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Cyanobacterial blooms in eutrophic freshwater is a global threat to the functioning of ecosystems, human health and the economy. Parties responsible for the ecosystems and human health increasingly demand reliable predictions of cyanobacterial development to support necessary decisions. Long-term data series help with identifying environmental drivers of cyanobacterial developments in the context of climatic and anthropogenic pressure. Here, we analyzed 13 years of eutrophication and climatic data of a shallow temperate reservoir showing a high interannual variability of cyanobacterial development and composition, which is a less occurring and/or less described phenomenon compared to recurrant monospecific blooms. While between 2007–2012 Planktothrix agardhii dominated the cyanobacterial community, it shifted towards Microcystis sp. and then Dolichospermum sp. afterwards (2013–2019). The shift to Microcystis sp. dominance was mainly influenced by generally calmer and warmer conditions. The later shift to Dolichospermum sp. was driven by droughts influencing, amongst others, the N-load, as P remained unchanged over the time period. Both, climatic pressure and N-limitation contributed to the high variability of cyanobacterial blooms and may lead to a new equilibrium. The further reduction of P-load in parallel to the decreasing N-load is important to suppress cyanobacterial blooms and ameliorate ecosystem health.
Morgane Le Moal; Alexandrine Pannard; Luc Brient; Benjamin Richard; Marion Chorin; Emilien Mineaud; Claudia Wiegand. Is the Cyanobacterial Bloom Composition Shifting Due to Climate Forcing or Nutrient Changes? Example of a Shallow Eutrophic Reservoir. Toxins 2021, 13, 351 .
AMA StyleMorgane Le Moal, Alexandrine Pannard, Luc Brient, Benjamin Richard, Marion Chorin, Emilien Mineaud, Claudia Wiegand. Is the Cyanobacterial Bloom Composition Shifting Due to Climate Forcing or Nutrient Changes? Example of a Shallow Eutrophic Reservoir. Toxins. 2021; 13 (5):351.
Chicago/Turabian StyleMorgane Le Moal; Alexandrine Pannard; Luc Brient; Benjamin Richard; Marion Chorin; Emilien Mineaud; Claudia Wiegand. 2021. "Is the Cyanobacterial Bloom Composition Shifting Due to Climate Forcing or Nutrient Changes? Example of a Shallow Eutrophic Reservoir." Toxins 13, no. 5: 351.
Primary consumers in freshwater ecosystems, such as the zooplankton organism Daphnia magna, are highly affected by cyanobacteria, both as they may use it as a food source but also by cyanobacterial metabolites present in the water. Here, we investigate the impacts of cyanobacterial metabolites focussing on the environmental realistic scenario of the naturally released mixture without crushing cyanobacterial cells or their uptake as food. Therefore, D. magna were exposed to two concentrations of cell free cyanobacterial spent medium from Microcystis aeruginosa PCC 7806 to represent higher and lower ecologically-relevant concentrations of cyanobacterial metabolites. Including microcystin-LR, 11 metabolites have been detected of which 5 were quantified. Hypothesising concentration and time dependent negative impact, survival, gene expression marking digestion and metabolism, oxidative stress response, cell cycle and molting as well as activities of detoxification and antioxidant enzymes were followed for 7 days. D. magna suffered from oxidative stress as both catalase and glutathione S-transferase enzyme activities significantly decreased, suggesting enzyme exhaustibility after 3 and 7 days. Moreover, gene-expressions of the 4 stress markers (glutathione S-transferase, glutathione peroxidase, catalase and thioredoxin) were merely downregulated after 7 days of exposure. Energy allocation (expression of glyceraldehyde-3-phosphate dehydrogenase) was increased after 3 days but decreased as well after 7 days exposure. Cell cycle was impacted time dependently but differently by the two concentrations, along with an increasing downregulation of myosin heavy chain responsible for cell arrangement and muscular movements. Deregulation of nuclear hormone receptor genes indicate that D. magna hormonal steering including molting seemed impaired despite no detection of microviridin J in the extracts. As a consequence of all those responses and presumably of more than investigated molecular and physiological changes, D. magna survival was impaired over time, in a concentration dependent manner. Our results confirm that besides microcystin-LR, other secondary metabolites contribute to negative impact on D. magna survival and stress response.
Gorenka Bojadzija Savic; Hervé Colinet; Myriam Bormans; Christine Edwards; Linda A. Lawton; Enora Briand; Claudia Wiegand. Cell free Microcystis aeruginosa spent medium affects Daphnia magna survival and stress response. Toxicon 2021, 195, 37 -47.
AMA StyleGorenka Bojadzija Savic, Hervé Colinet, Myriam Bormans, Christine Edwards, Linda A. Lawton, Enora Briand, Claudia Wiegand. Cell free Microcystis aeruginosa spent medium affects Daphnia magna survival and stress response. Toxicon. 2021; 195 ():37-47.
Chicago/Turabian StyleGorenka Bojadzija Savic; Hervé Colinet; Myriam Bormans; Christine Edwards; Linda A. Lawton; Enora Briand; Claudia Wiegand. 2021. "Cell free Microcystis aeruginosa spent medium affects Daphnia magna survival and stress response." Toxicon 195, no. : 37-47.
While the intracellular function of many toxic and bioactive cyanobacterial metabolites is not yet known, microcystins have been suggested to have a protective role in the cyanobacterial metabolism, giving advantage to toxic over nontoxic strains under stress conditions. The zooplankton grazer Daphnia reduce cyanobacterial dominance until a certain density, which may be supported by Daphnia exudates, affecting the cyanobacterial physiological state and metabolites' production. Therefore, we hypothesized that D. magna spent medium will impact the production of cyanobacterial bioactive metabolites and affect cyanobacterial photosynthetic activity in the nontoxic, but not the toxic strain. Microcystin (MC-LR and des-MC-LR) producing M. aeruginosa PCC7806 and its non-microcystin producing mutant were exposed to spent media of different D. magna densities and culture durations. D. magna spent medium of the highest density (200/L) cultivated for the shortest time (24 h) provoked the strongest effect. D.magna spent medium negatively impacted the photosynthetic activity of M. aeruginosa PCC7806, as well as the dynamics of intracellular and extracellular cyanobacterial metabolites, while its mutant was unaffected. In the presence of Daphnia medium, microcystin does not appear to have a protective role for the strain. On the contrary, extracellular cyanopeptolin A increased in M. aeruginosa PCC7806 although the potential anti-grazing role of this compound would require further studies.
Gorenka Bojadzija Savic; Christine Edwards; Enora Briand; Linda Lawton; Claudia Wiegand; Myriam Bormans. Daphnia magna Exudates Impact Physiological and Metabolic Changes in Microcystis aeruginosa. Toxins 2019, 11, 421 .
AMA StyleGorenka Bojadzija Savic, Christine Edwards, Enora Briand, Linda Lawton, Claudia Wiegand, Myriam Bormans. Daphnia magna Exudates Impact Physiological and Metabolic Changes in Microcystis aeruginosa. Toxins. 2019; 11 (7):421.
Chicago/Turabian StyleGorenka Bojadzija Savic; Christine Edwards; Enora Briand; Linda Lawton; Claudia Wiegand; Myriam Bormans. 2019. "Daphnia magna Exudates Impact Physiological and Metabolic Changes in Microcystis aeruginosa." Toxins 11, no. 7: 421.