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Dr Simon Mitrovic


I have  dual roles as a Principal Research Scientist with the NSW DPI Water and as a Senior Lecturer in the Applied Ecology Team of the School of Life Sciences. As an applied scientist focusing on freshwater ecology, environmental flows and plant ecotoxicology part of my role with DPI Water is to ensure that students are exposed to industry related issues and undertake research relevant to industry needs. In this way research students develop skills to be placed into government and industry positions. 


Scientific Committees and editorial boards

  • Core member of Applied Ecology Team
  • Associate Editor for journal Marine and Freshwater Research
  • Member Cold Water Pollution Interagency Committee
  • Member of the NSW State Algal Advisory Group
  • Member eWater Cooperative Research Centre – Project F1 – Impacts of constituents on in-stream processes and food webs
  • Research Affiliate with National University of Singapore (NUS) Raffles Museum of Biodiversity and Research

Professional society memberships

  • International Society for Theoretical and Applied Limnology (SIL)
  • Association of Scientists in Limnology and Oceanography (ASLO)
  • Australian Society for Limnology (ASL)
  • Society for Environmental Toxicology and Chemistry (SETAC)

International Visiting Expert

  • National University of Singapore (NUS) – Biodiversity group. Invited as a phytoplankton expert to consult on program development and sampling design and to develop their skills.
  • Training courses and publication of methods and taxonomy guide for National University of Singapore (NUS).

Image of Simon Mitrovic
Senior Lecturer, School of Life Sciences

Research Interests

  • Freshwater phytoplankton ecology
  • Environmental flows, dissolved organic carbon delivery to rivers and estuaries and ecosystem responses.
  • Cyanobacterial ecology,
  • Harmful algal ecology and factors influencing toxin regulation (marine and freshwater),
  • Benthic algal ecology,
  • Fate and toxicity of algal toxins,
  • Plant ecotoxicology,

Can supervise: Yes

Graduated Honours students

  1. Alec Davie (2005) Nutrients as factors causing diatom blooms in the Hunter River, NSW, UTS. (emplyed by WaterNSW)
  2. James Hitchcock (2005-06) Effects of environmental flow delivery of carbon on productivity in the Hunter estuary, UTS. (employed by DPI Water)
  3. Daniela Cortez (2009-2010) Longitudinal trends in water quality and macroinvertebrates - Testing the serial discontinuity concept in the Hunter Catchment, UTS.
  4. Grace Corrigan (2013) Effects of light on responses of different phytoplankton communities to nutrient amendment bioassays UTS (With Prof. David Hamilton, Waikato University NZ). (employed by consultancy)
  5. Richard Carney (2013) Bacterial community changes in response to flow events in the Hunter Estuary UTS (With Dr Justin Seymour). (currently undertaking a PhD)
  6. Steven Leahey (2013) Antimony concentrations in waters and sediments of the Bellinger Estuary (With Dr Simon Apte - CSIRO). (employed by DPI Water)
  7. Carla Thomas (2013) Effects of cyanotoxin exposure on higher plants and the synergistic impacts of other stressors (employed by EPA)

Current Honours students

  1. Ellery Johnson (2015) Allochthonous organic carbon subsidies in estuaries: Importance of inflows (With Dr Wade Hadwen - Griffith University and Dr James Hitchcock DPI Water) *
  2. Sarah Meoli (2015) Are cyanobacteria more toxic than we think? (With Dr Anne Coleville) *

Graduated Masters students

  1. Patrick Stuart (2011) Evaluation of bioretention systems in Manly catchment for water quality improvement and water re-use, UTS. (employed by Manly Council)
  2. Doug Westhorpe (2011) Influence of environmental flows in DOC transport to rivers, and roles of DOC in riverine food webs, UTS. (employed by DPI Water)

Current Masters Students

  1. Rachel Gray - Effectiveness of thermal pollution mitigation using a novel thermal curtain. (with Lorraine Hardwick PII Water and Dr Hugh Jones (OEH) *
  2. Christian Moore - Cold Water pollution in the Macquarie River and remediation using a thermal curtain (with Allan Lugg DPI Fisheries) *

Completed PhD Students

  1. Alec Davie - The influence of environmental flows on periphyton communities in the Severn River, NSW, UTS. * (employed by WaterNSW)
  2. Stefanie Mueller - Limitation of phytoplankton and sediment release of nutrients in a shallow reservoir, UTS.* (employed by UTS)
  3. James Hitchcock - The effect of environmental flows and nutrient and carbon inflows on the planktonic foodweb in the Bega River Estuary, UTS.* (employed by DPI Water)
  4. Ben Woodward – Mobilisation of carbon on soils in the Gwydir River – Griffith University. (employed by Hamburg University)
  5. Maxine Mowe - Cyanobacterial toxins in Singapore’s Reservoirs; identifying progenitor species, toxin production rates and responses to environmental variables, National University of Singapore.

Current PhD Students

  1. Ann-Marie Rohlfs - Role of tributary inflows for carbon supply in environmental flow management of the regulated Snowy Mountains Rivers, UTS (With Dr Gavin Rees CSIRO and Simon Wiliiams DPI Water). *
  2. Rebecca Herron – Algae as bioindicators of herbicide pollution in the Great Barrier Reef catchments.UTS (With Dr Ben Kefford - Uni of Canberra) *
  3. Lloyd Werry - climate change effects on macroinvertebrates in the Snowy Mountains (With Dr Ben Kefford - Uni of Canberra) *
  4. Joe Pera - Carp and water quality issues - with WaterNSW (Dr Alec

Aquatic Ecology 91121

Stream and Lake Assessment 91155


Mitrovic, S.M., Hawkins, P.R., Bowling, L.C., Buckney, R.T. & Cheng, D.M.H. 2001, 'Low nitrate concentrations in a tidally mixed river coincide with replacement of chlorophytes by the cyanophyte Microcystis', INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, VOL 27, PT 2, PROCEEDINGS, pp. 924-929.

Journal articles

Mueller, S., Mitrovic, S.M. & Baldwin, D.S.B. 2016, 'Oxygen and dissolved organic carbon control release of N, P and Fe from the sediments of a shallow, polymictic lake', Journal of Soils and Sediments, vol. 16, no. 3, pp. 1109-1120.
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Purpose We examined potential causes of nutrient release from the sediments of a shallow polymictic reservoir that, unlike many other shallow lakes, had not received large amounts of nutrient loading. It was hypothesised that the sediments released greater amounts of nutrients under anoxic rather than oxic conditions and that nitrogen (N) and phosphorus (P) release was limited by the availability of different types of organic substrate. Materials and methods Sediment incubation experiments under oxic and anoxic conditions were conducted in summer and in winter. One anoxic incubation experiment with the addition of different types of dissolved organic substrate (glucose, acetate, formate and propionate) was carried out. Concentrations of nitrite and nitrate (NOx -N), ammonium (NH4 +-N), soluble reactive P (srP) and iron (Fe(II)) were monitored in the supernatant of the incubation chambers over 28 days. Thermal stratification was monitored in situ for 17 months and sediment composition was analysed. Results and discussion NOx -N concentration increased by 5.67±0.33 mg N l1 in anoxic conditions but was much lower in oxic treatments. Release of srP was low in anoxic and oxic treatments (0.004±0.001 mg P l1) but was stimulated by 0.027±0.015 mg P l1 under additions of formate. Fe(II) release was mostly stimulated by glucose additions (25.59± 4.28 mg Fe l1). P release was much lower than observed in eutrophic lakes. P release does not appear to be as a result of the reduction of Fe minerals and concurrent dissolution of orthophosphate, often reported as the most prevalent pathway for P release from anaerobic lake sediments. Conclusions Iron and P flux from lake sediments can be independent from each other and can be controlled by dissolved organic C. Further, the study confirms the role of oxygen availability in controlling nutrient release from the sediments.
Mowe, M.A.D., Abbas, F., Porojan, C., Mitrovic, S.M., Lim, R.P., Furey, A. & Yeo, D.C.J. 2016, 'Roles of nitrogen and phosphorus in growth responses and toxin production (using LC-MS/MS) of tropical Microcystis ichthyoblabe and M. flos-aquae', Journal of Applied Phycology.
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© 2015 Springer Science+Business Media Dordrecht In experiments investigating nutrient effects on tropical Microcystis, increasing nitrogen and phosphorus concentrations were found to have a significant positive effect on maximum cell yields of two strains of Microcystis ichthyoblabe (from Lower Peirce and Tengeh Reservoirs) and one strain of Microcystis flos-aquae isolated (Lower Peirce Reservoir) from Singapore. However, only increasing nitrogen concentration had a positive effect on growth rates of M. ichthyoblabe and M. flos-aquae from Lower Peirce Reservoir. MC-RR and MC-LR were produced by all three strains with MC-RR being the dominant variant. Phosphorus played an important role in MC production with increases in phosphorus from medium to high concentrations leading to decreases in MC-RR cell quotas for all three strains at the two highest nitrogen levels tested. The different growth and toxin production responses between M. ichthyoblabe strains could be due to location-specific differences.
Wood, R.J., Mitrovic, S.M., Lim, R.P. & Kefford, B.J. 2016, 'The influence of reduced light intensity on the response of benthic diatoms to herbicide exposure.', Environmental Toxicology and Chemistry, vol. 35, no. 9, pp. 2252-2260.
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Herbicide pollution events in aquatic ecosystems often co-occur with increased turbidity and reduced light intensity. It is therefore important to determine whether reduced light intensity can influence herbicide toxicity, especially to primary producers such as benthic diatoms. Benthic diatoms collected from four rivers were exposed to herbicides in 48h rapid toxicity tests under high light (100µmolm(-2) s(-1) ) and low light (20µmolm(-2) s(-1) ) intensities. The effects of two herbicides (atrazine and glyphosate) were assessed on 26 freshwater benthic diatom taxa. There was no significant interaction of light and herbicide effects at the community level or on the majority (22 of 26) of benthic diatom taxa. This indicates that low light levels will likely have only a minor influence on the response of benthic diatoms to herbicides. This article is protected by copyright. All rights reserved.
Hitchcock, J.N., Mitrovic, S.M., Hadwen, W.L., Roelke, D.L., Growns, I.O. & Rohlfs, A.M. 2016, 'Terrestrial dissolved organic carbon subsidizes estuarine zooplankton: An in situ mesocosm study', Limnology and Oceanography, vol. 61, no. 1, pp. 254-267.
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© 2016 Association for the Sciences of Limnology and Oceanography. Freshwater inflows play an important role in delivering dissolved organic carbon (DOC) to estuaries. Episodic inputs of DOC may support increased bacterial production. However, the role of DOC in supporting zooplankton production is widely debated. To evaluate this role we performed an in situ mesocosm experiment in the Bega River estuary, Australia. We added a DOC leachate derived from terrestrial vegetation to 400 L mesocosm bags as treatments of +1.5, +3, and +16 mg C L-1 and monitored changes in carbon, nitrogen, phosphorus, bacteria, chlorophyll a (Chl a), and zooplankton over 22 d. Bacterial biomass peaked at day 2 and was highest in the +16 mg C L-1 treatment. Chl a was not significantly different between treatments. Mesozooplankton was dominated by copepodites of Gladioferens pectinatus and Sulcanus conflictus between days 5-9 and by adults between days 9-15. Significantly higher numbers of copepods were present in the +16 treatment followed by the +3 mg C L-1 treatment compared with the controls. Stable carbon isotope signatures of copepods in the +16 mg C L-1 treatment were significantly different from the control and showed leachate carbon supported between 29.3% and 55.8% of copepod biomass. These results suggest that the impact of allochthonous DOC loading events on estuarine zooplankton occurs over short periods, and that the magnitude of response is, in part, controlled by the quantity of bioavailable DOC loaded to the system. Our findings underscore the importance of microbial dynamics stimulated by DOC loading events from freshwater inflows as a trophic path in estuarine food webs.
Rohlfs, A.M., Mitrovic, S.M., Williams, S., Hitchcock, J.N. & Rees, G.N. 2016, 'Dissolved organic carbon delivery from managed flow releases in a montane snowmelt river', Aquatic Sciences, pp. 1-15.
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© 2016 Springer International Publishing Managed flow releases are increasingly being utilised in the rehabilitation of regulated rivers to improve physical habitat condition and restore spatial connectivity. However, the potential for managed flow releases to influence basal resource availability to the downstream food web has received less attention. This study investigated dissolved organic carbon (DOC) delivery from managed flow releases from Jindabyne Dam and a regulated tributary to the Snowy River; a mixed rainfall-snowmelt river in south-east Australia. DOC concentration and load were monitored downstream of Jindabyne Dam during two high-flow dam releases and 2 month-long tributary releases provided by temporarily suspending tributary weir diversions. DOC chemical composition in the downstream Snowy River was characterised using fluorescence spectrophotometry. A negligible change or decrease in DOC concentration occurred at all monitored sites during both dam releases. In contrast, pulsed increases in DOC concentration concomitant with natural high-flow events were observed in the Snowy River during the tributary releases. The estimated DOC load delivered by the larger dam release increased 1.5-fold between sites 2 and 22 km downstream of the Jindabyne Dam. Reservoir release waters contained both humic-like and protein-like DOC fluorophores, whereas tributary releases contained only humic-like DOC fluorophores. Collectively, these results suggest that changes in DOC quantity and composition during managed dam releases reflect localised wetting and DOC mobilisation from the riparian zone whilst tributary releases deliver storm-associated pulses of terrestrial DOC flushed from the catchment. The unique DOC regimes associated with dam and tributary-sourced water releases may influence ecosystem functioning in the downstream river.
Wood, R.J., Mitrovic, S.M., Lim, R.P. & Kefford, B.J. 2016, 'How benthic diatoms within natural communities respond to eight common herbicides with different modes of action', SCIENCE OF THE TOTAL ENVIRONMENT, vol. 557, pp. 636-643.
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Carney, R.L., Seymour, J.R., Westhorpe, D. & Mitrovic, S.M. 2016, 'Lotic bacterioplankton and phytoplankton community changes under dissolved organic-carbon amendment: Evidence for competition for nutrients', Marine and Freshwater Research, vol. 67, no. 9, pp. 1362-1373.
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During periods of low river discharge, bacterial growth is typically limited by dissolved organic carbon (DOC) and is tightly regulated by phytoplankton production. However, import of allochthonous DOC into rivers by freshwater inflows may diminish bacterial reliance on phytoplankton-produced carbon, leading to competition for nitrogen (N) and phosphorus (P). To investigate phytoplankton-bacterial competition in response to allochthonous inputs, we conducted a mesocosm experiment, comparing microbial responses to the following two manipulation treatments: (1) addition of N and P, and (2) addition of a DOC and N and P. Measurement of chlorophyll-a estimated phytoplankton biomass and microscopic counts were performed to discriminate community change. Bacterial abundance was tracked using flow cytometry and community assemblages were characterised using automated ribosomal intergenic spacer analyses and 16S rRNA-amplicon sequencing. We found that bacterial abundance increased in the leachate addition, whereas chlorophyll-a was reduced and the bacterial community shifted to one dominated by heterotrophic genera, and autotrophic microbes including Synechococcus and Cyclotella increased significantly in the nutrient treatment. These observations indicated that DOC and nutrient inputs can lead to shifts in the competitive dynamics between bacteria and phytoplankton, reducing phytoplankton biomass, which may potentially shift the major pathway of carbon to higher trophic organisms, from the phytoplankton grazer chain to the microbial food web.
Rohlfs, A.M., Mitrovic, S.M., Williams, S. & Coleman, D. 2016, 'Can tributary in-flows improve the recovery of the dissolved organic carbon regime in a snowmelt river regulated by a large reservoir?', Marine and Freshwater Research, vol. 67, no. 9, pp. 1338-1345.
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Although tributary inputs can accelerate the recovery of many physical and chemical gradients below large reservoirs, their contribution to the dissolved organic carbon (DOC) regime in regulated rivers remains poorly studied. In some regulated tributaries, flow volumes can be manipulated, potentially influencing DOC supply to the main stem. The present study examines how tributary water diversion affects DOC supply to a snowmelt river regulated by large reservoirs. DOC concentration was measured at tributary and main stem sites, and tributary DOC export was estimated under different tributary flow-diversion scenarios. Significant, positive correlations between DOC concentration and discharge were absent directly below the dam, but were present in the unregulated tributary, and re-emerged below the tributary confluence. Irrespective of water-diversion practices, tributary in-flows reconnected the regulated main stem to a more variable DOC regime driven by catchment flushing processes. However, tributary water diversion dampened the tributary signal by reducing DOC pulse frequency and total DOC export to the regulated river. These aspects of the DOC regime may influence basal resource availability and ecosystem functioning in the regulated main stem. The present study illustrates how an ecologically valuable tributary function can be addressed and quantified to guide the management and rehabilitation of a regulated river system.
Hitchcock, J.N., Mitrovic, S.M., Hadwen, W.L., Growns, I.O. & Rohlfs, A.M. 2016, 'Zooplankton responses to freshwater inflows and organic-matter pulses in a wave-dominated estuary', Marine and Freshwater Research, vol. 67, no. 9, pp. 1374-1386.
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Freshwater inflow events play a major role in structuring estuarine zooplankton communities. Freshwater inflow events affect zooplankton directly through advective forcing and changes in salinity, and indirectly through changes to resources by the delivery of organic carbon and nutrients that can stimulate microbial and primary production. Here, we investigate changes to estuarine zooplankton assemblage structure, density and 13C stable isotopes during a period of highly variable freshwater inflow in the Bega River estuary, Australia. High inflows resulted in a reduction of salinity and a shift in the zooplankton assemblage structure from purely estuarine taxa towards freshwater taxa. The density of select genera of rotifers, cladocera and, in the upper estuary, copepods, increased following inflows, concurrent with increases in the concentration of dissolved organic carbon and bacterial biomass. Redundancy analysis found that environmental variables including discharge, dissolved organic carbon, salinity and bacterial biomass explained 66-73% of zooplankton variation. Stable isotope results indicated that all copepod and cladocera species tested were predominantly supported by allochthonous carbon from terrestrial sources. The present results have provided important evidence that freshwater inflows play a critical role in structuring zooplankton assemblages and supporting increased production through the delivery of allochthonous organic carbon.
Mitrovic, S.M. & Baldwin, D.S. 2016, 'Allochthonous dissolved organic carbon in river, lake and coastal systems: Transport, function and ecological role', Marine and Freshwater Research, vol. 67, no. 9, pp. i-iv.
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Baldwin, D.S., Colloff, M.J., Mitrovic, S.M., Bond, N.R. & Wolfenden, B. 2016, 'Restoring dissolved organic carbon subsidies from floodplains to lowland river food webs: A role for environmental flows?', Marine and Freshwater Research, vol. 67, no. 9, pp. 1387-1399.
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Environmental flows are managed events in river systems designed to enhance the ecological condition of aquatic ecosystems. Although not traditionally seen as important in lowland rivers, there is mounting evidence that terrestrial subsidies can be an important energy source in aquatic metazoan food webs. We argue that the apparent lack of importance of terrestrial subsidies to many lowland river food webs may reflect an artefact resulting from historical anthropogenic changes to lowland river-floodplain ecosystems, including the loss of lateral connectivity between rivers and their floodplains, changes in floodplain land use and carbon stores, and loss of sites of transformation within the main channel. The loss of floodplain subsidies to the main river channel can be partially redressed using environmental flows; however, this will require mimicking important aspects of natural high-flow events that have hitherto been overlooked when targeting environmental flows to a limited suite of biota. We suggest that key biotic targets for environmental flow releases may not be achievable unless river-floodplain subsidies are sufficiently restored. Environmental flows can go some way to addressing this shortfall, but only if floodplain subsidies to river channels are explicitly included in the design and management of environmental flows.
Porojan, C., Mitrovic, S.M., Yeo, D.C.J. & Furey, A. 2016, 'Overview of the potent cyanobacterial neurotoxin -methylamino-L-alanine (BMAA) and its analytical determination', Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment, vol. 33, no. 10, pp. 1570-1586.
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© 2016 Informa UK Limited, trading as Taylor & Francis Group.Blue-green algae are responsible for the production of different types of toxins which can be neurotoxic, hepatotoxic, cytotoxic and dermatotoxic and that can affect both aquatic and terrestrial life. Since its discovery the neurotoxin -methylamino-L-alanine (BMAA) has been a cause for concern, being associated with the neurodegenerative disease amyotrophic lateral sclerosis/Parkinsonism–dementia complex (ALS/PDC). The initial focus was on Guam where it was observed that a high number of people were affected by the ALS/PDC complex. Subsequently, researchers were surprised to find levels of BMAA in post mortem brains from Canadian patients who also suffered from ALS/PDC. Recent research demonstrates that BMAA has been found at different levels in the aquatic food web in the brackish waters of the Baltic Sea. There is emerging evidence to suggest that sand-borne algae from Qatar can also contain BMAA. Furthermore, there is now concern because BMAA has been found not only in warmer regions of the world but also in temperate regions like Europe. The aim of this review is to focus on the methods of extraction and analysis of the neurotoxic non-protein amino acid BMAA. We also consider the neurotoxicity, aetiology, and diverse sources and routes of exposure to BMAA. In recent years, different methods have been developed for the analysis of BMAA. Some of these use HPLC-FD, UPLC-UV, UPLC-MS and LC-MS/MS using samples that have been derivatised or underivatised. To date the LC-MS/MS approach is the most widely used analytical technique as it is the most selective and sensitive method for BMAA determination.
Mowe, M.A.D., Porojan, C., Abbas, F., Mitrovic, S.M., Lim, R.P., Furey, A. & Yeo, D.C.J. 2016, 'Corrigendum to "Rising temperatures may increase growth rates and microcystin production in tropical Microcystis species" [Harmful Algae 50 88-98]', Harmful Algae.
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Griffin, C.T., Mitrovic, S.M., Danaher, M. & Furey, A. 2015, 'Development of a fast isocratic LC-MS/MS method for the high-throughput analysis of pyrrolizidine alkaloids in Australian honey.', Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment, vol. 32, no. 2, pp. 214-228.
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Honey samples originating from Australia were purchased and analysed for targeted pyrrolizidine alkaloids (PAs) using a new and rapid isocratic LC-MS/MS method. This isocratic method was developed from, and is comparable with, a gradient elution method and resulted in no loss of sensitivity or reduction in chromatographic peak shape. Isocratic elution allows for significantly shorter run times (6 min), eliminates the requirement for column equilibration periods and, thus, has the advantage of facilitating a high-throughput analysis which is particularly important for regulatory testing laboratories. In excess of two hundred injections are possible, with this new isocratic methodology, within a 24-h period which is more than 50% improvement on all previously published methodologies. Good linear calibrations were obtained for all 10 PAs and four PA N-oxides (PANOs) in spiked honey samples (3.57-357.14 µg l(-1); R(2) 0.9987). Acceptable inter-day repeatability was achieved for the target analytes in honey with % RSD values (n = 4) less than 7.4%. Limits of detection (LOD) and limits of quantitation (LOQ) were achieved with spiked PAs and PANOs samples; giving an average LOD of 1.6 µg kg(-1) and LOQ of 5.4 µg kg(-1). This method was successfully applied to Australian and New Zealand honey samples sourced from supermarkets in Australia. Analysis showed that 41 of the 59 honey samples were contaminated by PAs with the mean total sum of PAs being 153 µg kg(-1). Echimidine and lycopsamine were predominant and found in 76% and 88%, respectively, of the positive samples. The average daily exposure, based on the results presented in this study, were 0.051 µg kg(-1) bw day(-1) for adults and 0.204 µg kg(-1) bw day(-1) for children. These results are a cause for concern when compared with the proposed European Food Safety Authority (EFSA), Committee on Toxicity (COT) and Bundesinstitut für Risikobewertung (BfR - Federal Institute of Risk Assessment Germany) maximum daily PA...
Zhao, C., Liu, C., Dai, X., Liu, T., Duan, Z., Liu, L. & Mitrovic, S.M. 2015, 'Separation of the impacts of climate change and human activity on runoff variations', Hydrological Sciences Journal, vol. 60, no. 2, pp. 234-246.
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© 2014, © 2014 IAHS.Abstract: A practical approach to separate the impact of the processes of climate change (CC) and human activities (HA) on streamflow is presented. A non-parametric Mann-Kendall-Sneyers test, combined with moving t test and Yamamoto methods, was used to recognize abrupt change points in the runoff time series to determine a baseline period. A new algorithm to separate CC and HA influence on streamflow was deduced based on the climate elasticity concept. Application to the Chao River, China, shows that CC imposed a positive impact on streamflow in this region (25%, on average), while HA exerted a continuous negative impact of –75% in the period after the 1950s. These results are of great use in understanding the variation of CC and HA impacts under different human development patterns.
Hitchcock, J.N. & Mitrovic, S.M. 2015, 'Highs and lows: The effect of differently sized freshwater inflows on estuarine carbon, nitrogen, phosphorus, bacteria and chlorophyll a dynamics', Estuarine, Coastal and Shelf Science, vol. 156, pp. 71-82.
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Freshwater inflows play a key role in the delivery of organic carbon to estuaries. However, our understanding of the dynamics between discharge and carbon globally is limited. In this study we performed a 30-month monitoring study on the Bega and Clyde River estuaries, Australia, to understand the influence that discharge had on carbon, nitrogen, phosphorus, bacteria and chlorophyll a dynamics. We hypothesised that 1) discharge would be the most important factor influencing carbon and nutrient concentrations, though during low flows chlorophyll a would also be positively related to carbon, 2) bacteria would be related to dissolved organic carbon (DOC), and chlorophyll a to temperature, nitrogen and phosphorus, and 3) that concentrations of carbon, nitrogen, phosphorus, bacterial biomass and chlorophyll a would be significantly different between large 'flood flows', smaller 'fresh flows' and base flow conditions. We found that discharge was always the most important factor influencing carbon and nutrient concentrations, and that primary production appeared to have little influence on the variation in DOC concentration even during base flow conditions. We suggest this relationship is likely due to highly episodic discharge that occurred during the study period. Bacteria were related to DOC in the lower estuary sites, but phosphorus in the upper estuary. We suggest this is likely due to the input of bioavailable carbon in the upper estuary leading bacteria to be P limited, which changes downstream to carbon limitation as DOC becomes more refractory. Chlorophyll a was positively related to temperature but not nutrients, which we suggest may be due to competition with bacteria for phosphorus in the upper estuary. Carbon, nitrogen and phosphorus concentrations were different under flood, fresh and base flow conditions, though these differences sometimes varied between estuary locations for different resources. Overall, the results demonstrate that discharge plays an im...
Zhao, C.S., Yang, S.T., Liu, C.M., Dou, T.W., Yang, Z.L., Yang, Z.Y., Liu, X.L., Xiang, H., Nie, S.Y., Zhang, J.L., Mitrovic, S.M., Yu, Q. & Lim, R.P. 2015, 'Linking hydrologic, physical and chemical habitat environments for the potential assessment of fish community rehabilitation in a developing city', Journal of Hydrology, vol. 523, pp. 384-397.
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© 2015 Elsevier B.V.Aquatic ecological rehabilitation is increasingly attracting considerable public and research attention. An effective method that requires less data and expertise would help in the assessment of rehabilitation potential and in the monitoring of rehabilitation activities as complicated theories and excessive data requirements on assemblage information make many current assessment models expensive and limit their wide use. This paper presents an assessment model for restoration potential which successfully links hydrologic, physical and chemical habitat factors to fish assemblage attributes drawn from monitoring datasets on hydrology, water quality and fish assemblages at a total of 144 sites, where 5084 fish were sampled and tested. In this model three newly developed sub-models, integrated habitat index (. IHSI), integrated ecological niche breadth (. INB) and integrated ecological niche overlap (. INO), are established to study spatial heterogeneity of the restoration potential of fish assemblages based on gradient methods of habitat suitability index and ecological niche models. To reduce uncertainties in the model, as many fish species as possible, including important native fish, were selected as dominant species with monitoring occurring over several seasons to comprehensively select key habitat factors. Furthermore, a detrended correspondence analysis (DCA) was employed prior to a canonical correspondence analysis (CCA) of the data to avoid the "arc effect" in the selection of key habitat factors. Application of the model to data collected at Jinan City, China proved effective reveals that three lower potential regions that should be targeted in future aquatic ecosystem rehabilitation programs. They were well validated by the distribution of two habitat parameters: river width and transparency. River width positively influenced and transparency negatively influenced fish assemblages. The model can be applied for monitoring the effects of...
Westhorpe, D.P., Mitrovic, S.M., Growns, I.O., Hadwen, W.L. & Rees, G.N. 2015, 'Disruption in water quality patterns along the river continuum by a large bottom release dam', AUSTRALASIAN JOURNAL OF ENVIRONMENTAL MANAGEMENT, vol. 22, no. 4, pp. 400-416.
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Mowe, M.A.D., Mitrovic, S.M., Lim, R.P., Furey, A. & Yeo, D.C.J. 2015, 'Tropical cyanobacterial blooms: a review of prevalence, problem taxa, toxins and influencing environmental factors', Journal of Limnology, vol. 73, no. 2, pp. 205-224.
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Woodward, K.B., Fellows, C.S., Mitrovic, S.M. & Sheldon, F. 2015, 'Patterns and bioavailability of soil nutrients and carbon across a gradient of inundation frequencies in a lowland river channel, Murray-Darling Basin, Australia', Agriculture, Ecosystems and Environment, vol. 205, pp. 1-8.
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© 2015 Elsevier B.V.The distribution of both carbon and nutrient stores in the landscape is not homogeneous, and is influenced by soil properties such as texture and organic content as well as spatial gradients such as inundation frequency. In this study the distribution of water extractable soil nutrients and water mobile dissolved organic carbon (DOC) and its bioavailability were investigated at specific levels along a cross-sectional gradient that extended from the baseflow level deep in the channel to the floodplain. The frequency with which these specific levels are inundated was modelled under three flow regimes to determine if flow change is likely to influence nutrient supply to the river. Soil surface litter and soil organic carbon content, DOC and SRP increased along a trajectory from the base of the channel onto the floodplain. Ammonium increased and nitrate decreased as in-channel height decreased. This reflects an increase in soil inundation frequency lower in the channel decreasing nitrification rates and increasing NO3- losses via mobilisation and denitrification. Bioavailable soil DOC (BDOC) was lowest in the most frequently inundated soils; however, overall soil BDOC did not relate to either changing soil properties or inundation frequency. There were no significant differences in nutrient and carbon supply to the river under the three modelled flow regimes (with flows extraction rules, without flow extraction rules and natural flows) explored as flow change was most marked in the channel bed region, where little organic matter was stored.
Hitchcock, J.N. & Mitrovic, S.M. 2015, 'After the flood: changing dissolved organic carbon bioavailability and bacterial growth following inflows to estuaries', Biogeochemistry, vol. 124, no. 1-3, pp. 219-233.
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&copy; 2015, Springer International Publishing Switzerland.Freshwater inflows play an important role in delivering dissolved organic carbon (DOC) to estuaries. Although considerable DOC can be delivered to estuaries during episodic inflow events, such as floods, little information exists on how the bioavailability of DOC may change during these periods. In this study we used in vitro bioassay incubation experiments to examine how bioavailability changed following inflow events in two temperate south east Australian estuaries; the agricultural Bega River and the forested Clyde River. We measured short-term (2&nbsp;days) and long-term (28&nbsp;days) bioavailable DOC (BDOC) and determined percentage bioavailability, bacterial doubling times (BTd), all with and without excess nitrogen and phosphorus to control for nutrient limitation. Our results showed BDOC varied between 0.13 and 3.62&nbsp;mg&nbsp;C&nbsp;L<sup>1</sup>, equivalent to 2.5&#8211;31&nbsp;% of initial concentrations. BTd were significantly shorter at the peak of flow and reduced as discharge returned to base flow conditions. Multiple-regression analysis showed discharge and specific ultraviolet light absorbance were the best factors for explaining variance in BDOC whilst discharge was the best factor for explaining BTd. The addition of nutrients led to significantly higher measurements of BDOC and bacteria doubling times on the Clyde River when initial phosphorus concentrations were low. These results highlight the importance of freshwater inflow events as intense moments of biogeochemical transformation in estuaries.
Carney, R.L., Mitrovic, S.M., Jeffries, T., Westhorpe, D., Curlevski, N. & Seymour, J.R. 2015, 'River bacterioplankton community responses to a high inflow event', Aquatic Microbial Ecology, vol. 75, no. 3, pp. 187-205.
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&copy; Inter-Research 2015. Microbes drive chemical cycling and productivity within river ecosystems, but their influence may shift when intense allochthonous inputs accompany high freshwater inflow (flood) events. Investigating how floods influence microbial processes is fundamentally important for our understanding of river ecology, but is generally overlooked. We analysed bacterioplankton community composition (BCC) and abundance over 4 mo following an enormous flood event in the Hunter River, Australia, that resulted in a major fish kill. Concentrations of dissolved organic carbon (DOC) and inorganic nutrients (N and P) were up to 3 times higher during the flood event compared to prior and subsequent months. Bacterial cell abundances were up to 10 times higher at impacted sites during the flood event. Using Automated Ribosomal Intergenic Spacer Analysis we found significant shifts in BCC between the flood impacted month and subsequent months (p < 0.05). Distance linear modelling indicated that DOC and dissolved N and P correlated most strongly with BCC patterns during the high inflow, whereas community dynamics correlated most strongly with nitrogen oxides and ammonium during the river's recovery phase. 16S rRNA amplicon pyrosequencing revealed that common soil-associated and facultative anaerobic genera of Proteobacteria were most dominant during the flood period, suggesting that a proportion of the bacterial community observed during this event were potentially inactive soil microbes transported into the river via terrestrial runoff. During the recovery period, Cyanobacteria and freshwater- associated genera of Actinobacteria and Proteobacteria became dominant in 16S rRNA pyrosequencing profiles. These observations indicate that allochthonous nutrients delivered via floods can significantly stimulate bacterial growth, underpinning substrate-controlled succession of bacterial communities and ultimately shaping the ecology within river ecosystems.
Mowe, M.A.D., Porojan, C., Abbas, F., Mitrovic, S.M., Lim, R.P., Furey, A. & Yeo, D.C.J. 2015, 'Rising temperatures may increase growth rates and microcystin production in tropical Microcystis species', Harmful Algae, vol. 50, pp. 88-98.
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&copy; 2015 Elsevier B.V. All rights reserved. Rising temperatures (1.4-6 &deg;C) due to climate change have been predicted to increase cyanobacterial bloom occurrences in temperate water bodies; however, the impacts of warming on tropical cyanobacterial blooms are unknown. We examined the effects of four different temperatures on the growth rates and microcystin (MC) production of five tropical Microcystis isolates (M. ichthyoblabe (two strains), M. viridis, M. flos-aquae, and M. aeruginosa). The temperature treatments are based on current temperature range in Singapore's reservoirs (27 &deg;C and 30 &deg;C), as well as projected mean (33 &deg;C) and maximum temperatures (36 &deg;C) based on tropical climate change estimates of +6 &deg;C in air temperature. Increasing temperatures did not significantly affect the maximum growth rates of most Microcystis strains. Higher growth rates were only observed in one M. ichthyoblabe strain at 33 &deg;C and M. flos-aquae at 30 &deg;C where both were isolated from the same reservoir. MC-RR and MC-LR were produced in varying amounts by all four species of Microcystis. Raised temperatures of 33 &deg;C were found to boost total MC cell quota for three Microcystis strains although further increase to 36 &deg;C led to a sharp decrease in total MC cell quota for all five Microcystis strains. Increasing temperature also led to higher MC-LR:MC-RR cell quota ratios in M. ichthyoblabe. Our study suggests that higher mean water temperatures resulting from climate change will generally not influence growth rates of Microcystis spp. in Singapore except for increases in M. ichthyoblabe strains. However, toxin cell quota may increase under moderate warming scenarios depending on the species.
Zhao, C.S., Yang, S.T., Xiang, H., Liu, C.M., Zhang, H.T., Yang, Z.L., Zhang, Y., Sun, Y., Mitrovic, S.M., Yu, Q. & Lim, R.P. 2015, 'Hydrologic and water-quality rehabilitation of environments for suitable fish habitat', Journal of Hydrology, vol. 530, pp. 799-814.
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&copy; 2015 Elsevier B.V. Aquatic ecological rehabilitation is attracting increasing public and research attention, but without knowledge of the responses of aquatic species to their habitats the success of habitat restoration is uncertain. Thus efficient study of species response to habitat, through which to prioritize the habitat factors influencing aquatic ecosystems, is highly important. However many current models have too high requirement for assemblage information and have great bias in results due to consideration of only the species' attribute of presence/absence, abundance or biomass, thus hindering the wider utility of these models. This paper, using fish as a case, presents a framework for identification of high-priority habitat factors based on the responses of aquatic species to their habitats, using presence/absence, abundance and biomass data. This framework consists of four newly developed sub-models aiming to determine weightings for the evaluation of species' contributions to their communities, to quantitatively calculate an integrated habitat suitability index for multi-species based on habitat factors, to assess the suitable probability of habitat factors and to assess the rehabilitation priority of habitat factors. The framework closely links hydrologic, physical and chemical habitat factors to fish assemblage attributes drawn from monitoring datasets on hydrology, water quality and fish assemblages at a total of 144 sites, where 5084 fish were sampled and tested. Breakpoint identification techniques based on curvature in cumulated dominance along with a newly developed weighting calculation model based on theory of mass systems were used to help identify the dominant fish, based on which the presence and abundance of multiple fish were normalized to estimate the integrated habitat suitability index along gradients of various factors, based on their variation with principal habitat factors. Then, the appropriate probability of every principal hab...
Growns, I., Chessman, B., Mitrovic, S. & Westhorpe, D.P. 2014, 'The effects of dams on longitudinal variation in river food webs', Journal of Freshwater Ecology, vol. 29, no. 1, pp. 1-14.
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We examined the effects of two dams on longitudinal variation of riverine food webs using stable isotope and gut contents analyses along four rivers in the Hunter Valley in eastern Australia. Longitudinal 15N enrichment was observed in most invertebrate taxa and food sources but significant longitudinal variation was rare for 13C, and composition of gut contents of invertebrate taxa did not vary significantly with longitudinal position. Most invertebrates and food sources were more 15N-enriched at sites immediately downstream of the dams than expected from their upstream longitudinal position, a result not mirrored by gut contents and 13C. Enrichment of 15N downstream may be attributed to altered water quality as a result of impoundment but further research is necessary to elucidate whether physico-chemical riverine processes or trophic mechanisms are responsible. Our observations regarding the influence of dams on isotope ratios are contrary to the few existing studies, suggesting the small volumes relative to annual inflows of dams in the present study limit downstream impacts by maintaining aspects of flow variability.
Jardine, T.D., Hadwen, W.L., Hamilton, S.K., Hladyz, S., Mitrovic, S., Kidd, K.A., Tsoi, W.Y., Spears, M.D., Westhorpe, D.P., Fry, V.M., Sheldon, F. & Bunn, S.E. 2014, 'Understanding and Overcoming Baseline Isotopic Variability in Running Waters', River Research and Applications.
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Natural abundances of stable isotopes in lotic food webs yield valuable information about sources of organic matter for consumers and trophic structure. However, interpretation of isotopic information can be challenging in the face of variability in organisms at the base of food webs. Unionid and dreissenid mussels, commonly used as baseline organisms in lakes, are uncommon in many river settings and can have variable diets, thus making them unsuitable as a universal baseline for many river food web studies and often forcing reliance on more common benthic insects for this purpose. Turnover rates of body carbon and nitrogen in insects are relatively rapid (1 to 50 days half-life). These rapid turnover rates in primary consumers can result in considerable temporal variability in d13C that rivals that of algae (>10%range within a site). This suggests that using primary consumers as a surrogate baseline for algae may not circumvent the problem of temporal variability and the resultant mismatch of sources with longer-lived, slow-growing secondary and tertiary consumers. There are several strategies for reducing the influence of these confounding factors when bivalves with a known diet are not present. These include sampling over large spatial scales and correlating d13C of consumers with the source of interest (e.g. benthic algae), sampling baseline organisms multiple times in the weeks preceding sampling of larger consumers (particularly in response to large changes in discharge) and using algal-detrital separation methods and multiple tracers as much as possible. Incorporating some of these recommendations and further exploring variability at the base of the food web will potentially provide greater insights into consumerresource coupling in running waters and more robust conclusions about food web structure and energy flow in these dynamic systems.
Wood, R.J., Mitrovic, S. & Kefford, B. 2014, 'Determining the relative sensitivity of benthic diatoms to atrazine using rapid toxicity testing: A novel method', The Science of the Total Environment, vol. 485-486, pp. 421-427.
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Herbicides pose a potential threat to aquatic ecosystems, especially to phototrophic organisms such as benthic diatoms. Benthic diatoms may be a valuable indicator of the toxic impacts of herbicides in aquatic systems. However, this requires information on the herbicide sensitivity of a wide range of freshwater benthic diatom taxa. Unfortunately this information is only available for a limited number of species as current methods of developing new algae toxicity tests on individual taxa are lengthy and costly. To address this issue, we developed a new rapid toxicity test method to test natural benthic communities, from which the relative herbicide sensitivity of many individual taxa can be derived. This involved the collection of natural benthic communities from rocks in situ, which were placed directly into laboratory toxicity tests. Sensitivity data for several diatom genera in a 48 hour exposure toxicity test were produced, without the need for cultures or multiple site visits. After exposure to the highest treatment of atrazine (500 &micro;g L- 1) there were significant declines of healthy cells in the most sensitive genera: Gomphonema declined by 74%, Amphora by 62%, Cymbella by 54% and Ulnaria by 34% compared to control levels. In contrast, the genera, Eunotia, Achnanthidium and Navicula, had no statistically significant decline in cell health. This method can identify the diatom taxa most at risk of herbicide toxicity within the natural benthic diatom community. The rapid toxicity testing method presented is a simple and effective method to obtain sensitivity data for multiple taxa within a natural benthic diatom community in a relatively short period of time.
Müller, S. & Mitrovic, S.M. 2014, 'Phytoplankton co-limitation by nitrogen and phosphorus in a shallow reservoir: progressing from the phosphorus limitation paradigm', Hydrobiologia, vol. 744, no. 1, pp. 255-269.
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Phosphorus (P) limitation has been regarded as the rule in freshwater systems and the basis for phytoplankton growth management. We hypothesised that P would be the limiting nutrient for phytoplankton growth in Grahamstown Dam, a shallow, mesotrophic reservoir, across different seasons and on different experimental time scales. Seven fully factorial microcosm assays with additions of nitrogen (N) and P were conducted in situ during different seasons. The influence of longer experimental duration was examined in two 18-day mesocosm assays. Additions of N and P in combination evoked significantly higher phytoplankton biomass and biovolumes of individual algal genera compared with controls and other treatments in both types of experiment. There were some significant responses to P additions in the microcosm assays in winter. Some genera first responded to combined P and N addition and then to P only addition during the mesocoms assays. Our results show that P was not the limiting nutrient across all seasons but that phytoplankton was mostly co-limited by N and P. A longer experimental time scale did not change this outcome at the biomass level. This implies that input of N as well as of P should be considered in the management of phytoplankton growth.
Davie, A.W. & Mitrovic, S.M. 2014, 'Benthic algal biomass and assemblage changes following environmental flow releases and unregulated tributary flows downstream of a major storage', Marine and Freshwater Research, vol. 65, no. 12, pp. 1059-1071.
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&copy; CSIRO 2014.A large dam reducing the magnitude of flows regulates the Severn River, Australia. Environmental flows (EFs) are designed to increase the magnitude of flow and improve ecological outcomes such as reducing filamentous algal biomass and re-setting algal succession. The effectiveness of EF releases to alter benthic algal assemblages is poorly understood. We examined benthic algal biomass and assemblage structure at two cobble-dominated riffle sites downstream of Pindari Dam, before and after two EFs. Both EFs had discharges of 11.6m3 s-1 (velocity of 0.9ms -1). Neither EF reduced benthic algal biomass, and sometimes led to increases, with density of some filamentous algae increasing (Stigeoclonium and Leptolyngbya). An unregulated flow from a tributary between the two sites increased discharge to 25.2m3 s-1 (velocity of 1.2ms-1), decreasing biomass and density of filamentous algae. The similarity in flow velocities between scouring and non-scouring events suggests that thresholds may exist and/or suspended sediments carried from unregulated tributaries may contribute to reduce algal biomass. Identifying velocities needed to reduce algal biomass are useful. Accordingly, EFs with flow velocities 1.2ms-1 may achieve this in river cobble-dominated riffle sections dominated by filamentous algae. Lower flow velocities of <0.9ms-1 may result in no change or an increase in filamentous algae.
Mitrovic, S.M., Westhorpe, D.P., Kobayashi, T., Baldwin, D.S., Ryan, D. & Hitchcock, J.N. 2014, 'Short-term changes in zooplankton density and community structure in response to different sources of dissolved organic carbon in an unconstrained lowland river: evidence for food web support', Journal of Plankton Research, vol. 36, no. 6, pp. 1488-1500.
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Hitchcock, J.N. & Mitrovic, S. 2013, 'Different resource limitation by carbon, nitrogen and phosphorus between base flow and high flow conditions for estuarine bacteria and phytoplankton', Estuarine Coastal And Shelf Science, vol. 135, no. 1, pp. 106-115.
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Freshwater inflows can deliver substantial inputs of allochthonous organic carbon to estuaries. The role that allochthonous DOC has on structuring bacterial and phytoplankton communities is still not well understood. We performed a series of 1.25 L bioassay limitation experiments on the Bega and Clyde River estuaries in NSW, Australia, examining what resources limit bacteria and phytoplankton growth. We hypothesized that during base flow conditions bacteria would be carbon limited, and after high flow conditions they would be nutrient limited. A full factorial design was used with additions of carbon (glucose), nitrogen (KNO3) and phosphorus (KH2PO4). During the experiments that took place during base flow conditions bacteria were always primarily C-limited. After high flow conditions, bacteria were P-limited on the Clyde River, and remained C-limited on the Bega River. Phytoplankton growth was limited at all times in each estuary, tending toward N-limitation on the Bega River and P-limitation on the Clyde river. During high flow conditions on the Clyde River, when bacteria and phytoplankton were both primarily P-limited, it appeared that bacteria was able to outcompete phytoplankton for nutrients. These results suggest that freshwater inflows and allochthonous DOC maybe important in structuring estuarine microbial ecosystems and individual estuaries may behave differently in terms of their limiting resources.
Zhao, C.S., Liu, C.M., Sun, Y., Yang, G., Mitrovic, S. & Wang, H. 2013, 'Heterogeneity of water quality in Huai River, China by using bio-monitoring data', Water Science & Technology: Water Supply, vol. 13, no. 6, pp. 1524-1533.
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A new approach by combining bioindicators (BiI) and biotic indices (BIs) for evaluating water quality is presented in this paper. It is then applied to the Huai River basin (HRB), China, which is well-known globally for its heavy anthropogenic influences. Results indicate that the spatial distribution of BI-indicated water quality has roughly the same pattern as that shown by BiI, but the pollution level using BI was, on average, greater than that by BiI; the northern plain area has a degraded water quality (ranging from `a-mesosaprobic to `a-polysaprobic in a wet season) while the southern mountain area and the southern part of the East Line of South-North Water Transfer Project has a better water quality (`-mesosaprobic). Water quality is worse in the dry season than in the wet season. We concluded that zoobenthos and zooplankton are more reliable indicators of water quality; biological indices are more sensitive to water quality but less reliable than BiI. These results will be of use in the ecological restoration of the Huai River and benefit water resource management in HRB in the future.
Cortez, D.P., Growns, I., Mitrovic, S. & Lim, R.P. 2012, 'Effects Of A Gradient In River Regulation On The Longitudinal Trends In Water Quality And Benthic Algal And Macroinvertebrate Assemblages In The Hunter River, Australia', Marine and Freshwater Research, vol. 63, no. 6, pp. 494-504.
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River regulation impacts lotic ecosystem processes; however, the effect of a gradient of regulation on these attributes has rarely been studied. This study examined the effects of a river regulation gradient on longitudinal trends in water quality and be
Westhorpe, D.P. & Mitrovic, S. 2012, 'Dissolved Organic Carbon Mobilisation In Relation To Variable Discharges And Environmental Flows In A Highly Regulated Lowland River', Marine and Freshwater Research, vol. 63, no. 12, pp. 1218-1230.
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The relationships between discharge and dissolved organic carbon (DOC) have been extensively studied in rainfall runoff-driven stream systems. Less is known about discharge and DOC relationships in river systems dependent on floodplain inundation. We exa
Roelke, D., Spatharis, S. & Mitrovic, S. 2012, 'A New Hydrology: Effects On Ecosystem Form And Functioning', Canadian Journal Of Fisheries And Aquatic Sciences, vol. 69, no. 8, pp. 1377-1379.
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Water cycles are changing because of human population growth and climate change. Such changes will affect fundamental system-level characteristics that in turn will greatly influence ecosystem form and functioning. Here, a collection of papers is offered
Westhorpe, D.P., Mitrovic, S. & Woodward, K.B. 2012, 'Diet Variation Of Dissolved Organic Carbon During Large Flow Events In A Lowland River', Limnologica, vol. 42, no. 3, pp. 220-226.
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Diel variation in dissolved organic carbon (DOC) within lotic systems has been reported on numerous occasions. However, to our knowledge there has been no published work on diel DOC variation within lowland rivers during high flow events. We sampled DOC
Davie, A.W., Mitrovic, S. & Lim, R.P. 2012, 'Succession and accrual of benthic algae on cobbles of an upland river following scouring', Inland Waters, vol. 2, no. 2, pp. 89-100.
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Flow releases from dams can be used to scour benthic algae, simulating the effects of natural spates and maintaining benthic algae in an early successional stage for increased grazer palatability. The timing of releases needs to consider the natural periodicity of flow events and the speed of regrowth and community succession changes. We studied benthic algal regrowth and succession using manipulative field experiments during summer and winter in the upland regulated Severn River, New South Wales, Australia. Benthic algal biomass accrual as chlorophyll a and community changes were determined after artificially scoured cobbles were returned to the river. In summer, algal biomass and diversity on scoured cobbles took 2 weeks to return to levels similar to reference cobbles and 5 weeks in winter. Chlorophyll a during summer was initially 0.24 &plusmn; 0.06 mg m-2 on scoured cobbles, but by day 16 had increased to 9.74 &plusmn; 1.97 mg m-2 and was no longer significantly different from reference cobbles. In winter, chlorophyll a was initially 0.47 &plusmn; 0.13 mg m-2 on scoured cobbles, but by day 37 had increased to 44.7 &plusmn; 10.9 mg m-2 and was no longer significantly different from reference cobbles. Peak chlorophyll a accrual during summer and winter was 1.64 and 2.63 mg m-2 d-1, respectively. Early succession in both experiments was dominated by diatoms such as Cocconeis, Synedra, and Fragilaria. A proliferation of the filamentous green alga Stigeoclonium was indicative of a late succession community. The implications for flow management based on resetting of benthic algae by scouring in riffle reaches of rivers are discussed.
Mitrovic, S., Hardwick, L. & Dorani, F. 2011, 'Use of flow management to mitigate cyanobacterial blooms in the Lower Darling River, Australia', Journal Of Plankton Research, vol. 33, no. 2, pp. 229-242.
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The growth of planktonic cyanobacteria in a weir pool on the Lower Darling River, Australia, downstream of the major regulated Menindee Lake system was examined. Blooms of the saxitoxin producing freshwater cyanobacterium Anabaena circinalis occurred for two summers out of four studied. Large cell numbers of other cyanobacteria including Aphanizomenon, Planktolyngbya and Merismopedia also occurred during the same summer periods as the Anabaena blooms. The growth events also coincided with periods of improved light climate. Flow releases from the regulated Menindee Lakes System were assessed for their ability to either suppress bloom development or to mitigate pre-existing blooms over this period.
Mitrovic, S., Hitchcock, J.N., Davie, A.W. & Ryan, D. 2010, 'Growth Responses Of Cyclotella Meneghiniana (Bacillariophyceae) To Various Temperatures', Journal Of Plankton Research, vol. 32, no. 8, pp. 1217-1221.
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The growth of Cyclotella meneghiniana was examined at temperatures between 13 and 28&deg;C at 3&deg;C intervals. Growth increased linearly with temperature to a growth maximum at 25&deg;C, with growth decreasing at 28&deg;C.
Hitchcock, J.N., Mitrovic, S., Kobayashi, T. & Westhorpe, D.P. 2010, 'Responses Of Estuarine Bacterioplankton, Phytoplankton And Zooplankton To Dissolved Organic Carbon (Doc) And Inorganic Nutrient Additions', Estuaries And Coasts, vol. 33, no. 1, pp. 78-91.
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The response of planktonic bacteria and phytoplankton to various additions of dissolved organic carbon (DOC) as glucose, with and without inorganic nutrients (nitrogen and phosphorus), was tested in the upper to mid Hunter Estuary, Australia. In situ mic
Oliver, R.L., Mitrovic, S. & Rees, C. 2010, 'Influence of salinity on light conditions and phytoplankton growth in a turbid river', River Research and Applications, vol. 26, no. 7, pp. 894-903.
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A turbid lowland river in Australia was studied to describe factors influencing the light conditions for phytoplankton growth. Vertical attenuation coefficients correlated with nepholometric turbidity enabling estimation of euphotic depths (zeu) from long term turbidity monitoring. Light conditions were assessed from the ratio of zeu to the maximum water depth (zm). Predominantly zeu/zm ratios were below 0.2, a value indicating the minimum light conditions required to support phytoplankton growth. A transitional state with zeu/zm between 0.2 and 0.35 occurred 15% of the time, while light sufficiency occurred for 30% of the time. Peaks in eukaryotic phytoplankton biomass developed when zeu/zm was at or above transitional values. Large increases in cyanobacterial numbers (Anabaena sp.) only occurred when zeu/zm exceeded 0.35. Turbidity increased quickly with elevated flows but did not decline substantially as flows reduced and light limiting conditions extended into low flow periods otherwise conducive to phytoplankton growth.
Hadwen, W.L., Fellows, C.S., Westhorpe, D.P., Rees, G.N., Mitrovic, S., Taylor, B., Baldwin, D., Silvester, E. & Croome, R. 2010, 'Longitudinal trends in river functioning: Patterns of nitrogen and carbon processing in three Australian Rivers', River Research and Applications, vol. 26, no. 9, pp. 1129-1152.
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Understanding longitudinal trends in the processing of carbon in rivers represents a much conceptualised, but infrequently tested, issue in aquatic ecology. In this study, we conducted concurrent longitudinal examinations of three very different rivers in eastern Australia to determine whether general principles in river functioning exist across broad geographic and hydrologic scales. Specifically, we examined trends in ambient basic water chemistry, nutrient concentrations, dissolved organic carbon (DOC), extracellular enzymes and food web structure and functioning and conducted bioassays to examine the degree to which DOC and nutrients limit heterotrophic bacterial respiration. These parameters revealed striking similarities across all sites. For metazoan communities, stable isotope analysis showed that algal carbon was the dominant basal resource utilised by consumers in all three rivers, suggesting that in-stream primary producers strongly underpin trophic pathways regardless of the position within a catchment or catchment condition. Analyses of extracellular enzymes revealed that microbial communities are actively utilising DOC at all sites. In fact, heterotrophic microbial respiration was strongly limited by DOC at all sites, with nutrient additions resulting in only relatively minor increases in respiration.
Westhorpe, D.P., Mitrovic, S., Ryan, D.A. & Kobayashi, T. 2010, 'Limitation Of Lowland Riverine Bacterioplankton By Dissolved Organic Carbon And Inorganic Nutrients', Hydrobiologia, vol. 652, no. 1, pp. 101-117.
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Flow regulation in lowland rivers has reduced the amount of allochthonous dissolved organic carbon (DOC) entering main channels through less frequent wetting of benches, flood runners and floodplains. The hypothesis tested was that lowland riverine bacte
Chessman, B., Westhorpe, D.P., Mitrovic, S. & Hardwick, L. 2009, 'Trophic linkages between periphyton and grazing macroinvertebrates in rivers with different levels of catchment development', Hydrobiologia, vol. 625, pp. 135-151.
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In December 1999, domoic acid (DA) a potent neurotoxin, responsible for the syndrome Amnesic Shellfish Poisoning (ASP) was detected for the first time in shellfish harvested in Ireland. Two liquid chromatography (LC) methods were applied to quantify DA in shellfish after sample clean-up using solid-phase extraction (SPE) with strong anion exchange (SAX) cartridges. Toxin detection was achieved using photodiode array ultraviolet (LC-UV) and multiple tandem mass spectrometry (LC-MSn). DA was identified in four species of bivalve shellfish collected along the west and south coastal regions of the Republic of Ireland. The amount of DA that was present in three species was within EU guideline limits for sale of shellfish (20 &micro;g DA/g); mussels (Mytilus edulis), <1.0 &micro;g DA/g; oysters (Crassostrea edulis), <5.0 &micro;g DA/g and razor clams (Ensis siliqua), <0.3 &micro;g DA/g. However, king scallops (Pecten maximus) posed a significant human health hazard with levels up to 240 &micro;g DA/g total tissues. Most scallop samples (55%) contained DA at levels greater than the regulatory limit. The DA levels in the digestive glands of some samples of scallops were among the highest that have ever been recorded (2820 &micro;g DA/g).
Mitrovic, S., Chessman, B., Davie, A.W., Avery, E.L. & Ryan, N. 2008, 'Development of blooms of Cyclotella meneghiniana and Nitzschia spp. (Bacillariophyceae) in a shallow river and estimation of effective suppression flows', Hydrobiologia, vol. 596, no. 1, pp. 173-185.
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Diatom blooms in the middle reaches of the shallow, freshwater, Hunter River, Australia, are a frequent nuisance to river users. During a 4-year study, blooms of Cyclotella meneghiniana and Nitzschia spp. coincided with water temperatures above 23&Acirc;&deg;C and flows below 400 Ml d-1 that lasted for more than 12 days. Redundancy analysis showed that water temperature was positively related, and antecedent flow was negatively related, to the abundance of both taxa. Addition experiments indicated that nutrients are seldom limiting to growth. It is suggested that a combination of faster growth rates at higher temperatures and longer retention times at low flows allows bloom populations to develop. Simulation modelling showed that flow regulation and water extraction have decreased flows in the river during summer, and consequently have probably increased the number of diatom blooms. Environmental flows have been provided to the river, but are not sufficient to prevent blooms. Discharges required for bloom suppression are described. &Acirc;&copy; 2007 Springer Science+Business Media B.V.
Ryan, N., Mitrovic, S. & Bowling, L.C. 2008, 'Temporal and spatial variability in the phytoplankton community of Myall Lakes, Australia and influences of salinity', Hydrobiologia, vol. 608, no. 1, pp. 69-86.
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The variability in the phytoplankton communities of the Myall Lakes, a series of four interconnected coastal lakes on the lower north coast of New South Wales, was studied between 1999 and 2002. There was considerable spatial variability across the lake system. Bombah Broadwater experienced blooms of Anabaena in 1999 and early 2000, but these were replaced from late 2000 onwards by Chroococcus and a variety of eukaryotic taxa, particularly flagellates and diatoms. In comparison, the phytoplankton community of Myall Lake was dominated for much of the study period by Chroococcus, Merismopedia and chlorophyte taxa. The sites located midway between these two main lakes represent an ecotone, with elements of the phytoplanktonic flora of both main lakes being present. Changes in phytoplankton community composition in Bombah Broadwater occurred fairly frequently. In contrast, the phytoplankton community in Myall Lake changed little during the course of the study and can be considered as being at long-term equilibrium. The reasons for this lie in the morphology and hydrology of the lake system, which in turn create gradients in a number of physico-chemical water quality attributes. Bombah Broadwater is influenced by episodic and stochastic freshwater inflows from the upper Myall River catchment, and in times of drought by saline marine incursions via the lower Myall River. Myall Lake however represents a cul-de-sac, with only a small hydraulic connection to the remainder of the lake system. As it has little input from its small catchment, the limnological conditions within this lake remain relatively constant for long periods of time.
Mitrovic, S., Chessman, B., Bowling, L.C. & Cooke, R.H. 2006, 'Modelling suppression of cyanobacterial blooms by flow management in a lowland river', River Research and Applications, vol. 22, no. 1, pp. 109-114.
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Growth and dominance of the cyanobacterium Anabaena circinalis in weir pools of the BarwonDarling River, Australia, are related to persistent vertical thermal stratification between October and March, when discharge is low. We determined critical velocities and discharges required to suppress bloom formation at three sites, and modelled the occurrence of sub-critical discharges in order to predict the frequency of blooms under different management scenarios. Our model suggests that the frequency of blooms was about double that expected under near-natural flows (without major impoundment or water extraction) for 19902000. Flow management, through Environmental Water Provisions that limit water extraction when river levels are low, has been in place since July 2000. Our model suggests that these provisions are unlikely to have had an effect on bloom frequency for 20002003. In the longer term, however, they could reduce bloom frequency at some sites by up to one-third
Mitrovic, S., Allis, O., Furey, A. & James, K.J. 2005, 'Bioaccumulation and harmful effects of microcystin-LR in the aquatic plants Lemna minor and Wolffia arrhiza and the filamentous alga Chladophora fracta', Ecotoxicology And Environmental Safety, vol. 61, pp. 345-352.
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Although the toxic effects of cyanotoxins on animals have been examined extensively, little research has focused on their effects on higher plants and macroalgae, and the potential for bioaccumulation in the food web through plants. Two aquatic plants, Lemna minor and Wolffia arrhiza, and one filamentous alga, Chladophora fracta, were exposed to the cyanotoxin microcystin-LR. Growth of L. minor (as weight and frond number) and root length were significantly reduced and peroxidase activity was significantly increased after 5 days of exposure to concentrations of 10 and 20 &micro;g mL-1 microcystin-LR. Growth of W. arrhiza (as frond number) was significantly reduced after 5 days of exposure to 15 &micro;g mL-1 microcystin-LR. Growth and peroxidase activity of C. fracta were not affected by microcystin-LR at concentrations up to 10 &micro;g mL-1. L. minor also accumulated microcystin-LR up to a concentration of 0.288&plusmn;0.009 ng mg-1 wet wt. plant material over the 5 days of the experiment, equivalent to an accumulation rate of 0.058 ng mg-1 day-1. C. fracta accumulated a microcystin-LR concentration of 0.042&plusmn;0.015 ng mg-1 wet wt. plant material over the 5 days of the experiment, equivalent to an accumulation rate of 0.008 ng mg-1 day-1.
Mitrovic, S., Hamilton, B., Mckenzie, L., Furey, A. & James, K.J. 2005, 'Persistence of yessotoxin (YTX) under light and dark conditions', marine environmental research, vol. 60, no. 3, pp. 397-401.
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The change in concentration of the disulfated polyether yessotoxin (YTX) produced by a culture of the marine dinoflagellate Protoceratium reticulatum was measured in laboratory experiments under light and dark conditions. Experimental cultures were inoculated and grew at a growth rate of 0.14 d-1 until stationary phase was reached, after approximately 21 days. Cultures were maintained in the stationary phase until 31 days after inoculation. Cells of P. reticulatum contained a concentration of approximately 1015 pg YTX cell-1 during stationary phase but this was considerably lower (<5 pg cell-1) during the growth phase. Low amounts of 45-hydroxy-YTX were also detected. At day 32, P. reticulatum was killed by cooling to 1 &deg;C (confirmed microscopically) and YTX concentrations were measured periodically under light and dark conditions. YTX concentrations decreased rapidly to approximately 10% of the initial concentration within the first 3 days and depleted to near zero within a week in the light treatment. In the dark environment, YTX persisted longer with approximately 10% of the initial YTX concentration still remaining after 18 days.
James, K.J., Gillman, M., Amandi, M.F., Lopez-Rievra, A., Puente, P.F., Lehane, M., Mitrovic, S. & Furey, A. 2005, 'Amnesic shellfish poisoning toxins in bivalve molluscs in Ireland', Toxicon, vol. 46, no. 8, pp. 852-858.
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In December 1999, domoic acid (DA) a potent neurotoxin, responsible for the syndrome Amnesic Shellfish Poisoning (ASP) was detected for the first time in shellfish harvested in Ireland. Two liquid chromatography (LC) methods were applied to quantify DA in shellfish after sample clean-up using solid-phase extraction (SPE) with strong anion exchange (SAX) cartridges. Toxin detection was achieved using photodiode array ultraviolet (LC-UV) and multiple tandem mass spectrometry (LC-MSn). DA was identified in four species of bivalve shellfish collected along the west and south coastal regions of the Republic of Ireland. The amount of DA that was present in three species was within EU guideline limits for sale of shellfish (20 &micro;g DA/g); mussels (Mytilus edulis), <1.0 &micro;g DA/g; oysters (Crassostrea edulis), <5.0 &micro;g DA/g and razor clams (Ensis siliqua), <0.3 &micro;g DA/g. However, king scallops (Pecten maximus) posed a significant human health hazard with levels up to 240 &micro;g DA/g total tissues. Most scallop samples (55%) contained DA at levels greater than the regulatory limit. The DA levels in the digestive glands of some samples of scallops were among the highest that have ever been recorded (2820 &micro;g DA/g).
Mitrovic, S., Amandi, M.F., Mckenzie, L., Furey, A. & James, K.J. 2004, 'Effects of selenium, iron and cobalt addition to growth and yessotoxin production of the toxic marine dinoflagellate Protoceratium reticulatum in culture', Journal of Experimental Marine Biology and Ecology, vol. 313, no. 2, pp. 337-351.
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he marine dinoflagellate Protoceratium reticulatum has been recently identified as a source for the disulfated polyether toxin, yessotoxin (YTX), and may pose a risk to human health, aquaculture development and coastal environments. The requirements of P. reticulatum for selenium, iron and cobalt were assessed in culture. P. reticulatum was grown in nutrient enriched seawater (1/10 GP medium) without selenium or with 0.003 and 0.0003 &micro;M selenium added; without iron or with 0.076 and 0.0076 &micro;M iron added; and without cobalt or with 0.008 &micro;M cobalt added. Test flasks were monitored for growth rate, cell yield and YTX production. P. reticulatum was found to exhibit a strong requirement for both selenium and iron. Growth rate and cell yield in treatments without added selenium were significantly (P<0.05) reduced to 60.2% (&micro;=0.15 day-1) and 20.2% (4942 cell ml-1), respectively, of those with selenium added (&micro;=0.23 day-1 and 24, 387 cell ml-1). YTX production was significantly increased by addition of selenium in two of three transfers tested. Cells of P. reticulatum subjected to medium without selenium added showed morphological changes observable at the light microscope level which included enlarged cell size. The diameter of cells in medium without selenium added were significantly (P<0.05) enlarged to 36.7&plusmn;0.90 &micro;m compared to cells in the medium with selenium added, 27.5&plusmn;1.25 &micro;m. Growth rate and cell yield in treatments without added iron were also significantly reduced to 70.1% (&micro;=0.16 day-1) and 34.2% (8003 cells ml-1), respectively, of those with iron added (&micro;=0.23 day-1 and 23,416 cells ml-1). No significant effect on YTX production was measured. In contrast to selenium and iron, no limitation of growth or cell yield or differences in YTX production were observed for flasks without cobalt as compared to those with cobalt added. The possibility that harmful algal events of P. reticulatum may be influenced by selenium or iron in neritic waters is discussed.
Mitrovic, S., Pflugmacher, S., James, K.J. & Furey, A. 2004, 'Anatoxin-a elicits an increase in peroxidase and glutathione S-transferase activity in aquatic plants', Aquatic Toxicology, vol. 68, no. 2, pp. 185-192.
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Although the toxic effects of cyanotoxins on animals have been examined extensively, little research has focused on their effects on macrophytes and macroalgae. To date only microcystins have been found to be detrimental to aquatic plants. Peroxidase activity of the free floating aquatic plant Lemna minor and the filamentous macroalga Chladophora fracta was measured after exposure to several concentrations of the cyanotoxin, anatoxin-a. Peroxidase activity (POD) was significantly (P<0.05) increased after 4 days of exposure to an anatoxin-a concentration of 25 &micro;g mL-1 for both L. minor and C. fracta. Peroxidase activity was not significantly increased at test concentrations of 15 &micro;g mL-1 or lower. In another experiment, the effects of various concentrations of anatoxin-a on the detoxication enzyme, glutathione S-transferase (GST) in L. minor were investigated. GST activity was significantly elevated at anatoxin-a concentrations of 5 and 20 &micro;g mL-1. Photosynthetic oxygen production by L. minor was also found to be reduced at these concentrations. This is the first report to our knowledge of the cyanotoxin anatoxin-a being harmful to aquatic plants.
Mitrovic, S.M., Pflugmacher, S., James, K.J. & Furey, A. 2004, 'Anatoxin-a elicits an increase in peroxidase and glutathione S-transferase activity in aquatic plants', AQUATIC TOXICOLOGY, vol. 68, no. 2, pp. 185-192.
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Mitrovic, S., Oliver, R.L., Rees, C., Bowling, L.C. & Buckney, R.T. 2003, 'Critical flow velocities for the growth and dominance of Anabaena circinalis in some turbid freshwater rivers', Freshwater Biology, vol. 48, pp. 164-174.
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Mitrovic, S., Howden, C.G., Bowling, L.C. & Buckney, R.T. 2003, 'Unusual allometry between in situ growth of freshwater phytoplankton under static and fluctuating light environments: possible implications for dominance', Journal Of Plankton Research, vol. 25, no. 5, pp. 517-526.
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Mitrovic, S., Bowling, L.C. & Buckney, R.T. 2001, 'Responses of phytoplankton to in-situ nutrient enrichment: Potential Influences on Species Dominance in a River', International Review of Hydrobiology, vol. 86, no. 3, pp. 283-296.
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The Hawkesbury River at Sackville, New South Wales, Australia is fresh and vigorously mixed by tidal movement. The location has frequent blooms of Microcystis aeruginosa, which have been recorded occurring throughout the year, including winter temperatures as low as 13 &deg;C. Nutrient enrichment tests were performed in-situ on the natural phytoplankton population in 1997 and 1998 while Microcystis aeruginosa dominated (covering both summer and winter periods). These experiments compared population changes under the ambient nutrient regime with those after additions of ortho-phosphate, nitrate, ammonia and various combinations of these nutrients. Under ambient conditions, the Microcystis population was able to grow significantly (P < 0.05) while most non-cyanobacterial phytoplankton did not. Nutrient additions induced a variety of nutrient limitation responses that often varied between genera of major groups i.e. in the Chlorophyceae (Actinastrum sp. responded to phosphorus while Psephonema sp. responded to nitrogen). The possibility that shifts in population dominance from Chlorophyceae to the Cyanobacteria (M. aeruginosa) at Sackville are in response to competition for limiting nutrients is discussed
Mitrovic, S., Bowling, L.C. & Buckney, R.T. 2001, 'Quantifying potential benefits to Microcystic aeruginosa through disentrainment by buoyancy within an embayment of a freshwater river', Journal of Freshwater Ecology, vol. 16, no. 2, pp. 151-157.
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Vertical profiles of Microcystis aeruginosa and other phytoplankton were measured on several occasions within the main channel and an embayment of a freshwater tidal river. The cyanobacteria M. aeruginosa and Anabaena circinalis were able to migrate to surface waters within the embayment but not within the main channel. Using a quantitative estimate of primary productivity (over a 24 hour period), the potential benefits through disentrainment by buoyancy were determined for M. aeruginosa within the embayment and compared to the main channel. The population within the embayment had a daily integral of photosynthesis of 603.13 mmol of O(2)m(-2), nine times greater than the evenly distributed main channel population with a daily integral of 62.08 mmol of O(2)m(-2). It is likely that embayments along the tidally mixed reaches of the Hawkesbury River may be areas where M. aeruginosa can disentrain through buoyancy and enhance primary productivity rates.
Mitrovic, S., Bowling, L.C. & Buckney, R.T. 2001, 'Vertical Disentrainment of Anabaena circinalis in the Turbid Freshwater Darling River, Australia: Qunatifying Potential Benefits from Buoyancy', Journal of Plankton Research, vol. 23, pp. 47-55.
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Mitrovic, S.M., Bowling, L.C. & Buckney, R.T. 2001, 'Responses of phytoplankton to in-situ nutrient enrichment; Potential influences on species dominance in a river', INTERNATIONAL REVIEW OF HYDROBIOLOGY, vol. 86, no. 3, pp. 285-298.
M. Mitrovic, S., Bowling, L.C. & Buckney, R.T. 2001, 'Responses of Phytoplankton toin-situ Nutrient Enrichment; Potential Influences on Species Dominance in a River', International Review of Hydrobiology, vol. 86, no. 3, pp. 285-298.
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M. Mitrovic, S., Bowling, L.C. & Buckney, R.T. 2001, 'Responses of Phytoplankton to in-situ Nutrient Enrichment; Potential Influences on Species Dominance in a River', International Review of Hydrobiology, vol. 86, no. 3, pp. 285-298.
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