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Dr Simon Mitrovic

Biography

I have  dual roles as a Senior Research Scientist with the NSW Office of Water and as a Senior Lecturer in The School of the Environment. As an applied scientist focusing on freshwater ecology, environmental flows and plant ecotoxicology part of my role with the Office of Water is to ensure that students are exposed to industry related issues and undertake research relevant to industry needs.

Professional

Scientific Committees and editorial boards

  • Core member of the Centre for Environmental Sustainability, UTS
  • 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 the Environment
Core Member, Centre for Environmental Sustainability
PhD (UTS)
 
Phone
+61 2 9514 8297
Room
CB04.05.48B

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.
  2. James Hitchcock (2005-06) Effects of environmental flow delivery of carbon on productivity in the Hunter estuary, UTS.
  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).
  5. Richard Carney (2013) Bacterial community changes in response to flow events in the Hunter Estuary UTS (With Dr Justin Seymour).
  6. Steven Leahey (2013) Antimony concentrations in waters and sediments of the Bellinger Estuary (With Dr Simon Apte - CSIRO).

Current Honours students

  1. Carla Thomas (2013) Effects of cyanotoxin exposure on higher plants and the synergistic impacts of other stressors

Graduated Masters students

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

Current Masters Students

  1. Rachel Gray - Effectiveness of thermal pollution mitigation using a novel thermal curtain.

Completed / submitted PhD Students

  1. Alec Davie - The influence of environmental flows on periphyton communities in the Severn River, NSW, UTS. * Submitted.
  2. Stefanie Mueller - Limitation of phytoplankton and sediment release of nutrients in a shallow reservoir, UTS.

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*
  2. James Hitchcock - The effect of environmental flows and nutrient and carbon inflows on the planktonic foodweb in the Bega River Estuary, UTS.* 
  3. Rebecca Herron – Algae as bioindicators of herbicide pollution in the Great Barrier Reef catchments.UTS *
  4. Maxine Mowe - Cyanobacterial toxins in Singapore’s Reservoirs; identifying progenitor species, toxin production rates and responses to environmental variables, National University of Singapore. 
  5. Ben Woodward – Mobilisation of carbon on soils in the Gwydir River – Griffith University.

* indicates primary supervisor

Journal articles

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.
Wood, R.J., Mitrovic, S.M. & Kefford, B.J. 2014, 'Determining the relative sensitivity of benthic diatoms to atrazine using rapid toxicity testing: A novel method', SCIENCE OF THE TOTAL ENVIRONMENT, vol. 485, pp. 421-427.
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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.O., Mitrovic, S.M. & 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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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.M. & 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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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. 2012, 'Understanding and Overcoming Baseline Isotopic Variability in Running Waters', River Research and Applications, vol. Online, pp. 1-11.
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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.
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.M., Hitchcock, J.N., Davie, A.W. & Ryan, D.A. 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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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 g DA/g); mussels (Mytilus edulis), <1.0 g DA/g; oysters (Crassostrea edulis), <5.0 g DA/g and razor clams (Ensis siliqua), <0.3 g DA/g. However, king scallops (Pecten maximus) posed a significant human health hazard with levels up to 240 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 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 23C 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. 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 g mL-1 microcystin-LR. Growth of W. arrhiza (as frond number) was significantly reduced after 5 days of exposure to 15 g mL-1 microcystin-LR. Growth and peroxidase activity of C. fracta were not affected by microcystin-LR at concentrations up to 10 g mL-1. L. minor also accumulated microcystin-LR up to a concentration of 0.2880.009 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 0.0420.015 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 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., Lpez-Rivera, 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-MS(n)). 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 microg DA/g); mussels (Mytilus edulis), <1.0 microg DA/g; oysters (Crassostrea edulis), <5.0 microg DA/g and razor clams (Ensis siliqua), <0.3 microg DA/g. However, king scallops (Pecten maximus) posed a significant human health hazard with levels up to 240 microg 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 (2,820 microg 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 M selenium added; without iron or with 0.076 and 0.0076 M iron added; and without cobalt or with 0.008 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% (=0.15 day-1) and 20.2% (4942 cell ml-1), respectively, of those with selenium added (=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 36.70.90 m compared to cells in the medium with selenium added, 27.51.25 m. Growth rate and cell yield in treatments without added iron were also significantly reduced to 70.1% (=0.16 day-1) and 34.2% (8003 cells ml-1), respectively, of those with iron added (=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 g mL-1 for both L. minor and C. fracta. Peroxidase activity was not significantly increased at test concentrations of 15 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 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., 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.
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 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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