a minicircle. In general, the overall incongruence of transcript patterns for both psbA and psaA between the Symbiodinium isolates and other models of transcriptionally controlled chloroplast gene expression (e.g., Pisum sativum [pea], Sinapis alba [mustard seedling], and Synechocystis sp. PCC 6803 [cyanobacteria]) suggests that Symbiodinium is reliant on posttranscriptional mechanisms for homeostatic regulation of its photosynthetic proteins.
Exton, D.A., Suggett, D.J., McGenity, T.J. & Steinke, M. 2013, 'Chlorophyll-normalized isoprene production in laboratory cultures of marine microalgae and implications for global models', Limnology and Oceanography, vol. 58, no. 4, pp. 1301-1311.
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We used laboratory cultures of marine microalgae to investigate the effects of growth conditions and their taxonomic position on the production of isoprene, a gas that has major effects on atmospheric chemistry and provides stress tolerance to many primary producers. Isoprene was quantified from 21 microalgal strains sampled during exponential growth, using purge-and-trap pre-concentration and gas chromatography with flameionization detection. Isoprene production rates varied by two orders of magnitude between strains (0.03 1.34 mmol [g chlorophyll a]21 h21), and were positively correlated with temperature (r2 5 0.52, p , 0.001, n 5 59). Three distinct sea surface temperature (SST)dependent relationships were found between isoprene and chlorophyll a (mmol [g chlorophyll a]21 h21), an improvement in resolution over the single relationship used in previous models: for three polar strains grown at 21uC (slope 5 0.03, R2 5 0.76, p , 0.05, n 5 9), nine strains grown at 16uC (slope 5 0.24, R2 5 0.43, p , 0.05, n 5 27 with Dunaliella tertiolecta excluded), and eight strains grown at 26uC (slope 5 0.39, R2 5 0.15, p , 0.05, n 5 24). We then used a simple model that applied the SSTdependent nature of isoprene production to three representative bioregions for the growth temperatures used in this study. This approach yielded an estimate of global marine isoprene production that was 51% higher than previous attempts using an SST-independent single relationship. Taking into account the effect of temperature therefore potentially allows more precise modeling of marine isoprene production, and suggests that increasing the SST-based resolution of data beyond the three groups used here could further improve future modeling simulations.
Suggett, D.J., Dong, L.F., Lawson, T., Lawrenz, E., Torres, L. & Smith, D.J. 2013, 'Erratum to: Light availability determines susceptibility of reef building corals to ocean acidification (Coral Reefs, 10.1007/s00338-012-0996-7)', Coral Reefs, vol. 32, no. 2, p. 339.
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Suggett, D.J., Hall-Spencer, J.M., Rodolfo-Metalpa, R., Boatman, T.G., Payton, R., Pettay, D.T., Johnson, V.R., Warner, M.E. & Lawson, T. 2012, 'Sea anemones may thrive in a high CO2 world', Global Change Biology, vol. 18, no. 10, pp. 3015-3025.
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Increased seawater pCO(2), and in turn ocean acidification (OA), is predicted to profoundly impact marine ecosystem diversity and function this century. Much research has already focussed on calcifying reef-forming corals (Class: Anthozoa) that appear pa
Suggett, D.J., Kikuchi, R.K., Oliveira, M.D., Spano, S., Carvalho, R. & Smith, D.J. 2012, 'Photobiology of corals from Brazil's near-shore marginal reefs of Abrolhos', Marine Biology, vol. 159, no. 7, pp. 1461-1473.
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Coral communities were examined from highly turbid near-shore marginal reefs of Abrolhos (Brazil) to test a paradigm previously developed from observations in clear water reefs; specifically, that coral photobiological properties follow a highly conserve
Clifton, J., Etienne, M., Barnes, D.K., Barnes, R.S., Suggett, D.J. & Smith, D.J. 2012, 'Marine conservation policy in Seychelles: Current constraints and prospects for improvement', Marine Policy, vol. 36, no. 3, pp. 823-831.
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The marine assets of Seychelles are fundamental to the national economy through generating income derived from tourism and fisheries. Marine management institutions and policies have undergone radical changes since 2008, reflecting a number of drivers an
Oxborough, K., Moore, C.M., Suggett, D.J., Lawson, T., Chan, H.G. & Geider, R.J. 2012, 'Direct estimation of functional PSII reaction center concentration and PSII electron flux on a volume basis: a new approach to the analysis of Fast Repetition Rate fluorometry (FRRf) data', Limnology and Oceanography: Methods, vol. 10, pp. 142-154.
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Green, B., Suggett, D.J., Hills, A.J. & Steinke, M. 2012, 'Optimisation of a fast DMS sensor (FDS) for real time quantification of dimethyl sulfide production by algae', Biogeochemistry, vol. 110, no. 1-3, pp. 163-172.
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Production of dimethyl sulfide (DMS) from marine samples is often quantified using gas chromatography techniques. Typically, these are labour intensive and have a slow sample turnover rate. Here we demonstrate the use of a portable fast DMS sensor (FDS) that utilises the chemiluminescent reaction of DMS and ozone to measure DMS production in aqueous samples, with a maximum frequency of 10 Hz. We have developed a protocol for quantifying DMS production that removes potential signal interference from other biogenic trace gases such as isoprene (2-methyl-1,3-butadiene) and hydrogen sulfide. The detection limit was 0.89 pM (0.02 ppbv) when using a DMS standard gas mixture. The lowest DMS production rates quantified with the FDS and verified using conventional gas chromatography with flame photometric detection (GC-FPD) were around 0.01 nmol min-1. There was a strong correlation in DMS production when comparing the FDS and GC-FPD techniques with a range of marine samples (e.g., r2 = 0.94 for Emiliania huxleyi). However, the combined dataset showed the FDS measured 22% higher DMS production than the GC-FPD, with the differences in rates likely due to interfering gases, for example hydrogen sulfide and isoprene. This possible overestimation of DMS production is smaller than the two-fold difference in DMS production between day and night samples from a culture of E. huxleyi. The response time of the instrument to changes in DMS production is method dependent (e.g., geometry of incubation vessel, bubble size) and was approximately 4 min under our conditions when using a culture of E.huxleyi (800 ml) with aeration at 100 ml min-1. We suggest the FDS can reduce sample handling, is suitable for short- and long-term measurements of DMS production in algal cultures, and will widen the range of DMS research in marine environments.
Exton, D.A., Suggett, D.J., Steinke, M. & McGenity, T.J. 2012, 'Spatial and temporal variability of biogenic isoprene emissions from a temperate estuary', Global Biogeochemical Cycles, vol. 26, no. 2, pp. 1-13.
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Isoprene is important for its atmospheric impacts and the ecophysiological benefits it affords to emitting organisms; however, isoprene emissions from marine systems remain vastly understudied compared to terrestrial systems. This study investigates for the first time drivers of isoprene production in a temperate estuary, and the role this production may play in enabling organisms to tolerate the inherently wide range of environmental conditions. Intertidal sediment cores as well as high and low tide water samples were collected from four sites along the Colne Estuary, UK, every six weeks over a year. Isoprene concentrations in the water were significantly higher at low than high tide, and decreased toward the mouth of the estuary; sediment production showed no spatial variability. Diel isoprene concentration increased with light availability and decreased with tidal height; nighttime production was 79% lower than daytime production. Seasonal isoprene production and water concentrations were highest for the warmest months, with production strongly correlated with light (r2 = 0.800) and temperature (r2 = 0.752). Intertidal microphytobenthic communities were found to be the primary source of isoprene, with tidal action acting as a concentrating factor for isoprene entering the water column. Using these data we estimated an annual production rate for this estuary of 681 mmol m2 y1 . This value falls at the upper end of other marine estimates and highlights the potentially significant role of estuaries as isoprene sources. The control of estuarine isoprene production by environmental processes identified here further suggests that such emissions may be altered by future environmental change.
Smale, D., Barnes, D., Barnes, R., Smith, D. & Suggett, D.J. 2012, 'Spatial Variability In The Structure Of Intertidal Crab And Gastropod Assemblages Within The Seychelles Archipelago (indian Ocean)', Journal of Sea Research, vol. 69, no. NA, pp. 8-15.
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Tropical nearshore ecosystems represent global hotspots of marine biodiversity and endemism but are often poorly understood and impacted by human activities. The Seychelles Archipelago (Western Indian Ocean) sustains a wealth of marine life, much of which is threatened by rapid development associated with tourism and climate change. Six marine parks exist within the Archipelago, but their biodiversity value and ecological health are poorly known, especially with regards to non-fish and coral species. Here we investigate spatial patterns of littoral biodiversity on 6 islands, 5 of which were granitic and within marine parks, including the first surveys of Curieuse and Ile Cocos. Our surveys formed a nested sampling design, to facilitate an examination of variability in species richness, faunal abundance, taxonomic distinctness and assemblage composition at multiple spatial scales, from islands (>100 s km) to quadrats (metres). We identified (mostly to species) and enumerated two target taxa, brachyuran decapod crustaceans and gastropod molluscs, and recorded over 8300 individuals belonging to over 150 species. Crabs and gastropods exhibited different patterns of spatial variability, as crab assemblages were generally more distinct between islands, while gastropod assemblages were markedly variable at the smallest spatial scales of `patch and `quadrat. Intertidal biodiversity was greatest on Curieuse Island and least at Desroches, the latter was being the only coral atoll we surveyed and thereby differing in its geological and ecological context. We discuss likely drivers of these biodiversity patterns and highlight urgently-needed research directions. Our assessment of the status of poorly-known invertebrate assemblages across the Seychelles will complement more extensive surveys of coral and fish assemblages and, in doing so, provide a useful baseline for monitoring the effects of key stressors in the region, such as coastal development and climae change.
Mansell, P.J., Suggett, D.J. & Smith, D.J. 2012, 'Management of marine resources; Combining industry and research', Journal of the Marine Biological Association of the United Kingdom, vol. 92, no. 4, pp. 643-646.
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Steinke, M., Brading, P., Kerrison, P., Warner, M.E. & Suggett, D.J. 2011, 'Concentrations of dimethylsulfoniopropionate and dimethyl sulfide are strain-specific in symbiotic dinoflagellates (Symbiodinium sp., Dinophyceae)', Journal Of Phycology, vol. 47, no. 4, pp. 775-783.
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Dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP) are sulfur compounds that may function as antioxidants in algae. Symbiotic dinoflagellates of the genus Symbiodinium show strain-specific differences in their susceptibility to temperature-induced oxidative stress and have been shown to contain high concentrations of DMSP. We investigated continuous cultures of four strains from distinct phylotypes (A1, A13, A2, and B1) that can be characterized by differential thermal tolerances. We hypothesized that strains with high thermal tolerance have higher concentrations of DMSP and DMS in comparison to strains with low thermal tolerance. DMSP concentrations were strain-specific with highest concentrations occurring in A1 (225 +/- 3.5 mmol . L(-1) cell volume [CV]) and lowest in A2 (158 +/- 3.8 mmol L) 1 CV). Both strains have high thermal tolerance. Strains with low thermal tolerance (A13 and B1) showed DMSP concentrations in between these extremes (194 +/- 19.0 and 160 +/- 6.1 mmol L(-1) CV, respectively). DMS data further confirmed this general pattern with high DMS concentrations in A1 and A13 (4.1 +/- 1.22 and 2.1 +/- 0.37 mmol . L(-1) CV, respectively) and low DMS concentrations in A2 and B1 (0.3 +/- 0.06 and 0.5 +/- 0.22 mmol . L(-1) CV, respectively). Hence, the strain-specific differences in DMSP and DMS concentrations did not match the different abilities of the four phylotypes to withstand thermal stress. Future work should quantify the possible dynamics in DMSP and DMS concentrations during periods of high oxidative stress in Symbiodinium sp. and address the role of these antioxidants in zooxanthellate cnidarians.
Brading, P., Warner, M.E., Davey, P., Smith, D.J., Achterberg, E.P. & Suggett, D.J. 2011, 'Differential effects of ocean acidification on growth and photosynthesis among phylotypes of Symbiodinium (Dinophyceae)', Limnology And Oceanography, vol. 56, no. 3, pp. 927-938.
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We investigated the effect of elevated partial pressure of CO2 (pCO(2)) on the photosynthesis and growth of four phylotypes (ITS2 types A1, A13, A2, and B1) from the genus Symbiodinium, a diverse dinoflagellate group that is important, both free-living a
Suggett, D.J. & Smith, D.J. 2011, 'Interpreting the sign of coral bleaching as friend vs. foe', Global Change Biology, vol. 17, no. 1, pp. 45-55.
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Coral bleaching is a major concern to researchers, conservationists and the general public worldwide. To date, much of the high profile attention for bleaching has coincided with major environmental impacts and for many the term coral bleaching is synonymously associated with coral mortality (so-called `lethal bleaching episodes). While this synonymous association has undoubtedly been key in raising public support, it carries unfair representation: nonlethal bleaching is, and always has been, a phenomenon that effectively occurs regularly in nature as corals acclimatize to regular periodic changes in growth environment (days, seasons etc). In addition, corals can exhibit sublethal bleaching during extreme environmental conditions whereby mortality does not occur and corals can potentially subsequently recover once ambient environmental conditions return. Perhaps not surprisingly it is the frequency and extent of these non and sublethal processes that yield key evidence as to how coral species and reef systems will likely withstand environmental and thus climatic change. Observations of non and sublethal bleaching (and subsequent recovery) are arguably not as readily reported as those of lethal bleaching since (1) the convenient tools used to quantify bleaching yield major ambiguity (and hence high potential for misidentification) as to the severity of bleaching; and (2) lethal bleaching events inevitably receive higher profile (media) attention and so are more readily reported. Under-representation of non and sublethal bleaching signs may over-classify the severity of bleaching, under-estimate the potential resilience of reefs against environmental change, and thus ultimately limit (if not depreciate) the validity and effectiveness of reef management policies and practices. While bleaching induced coral mortality must remain our key concern it must be better placed within the context of bleaching signs that do not result in a long-term loss of reefviability.
Kerrison, P., Hall-Spencer, J.M., Suggett, D.J., Hepburn, L.J. & Steinke, M. 2011, 'Assessment of pH variability at a coastal CO2 vent for ocean acidification studies', Estuarine Coastal And Shelf Science, vol. 94, no. 2, pp. 129-137.
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Marine environments with naturally high CO2 concentrations have become important research sites for studying the impacts of future ocean acidification on biological processes. We conducted high temporal resolution pH and temperature measurements in and around a shallow (2.5-3 m) CO2 vent site off Ischia, Italy in May and June 2008. Loggers were deployed at five stations to monitor water at both the surface and benthos. Our reference station, 500 m from the CO2 vent, had no noticeable vent influence. It had a naturally high and stable benthic pH (mean 8.16, inter-quartile range (IQ): 8.14-8.18) fluctuating with diel periodicity, presumably driven by community photosynthesis and respiration. A principal component analysis (PCA) revealed that the pH of this station was well constrained by meteorological parameters. In contrast, a station positioned within the vent zone, had a low and very variable benthic mean pH of 7.11 (IQ: 6.91-7.62) with large pH fluctuations not well constrained by a PCA. Any stations positioned within 20 m of the main vent zone had lowered pH, but suffered from abnormally large pH fluctuations making them unsuitable representatives to predict future changes to a shallow coastal environment. Between these extremes, we identified a benthic area with a lower pH of 7.84 (IQ: 7.83-7.88) that retained many of the characteristics of the reference station such as a natural diel pH periodicity and low variability. Our results indicate that a range of pH environments maybe commonplace near CO2 vents due to their characteristic acidification of benthic water over a wide area. Such environments could become invaluable natural laboratories for ocean acidification research, closely mimicking future CO2 conditions in a natural setting
Exton, D.A., Smith, D.J., McGenity, T.J., Steinke, M., Hills, A.J. & Suggett, D.J. 2010, 'Application of a Fast Isoprene Sensor (FIS) for measuring isoprene production from marine samples', Limnology And Oceanography-methods, vol. 8, pp. 185-195.
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Research into isoprene production from marine sources traditionally relies on gas chromatography techniques which are labor intensive, provide a slow sample turnover, and require significant method training. An alternative method is the use of a Fast Iso
Hennige, S.J., Smith, D.J., Walsh, S., McGinley, M.P., Warner, M.E. & Suggett, D.J. 2010, 'Acclimation and adaptation of scleractinian coral communities along environmental gradients within an Indonesian reef system', Journal Of Experimental Marine Biology And Ecology, vol. 391, no. 1-2, pp. 143-152.
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In 2007 and 2008, multiple sites were identified in the Wakatobi Marine National Park, South East Sulawesi, Indonesia, which each represented a point along a gradient of light quality, temperature and turbidity. This gradient included `optimal, intermediate and marginal sites, where conditions were close to the survival threshold limit for corals. Coral communities changed across this gradient from diverse, mixed growth form assemblages to specialised, massive growth form dominated communities. The massive coral Goniastrea aspera was the only species identified at the most marginal and optimal sites. Branching species Acropora formosa and Porites cylindrica were only identified at optimal sites. The in hospite Symbiodinium community also changed across the environmental gradient from members of the Symbiodinium clade C on optimal reefs (in branching and massive species) to clade D on marginal reefs (in massive species). Substantial variability in respiration and photosynthesis was observed in massive coral species under different environmental conditions, which suggests that all corals cannot be considered equal across environments. Studying present-day marginal environments is crucial to further understanding of future reef bio-diversity, functioning and accretion, and from work presented here, it is likely that as future climate change extends marginal reef range, branching coral diversity may decrease relative to massive, more resilient corals.
Ragni, M., Airs, R., Hennige, S.J., Suggett, D.J., Warner, M.E. & Geider, R.J. 2010, 'PSII photoinhibition and photorepair in Symbiodinium (Pyrrhophyta) differs between thermally tolerant and sensitive phylotypes', Marine Ecology Progress Series, vol. 406, pp. 57-70.
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Cnidarians containing symbiotic microalgae often inhabit highly variable light environments where successful growth requires that, during transient (potentially stressful) periods of high light (HL), the microalgal cells invest energy in photoprotection to minimise photodamage, or allow for photodamage to occur and invest in photorepair; however, the relative contribution of photoprotection and photorepair remains uncharacterised. Here we determined the light dependence of Photosystem II (PSII) photoinhibition and photorepair in 2 phylotypes of Symbiodinium displaying different susceptibilities to thermal stress. Upon exposure to photon flux densities (PFDs) >500 &micro;mol photons m2 s1 the thermally `sensitive Strain A1.1 displayed higher net photoinhibition, measured as a decrease in maximum PSII efficiency (Fv/Fm), than the thermally `tolerant Strain A1. In contrast, gross photoinhibition, assessed as the decline of Fv/Fm in the presence of an inhibitor of D1 protein synthesis, was similar in the 2 strains. Therefore, photorepair was considered to be the key mechanism minimising net photoinhibition in Strain A1. Consistent with this conclusion, the 2 strains displayed similar capacities for other mechanisms of avoiding photodamage, specifically, photochemical (qP) and non-photochemical (NPQ) excitation energy quenching. Measurements on Strain A1 grown under 2 PFDs (100 and 650 &micro;mol photons m2 s1) revealed that photoacclimation to HL involved the upregulation of qP, which minimised gross photoinhibition by maintaining PSII in a more oxidised state. We conclude that both interspecific (e.g. phylotype diversity) and intraspecific (e.g. photoacclimation state) factors affect the susceptibility of Symbiodinium to light stress.
Haapkyla, J., Seymour, A.S., Barneah, O., Brickner, I., Hennige, S., Suggett, D.J. & Smith, D. 2009, 'Association of Waminoa sp. (Acoela) with corals in the Wakatobi Marine Park, South-East Sulawesi, Indonesia', Marine Biology, vol. 156, no. 5, pp. 1021-1027.
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This is the first quantitative study on the prevalence of epizoic Waminoa sp. acoel worms and their association with corals in the Wakatobi Marine National Park (WMNP), South-East Sulawesi, Indonesia. Three replicate transects were laid on the reef crest
Hennige, S.J., Suggett, D.J., Warner, M.E., McDougall, K.E. & Smith, D.J. 2009, 'Photobiology of Symbiodinium revisited: bio-physical and bio-optical signatures', Coral Reefs, vol. 28, no. 1, pp. 179-195.
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Light is often the most abundant resource within the nutrient-poor waters surrounding coral reefs. Consequently, zooxanthellae (Symbiodinium spp.) must continually photoacclimate to optimise productivity and ensure coral success. In situ coral photobiolo
Suggett, D.J., MacIntyre, H.L., Kana, T.M. & Geider, R.J. 2009, 'Comparing electron transport with gas exchange:parameterising exchange rates between alternative photosynthetic currencies for eukaryotic phytoplankton', Aquatic Microbial Ecology, vol. 56, no. 2-3, pp. 147-162.
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Estimates of aquatic primary productivity derived from in situ active chl a fluorescence have rapidly gained popularity over the past 2 decades. This trend has been driven primarily by the need to improve upon `conventional carbon (C) uptake- or oxygen (O2) evolution-based productivity estimates that require water samples to be incubated ex situ. Unlike the conventional approaches to measuring productivity, chlorophyll fluorescence measurements inherently describe only the activity of photosystem II (PSII) in the light reactions; thus, the photosynthetic `currency of the fluorescence based approach is an electron turnover rate for PSII (ETRPSII). A photosynthetic currency of electrons has limited ecological relevance but can be converted to a currency of carbon if an `exchange rate, i.e. a value or factor of equivalence for any single time point, is applied. We used fast repetition rate fluorometry (FRRf), mass inlet membrane spectrometry (MIMS) and 14C uptake to determine ETRPSII, gross and net O2 evolution and C fixation measured simultaneously for 6 microalgal species and for different steady-state growth conditions. Quantifying the PSII reaction centre (RCII) concentration and the spectral dependency of the effective absorption cross section yielded an FRRf approach that provided a robust estimate of the ETRPSII and gross O2 evolution for all species and conditions tested; however, the ETRPSII exceeded carbon dioxide (CO2) uptake by a factor of ~5.4 to 11.6. At least 3 species exhibited substantial light-dependent O2 cycling to account for ~40 to 60% of the difference between the ETRPSII and CO2 uptake. The highly variable nature of the ETRPSII:CO2 uptake `exchange rate observed here highlights the need for future studies that rely on active fluorescence to examine aquatic productivity to focus towards a systematic description of how electrons are coupled to C fixation in nature
Bar-zeev, E., Berman-frank, I., Stambler, N., Vazquez-dominguez, E., Zohary, T., Capuzzo, E., Meeder, E., Suggett, D.J., Iluz, D., Dishon, G. & Berman, T. 2009, 'Transparent exopolymer particles (TEP) link phytoplankton and bacterial production in the Gulf of Aqaba', Aquatic Microbial Ecology, vol. 56, no. 2-3, pp. 217-225.
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Variations in transparent exopolymer particles (TEP), bacterial biomass production (BP) and primary productivity (PP) were followed over 52 h at a deep water station in the Gulf of Aqaba (Eilat, Israel) during the spring, in April 2008. About 20 h after the start of the study, there was a short (~15 h) but intense storm event that probably caused a nutrient pulse and, subsequently, a brief outgrowth of diatoms in the euphotic layer. Concentrations of TEP and BP ranged from 23 to 228 &micro;g gum xanthan equivalents l1 and from 0.2 to 0.6 &micro;g C l1 h1, respectively. Concentrations of TEP and BP were measured in unfiltered and in GF/C (1.2 &micro;m)-prefiltered samples. Most of the TEP (59 &plusmn; 21% of total TEP, mean &plusmn; SD) were in the smaller (GF/C-filtered) size fraction (0.41.2 &micro;m); however, after the crash of the diatom bloom, the majority of TEP were in the >1.2 &micro;m size fraction. In the GF/C-filtered fraction, BP averaged 59 &plusmn; 12% and 93 &plusmn; 5% of total BP in the upper water column and from 300 m, respectively. Significant correlations were observed between TEP and BP, suggesting that active heterotrophic bacteria may have been associated with these particles. During the 3 d of our study, PP and BP in the euphotic zone averaged 480 and 225 mg C m2 d1, respectively, suggesting that about half or more of the primary produced carbon was metabolized by heterotrophic bacteria in the upper water column. Coincident with strong mixing caused by the storm, TEP concentrations decreased in the surface water and increased at depth. We suggest that TEP acted to link carbon flux between the primary producers and heterotrophic bacteria, and that the downward movement of TEP from the upper water layers may be an important process in transferring organic carbon to deeper waters of the Gulf of Aquaba. Sinking TEP could provide not only organic carbon substrates for associated bacteria but also form `hot spots of elevated microbial metabolism and nutrient cycling throughout the water column.
Moore, C., Mills, M., Achterberg, E., Geider, R., Laroche, J., Lucas, M., Mcdonagh, E., Pan, X., Poulton, A., Rijkenberg, M., Suggett, D.J., Ussher, S. & Woodward, E. 2009, 'Large-scale Distribution Of Atlantic Nitrogen Fixation Controlled By Iron Availability', Nature Geoscience, vol. 2, no. 12, pp. 867-871.
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Oceanic fixed-nitrogen concentrations are controlled by the balance between nitrogen fixation and denitrification(1-4). A number of factors, including iron limitation(5-7), can restrict nitrogen fixation, introducing the potential for decoupling of nitrogen inputs and losses(2,5,8). Such decoupling could significantly affect the oceanic fixed-nitrogen inventory and consequently the biological component of ocean carbon storage and hence air-sea partitioning of carbon dioxide(2,5,8,9). However, the extent to which nutrients limit nitrogen fixation in the global ocean is uncertain. Here, we examined rates of nitrogen fixation and nutrient concentrations in the surfacewaters of the Atlantic Ocean along a north-south 10,000 km transect during October and November 2005. We show that rates of nitrogen fixation were markedly higher in the North Atlantic compared with the South Atlantic Ocean. Across the two basins, nitrogen fixation was positively correlated with dissolved iron and negatively correlated with dissolved phosphorus concentrations. We conclude that inter-basin differences in nitrogen fixation are controlled by iron supply rather than phosphorus availability. Analysis of the nutrient content of deep waters suggests that the fixed nitrogen enters North Atlantic Deep Water. Our study thus supports the suggestion that iron significantly influences nitrogen fixation(5), and that subsequent interactions with ocean circulation patterns contribute to the decoupling of nitrogen fixation and loss(2,4,8).
Acuna Alvarez, L., Exton, D., Timmis, K., Suggett, D.J. & Mcgenity, T. 2009, 'Characterization Of Marine Isoprene-degrading Communities', Environmental Microbiology, vol. 11, no. 12, pp. 3280-3291.
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P>Isoprene is a volatile and climate-altering hydrocarbon with an atmospheric concentration similar to that of methane. It is well established that marine algae produce isoprene; however, until now there was no specific information about marine isoprene sinks. Here we demonstrate isoprene consumption in samples from temperate and tropical marine and coastal environments, and furthermore show that the most rapid degradation of isoprene coincides with the highest rates of isoprene production in estuarine sediments. Isoprene-degrading enrichment cultures, analysed by denaturing gradient gel electrophoresis and 454 pyrosequencing of the 16S rRNA gene and by culturing, were generally dominated by Actinobacteria, but included other groups such as Alphaproteobacteria and Bacteroidetes, previously not known to degrade isoprene. In contrast to specialist methane-oxidizing bacteria, cultivated isoprene degraders were nutritionally versatile, and nearly all of them were able to use n-alkanes as a source of carbon and energy. We therefore tested and showed that the ubiquitous marine hydrocarbon-degrader, Alcanivorax borkumensis, could also degrade isoprene. A mixture of the isolates consumed isoprene emitted from algal cultures, confirming that isoprene can be metabolized at low, environmentally relevant concentrations, and suggesting that, in the absence of spilled petroleum hydrocarbons, algal production of isoprene could maintain viable populations of hydrocarbon-degrading microbes. This discovery of a missing marine sink for isoprene is the first step in obtaining more robust predictions of its flux, and suggests that algal-derived isoprene provides an additional source of carbon for diverse microbes in the oceans.
Suggett, D.J., Moore, C.M., Hickman, A.E. & Geider, R.J. 2009, 'Interpretation of fast repetition rate (FRR) fluorescence: signatures of phytoplankton community structure versus physiological state', Marine Ecology Progress Series, vol. 376, pp. 1-19.
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Introduction of active chlorophyll a fluorescence protocols, in particular fast repetition rate (FRR) fluorometry, to oceanography and limnology 15 yr ago has enabled rapid assessment of photosynthetic physiology in situ. The FRR protocol generates simultaneous measurements of Photosystem II (PSII) effective absorption cross sections (termed sPSII) and photochemical efficiency (termed Fv/Fm). Both Fv/Fm and sPSII measurements have been utilised to examine the effects of physiological stress on the photosynthetic apparatus of phytoplankton in an ever growing number of fluorescence-based studies. However, it is now becoming clearer that in situ values of Fv/Fm and sPSII also contain taxonomic information. Here, we present a synthesis of previously unpublished and published data, which show that Fv/Fm and sPSII vary principally with broad-scale changes in community structure. These patterns observed in situ conform to trends observed in laboratory-grown cultures of a range of phytoplankton taxa. The magnitudes of variability in Fv/Fm and sPSII driven by changes in phytoplankton community structure often exceed that induced by nutrient limitation (as determined from controlled nutrient addition experiments). An exception to this general trend occurs in high-nutrient, low-chlorophyll a (HNLC) regions, where strong phenotypic changes in Fv/Fm and sPSII have been repeatedly demonstrated on relief of iron limitation. Overall, FRR fluorescence measurements of both Fv/Fm and sPSII in natural populations represent a combination of the taxonomic `signature (values of Fv/Fm and sPSII determined by the taxa present) within the phytoplankton community that is further modified according to the (photo-) physiological status. As such, fluorescence-based investigations of mixed populations must account for potential variations in phytoplankton community structure before interpretations of physiological status are made.
Ross, O.N., Moore, C.M., Suggett, D.J., MacIntyre, H.L. & Geider, R.J. 2008, 'A model of photosynthesis and photo-protection based on reaction center damage and repair', Limnology and Oceanography, vol. 53, no. 5, pp. 1835-1852.
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Phytoplankton photosynthesis under the rapidly fluctuating irradiance which results from turbulent mixing through the vertical light gradient is poorly understood. Ship-based measurements often apply the fast repetition rate fluorescence (FRRF) technique in situ or in vivo to gauge the physiological state of the phytoplankton community and infer some of the physical properties of the water column (such as mixing time scales). We describe the development and validation of a model of photosynthetic electron turnover at photosystemII with consideration of downstream limitation, based on the redox state of photosystem II. We also include empirical formulations for slower processes such as photo-protection (from nonphotochemical quenching) and photo-inhibition. By confronting the simple model with laboratory data for Dunaliella tertiolecta, we were able to refine the model so that it faithfully produced rates of photosynthetic electron transfer determined by FRR fluorescence. Further, we were able to validate the model estimates of linear photosynthetic electron transfer rates against completely independent measurements obtained using 14C-bicarbonate assimilation in photosynthesis-light curves.
Suggett, D.J., Warner, M.E., Smith, D.J., Davey, P., Hennige, S. & Baker, N.R. 2008, 'Photosynthesis and production of hydrogen peroxide by Symbiodinium (Pyrrhophyta) phylotypes with different thermal tolerances', Journal Of Phycology, vol. 44, no. 4, pp. 948-956.
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Occurrences whereby cnidaria lose their symbiotic dinoflagellate microalgae (Symbiodinium spp.) are increasing in frequency and intensity. These socalled bleaching events are most often related to an increase in water temperature, which is thought to limit certain Symbiodinium phylotypes from effectively dissipating absorbed excitation energy that is otherwise used for photochemistry. Here, we examined photosynthetic characteristics and hydrogen peroxide (H2O2) production, a possible signal involved in bleaching, from two Symbiodinium types (a thermally ``tolerant A1 and ``sensitive B1) representative of cnidariaSymbiodinium symbioses of reef-building Caribbean corals. Under steady-state growth at 26C, a higher efficiency of PSII photochemistry, rate of electron turnover, and rate of O2 production were observed for type A1 than for B1. The two types responded very differently to a period of elevated temperature (32C): type A1 increased light-driven O2 consumption but not the amount of H2O2 produced; in contrast, type B1 increased the amount of H2O2 produced without an increase in light-driven O2 consumption. Therefore, our results are consistent with previous suggestions that the thermal tolerance of Symbiodinium is related to adaptive constraints associated with photosynthesis and that sensitive phylotypes are more prone to H2O2 production. Understanding these adaptive differences in the genus Symbiodinium will be crucial if we are to interpret the response of symbiotic associations, including reef-building corals, to environmental change.
Hennige, S.J., Smith, D.J., Perkins, R., Consalvey, M., Paterson, D.M. & Suggett, D.J. 2008, 'Photoacclimation, growth and distribution of massive coral species in clear and turbid waters', Marine Ecology Progress Series, vol. 369, pp. 77-88.
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Massive coral species play a key role in coral reef ecosystems, adding significantly to physical integrity, long term stability and reef biodiversity. This study coupled the assessment of the distribution and abundance of 4 dominant massive coral species, Diploastrea heliopora, Favia speciosa, F. matthaii and Porites lutea, with investigations into species-specific photoacclimatory responses within the Wakatobi Marine National Park of southeast Sulawesi, Indonesia, to determine the potential of photoacclimation to be a driver of biological success. For this, rapid light curves using pulse amplitude modulated (PAM) chlorophyll a fluorescence techniques were employed with additional manipulations to circumvent differences of light quality and absorption between species and across environmental gradients. P. lutea was examined over a range of depths and sites to determine patterns of photoacclimation, and all 4 species were assessed at a single depth between sites for which long-term data for coral community structure and growth existed. Light availability was more highly constrained with depth than between sites; consequently, photoacclimation patterns for P. lutea appeared greater with depth than across environmental gradients. All 4 species were found to differentially modify the extent of non-photochemical quenching to maintain a constant photochemical operating efficiency (qP). Therefore, our results suggest that these massive corals photoacclimate to ensure a constant light-dependent rate of reduction of the plastoquinone pool across growth environments.
Prasil, O., Suggett, D.J., Cullen, J.J., Babin, M. & Govindjee, D. 2008, 'Aquafluo 2007: chlorophyll fluorescence in aquatic sciences, an international conference held in Nové Hrady', Photosynthesis Research, vol. 95, no. 1, pp. 111-115.
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Suggett, D.J., Le Floc'h, E., Harris, G.N., Leonardos, N. & Geider, R.J. 2007, 'Different strategies of photoacclimation by two strains of Emiliania huxleyi (Haptophyta)', Journal Of Phycology, vol. 43, no. 6, pp. 1209-1222.
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Photoacclimation involves the modification of components of the light and dark reactions to optimize photosynthesis following changes in available light. All of the energy required for photosynthesis comes from linear electron transport through PSII and
Suggett, D.J., Maberly, S.C. & Geider, R.J. 2006, 'Gross photosynthesis and lake community metabolism during the spring phytoplankton bloom', Limnology And Oceanography, vol. 51, no. 5, pp. 2064-2076.
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Daily productivity determinations of linear photosynthetic electron transfer and of net and gross inorganic CO2 uptake were determined in situ throughout a 6-week sampling period of the spring phytoplankton bloom in Esthwaite Water in the English Lake Di
Moore, C.M., Suggett, D.J., Hickman, A.E., Kim, Y., Tweddle, J.F., Sharples, J., Geider, R.J. & Holligan, P.M. 2006, 'Phytoplankton photoacclimation and photoadaptation in response to environmental gradients in a shelf sea', Limnology And Oceanography, vol. 51, no. 2, pp. 936-949.
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Variability in the photosynthetic performance of natural phytoplankton communities, due to both taxonomic composition and the physiological acclimation of these taxa to environmental conditions, was assessed at contrasting sites within a temperate shelf
Suggett, D.J., Moore, C.M., Maranon, E., Omachi, C., Varela, R.A., Aiken, J. & Holligan, P.M. 2006, 'Photosynthetic electron turnover in the tropical and subtropical Atlantic Ocean', Deep Sea Research Part II: Topical Studies in Oceanography, vol. 53, no. 14-16, pp. 1573-1592.
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Photosynthetic electron transport directly generates the energy required for carbon fixation and thus underlies the aerobic metabolism of aquatic systems. We determined photosynthetic electron turnover rates, ETRs, from ca. 100 FRR fluorescence water-column profiles throughout the subtropical and tropical Atlantic during six Atlantic Meridional Transect cruises (AMT 6, MayJune 1998, to AMT 11, SeptemberOctober 2000). Each FRR fluorescence profile yielded a water-column ETR-light response from which the maximum electron turnover rate (ETRRCIImax), effective absorption (s PSII) and light saturation parameter (E k) specific to the concentration of photosystem II reaction centres (RCIIs) were calculated. ETRRCIImax and E k increased whilst s PSII decreased with mixed-layer depth and the daily integrated photosynthetically active photon flux when all provinces were considered together. These trends suggested that variability in maximum ETR can be partly attributed to changes in effective absorption. Independent bio-optical measurements taken during AMT 11 demonstrated that s PSII variability reflects taxonomic and physiological differences in the phytoplankton communities. ETRRCIImax and Ek, but not sPSII, remained correlated with mixed-layer depth and daily integrated photosynthetically active photon flux when data from each oceanic province were considered separately, indicating a decoupling of electron turnover and carbon fixation rates within each province. Comparison of maximum ETRs with 14C-based measurements of Pmax further suggests that light absorption and C fixation are coupled to differing extents for the various oligotrophic Atlantic provinces. We explore the importance of quantifying RCII concentration for determination of ETRs and interpretation of ETR-C fixation coupling.
Smith, D.J., Suggett, D.J. & Baker, N.R. 2005, 'Is photoinhibition of zooxanthellae photosynthesis the primary cause of thermal bleaching in corals?', Global Change Biology, vol. 11, no. 1, pp. 1-11.
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The bleaching of corals in response to increases in temperature has resulted in significant coral reef degradation in many tropical marine ecosystems. This bleaching has frequently been attributed to photoinhibition of photosynthetic electron transport a
Macintyre, H., Lomas, M., Cornwell, J., Suggett, D.J., Gobler, C., Koch, E. & Kana, T. 2004, 'Mediation Of Benthic-pelagic Coupling By Microphytobenthos: An Energy- And Material-based Model For Initiation Of Blooms Of Aureococcus Anophagefferens', Harmful Algae, vol. 3, no. 4, pp. 403-437.
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We present a conceptual model for initiation of blooms of the estuarine brown-tide pelagophyte Aureococcus anophagefferens. The model is based on the observation that in addition to its well-documented stimulation by organic nutrients, Aureococcus is pie
Suggett, D.J., MacIntyre, H.L. & Geider, R.J. 2004, 'Evaluation of biophysical and optical determinations of light absorption by photosystem II in phytoplankton', Limnology And Oceanography-methods, vol. 2, pp. 316-332.
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Fast repetition rate (FRR) fluorescence can provide highly resolved estimates of light absorption by photosystem II ( PSII), a variable that is critical to bio-optical determinations of phytoplankton productivity. We compared estimates of chlorophyll a -
Davey, M.S., Suggett, D.J., Geider, R.J. & Taylor, A.R. 2003, 'Phytoplankton plasma membrane redox activity: Effect of iron limitation and interaction with photosynthesis', Journal Of Phycology, vol. 39, no. 6, pp. 1132-1144.
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Phytoplankton plasma membrane electron transport activity was determined by monitoring the reduction of the impermeant artificial electron acceptor ferricyanide in a range of diatoms. The results revealed that constitutive plasma membrane electron transp
Suggett, D.J., Oxborough, K., Baker, N., Macintyre, H., Kana, T. & Geider, R. 2003, 'Fast Repetition Rate And Pulse Amplitude Modulation Chlorophyll A Fluorescence Measurements For Assessment Of Photosynthetic Electron Transport In Marine Phytoplankton', European Journal Of Phycology, vol. 38, no. 4, pp. 371-384.
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Pulse amplitude modulation (PAM) and fast repetition rate (FRR) fluorescence are currently used to estimate photosynthetic quantum yields and photosynthetic rates in aquatic systems. Here we compare simultaneous measurements of the photochemical efficien
Moore, C.M., Suggett, D.J., Holligan, P.M., Sharples, J., Abraham, E.R., Lucas, M.I., Rippeth, T., Fisher, N.R., Simpson, J.H. & Hydes, D. 2003, 'Physical controls on phytoplankton physiology and production at a shelf sea front: a fast repetition-rate fluorometer based field study', Marine Ecology Progress Series, vol. 259, pp. 29-45.
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Observations of phytoplankton physiology collected using a fast repetition-rate fluorometer (FRRF) in the vicinity of a shelf-sea tidal-mixing front are presented. These data are combined with more traditional 14C-based measurements and observations of environmental parameters, including estimates of turbulent dissipation rates, in order to investigate the influence of physical forcing on the productivity of the system. Low nutrient concentrations on the stratified side of the front result in a reduction of photosynthetic efficiency. Conversely, the high degree of vertical mixing on the mixed side of the front constrains the ability of phytoplankton to adjust their photosynthetic apparatus to the ambient irradiance field. Redistribution of phytoplankton biomass and variations in physiological parameters also result from the spring-neap tidal cycle. FRRF- and 14C-derived physiological measurements are compared in the context of environmental gradients in the region. A strong correlation was found between independently measured functional absorption cross-sections (sPSII) and maximal photosynthetic rates (P*max). Such a relationship was unlikely to have been causative and may have resulted from shifts in the balance between light-harvesting and carbon fixation across the front. The association of changes in P*max with variations in sPSII provided the basis for the development of an empirical model, specific to the system and time of study, which utilised FRRF data to extrapolate between primary productivity rates measured at fixed sites. When applied to high resolution cross-frontal data, the model suggested small-scale variations in productivity related to both spatial and temporal physical forcing including the spring-neap cycle.
Suggett, D.J., Kraay, G., Holligan, P., Davey, M., Aiken, J. & Geider, R. 2001, 'Assessment of photosynthesis in a spring cyanobacterial bloom by use of a fast repetition rate fluorometer', Limnology And Oceanography, vol. 46, no. 4, pp. 802-810.
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Estimates of gross primary production (GPP) based on fast repetition rate fluorometer (FRRF) measurements were compared with independent C-14 and O-2 at three stations during a spring bloom in the North Atlantic. A photosynthesis versus irradiance (P-E)
Gibb, S.W., Barlow, R.G., Cummings, D.G., Rees, N.W., Trees, C.C., Holligan, P. & Suggett, D. 2000, 'Surface phytoplankton pigment distributions in the Atlantic Ocean: An assessment of basin scale variability between 50°N and 50°S', Progress in Oceanography, vol. 45, no. 3-4, pp. 339-368.
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We present an overview of the spatial distributions of phytoplankton pigments along transects between the UK and the Falkland Islands. These studies, undertaken as a component of the UK Atlantic Meridional Transect (AMT) programme, provided the first post-launch validation data for the NASA SeaWiFS satellite. Pigment data are used to characterise basin-scale variations in phytoplankton biomass and community composition over 100&deg;of latitude, and to compliment the definition of hydrographic oceanic provinces. A summary of the key pigment characteristics of each province is presented. Concentrations of total chlorophyll a (totCHLa = chlorophyll a, CHLa + divinyl CHLa, dvCHLa) were greatest in high latitude temperate waters (>37&deg;N and >35&deg;S), and in the Canary Current Upwelling system. In these regions, the total carotenoid (totCAR) budget was dominated by photosynthetic carotenoids (PSCs). High accessory pigment diversity was observed of which fucoxanthin (FUC), 19'-hexanoyloxyfucoxanthin (HEX), and diadinoxanthin (DIAD) were most abundant, indicating proliferation of large eukaryotes and nanoflagellates. In contrast, tropical and sub-tropical waters exhibited concentrations of totCHLa below 500 ng l-1, with the North Atlantic Sub-tropical East gyre (NASE, 26.7-35&deg;N), South Equatorial Current (SeqC, 7-14.6&deg;S) and South Atlantic tropical Gyre (SATG, 14.6-26&deg;S) characterised by totCHLa of <100 ng-1. These waters exhibited relatively limited pigment diversity, and the totCAR budget was dominated by photoprotecting pigments (PPCs) of which zeaxanthin (ZEA), a marker of prokaryotes (cyanobacteria and prochlorophytes), was most abundant. DvCHLa, a marker of prochlorophytes was detected in waters at temperatures >15&deg;C, and between the extremes of 48&deg;N and 42&deg;S. DvCHLa accounted for up to two-thirds of totCHLa in oligotrophic provinces demonstrating the importance of prochlorophytes to oceanic biomass. Overall, HEX was the dominant PSC, contributing up to 75% of totCAR. HEX...