Recurring cyanobacterial harmful algal blooms (cHABs) dominated by Microcystis in the western basin of Lake Erie, and increasingly in water bodies worldwide, produce the toxin microcystin. This presents a significant and growing global threat to ecosystems, drinking water security, and human health. This project aims to improve understanding of the environmental and physiological factors that regulate microcystin production to ultimately improve cHAB toxin forecasts, with broad implications for affected regions on a global scale.
Why We Care
Cyanobacterial blooms in Lake Erie produce microcystin, a potent cyanotoxin that poses a significant threat to ecosystem function, drinking water security, and human health. The 2014 Toledo, Ohio, water crisis, caused by microcystin contamination, highlights the urgent need for better prediction of toxin production.
Current Lake Erie cHAB forecast models equate biomass with toxicity. This is inadequate because microcystin production varies within a bloom, and is influenced by environmental and physiological stimuli. A major knowledge gap exists regarding how different Microcystis strains respond to nitrogen availability. Preliminary data indicate that some strains increase toxin with nitrogen while others decrease it — an uncharacterized “toxin phenotype” that differs among strains. Understanding these phenotypes is crucial for accurate forecasting of cHAB toxicity.
What We Are Doing
This competitive financial assistance award supports work to characterize Microcystis phenotypes and determine how different phenotypes respond to nitrogen availability to influence toxicity during a bloom. Results will be used to incorporate toxin phenotype parameters into an existing forecast model to predict microcystin production based on physiological and environmental parameters.
This project aims to:
- Screen Microcystis strains to determine toxin phenotypes: Using continuous cultures, researchers will screen Microcystis aeruginosa strains to determine their toxin phenotypes in response to varying nitrate concentrations.
- Test effects of nitrogen from different sources: The effects of nitrogen source (urea and ammonium) on strains with different toxin phenotypes will be evaluated to determine how nitrogen source influences toxin production within and among strains.
- Characterize the molecular mechanism: ‘Omics will be used to identify the molecular mechanisms that govern the differing responses to nitrogen, including the effect of the nitrogen regulator NtcA on mcy genes responsible for microcystin biosynthesis.
- Advance prediction of Lake Erie cHAB toxicity: Results will be incorporated into an existing mechanistic model of Microcystis growth and microcystin production and validated by mesocosm studies of natural Lake Erie bloom populations.
Microcystis aeruginosa in culture flasks. Credit: R. Martin.
Benefits of Our Work
The central objective of this project is to close the knowledge gap related to opposing phenotypes of Microcystis, thus improving quantitative understanding of toxin biosynthesis and the environmental cues that regulate toxin production. Research products will enhance harmful algal bloom forecasting capabilities in Lake Erie to protect human health and enhance drinking water security.
This project advances current cHAB forecasting capabilities toward predicting toxic impacts to serve the needs expressed by Lake Erie resource managers, and has broader application to freshwater lakes and estuaries everywhere Microcystis blooms occur.
Robbie Martin and Steven Wilhelm of the University of Tennessee co-lead this project with partners at Ohio State University and the State University of New York College of Environmental Science and Forestry (SUNY-ESF).
The project is funded through the NCCOS Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) Program and authorized under the Harmful Algal Bloom and Hypoxia Research and Control Act (33 U.S.C. §§ 4001 et seq.), which authorizes NOAA to detect and monitor harmful algae.