The Great Lakes experience recurrent toxin-producing cyanobacterial harmful algal blooms (cHABs). While cHAB events have been well-studied in recent years, little attention has been given to acidification in the Great Lakes. Using a combination of laboratory and field studies, ‘Omics techniques, and sedimentary analysis, this project aims to advance a holistic understanding of the combined impacts of acidification, temperature, alkalinity, and nutrients on toxic cHAB formation and progression to understand past trends and better predict and respond to future events. Project results will aid the development and validation of biogeochemical models which are lacking essential carbon data in the Great Lakes, models of potential phytoplankton assemblage shifts occurring with acidification, and cHAB toxin forecasts.
Why We Care
Lake Erie and Lake Huron experience recurrent cyanobacterial harmful algal blooms (cHABs) and these events have occurred recently in Lake Superior. While cHAB events have been well-studied in recent years, little attention has been given to acidification in the Great Lakes. Acidification has not been adequately monitored and there is a lack of understanding of the potential impacts of acidification on the Great Lakes ecosystem. Shifts in alkalinity and nutrient availability resulting from changes in precipitation and stratification may have synergistic impacts with co-occurring acidification and warming that promote cHABs within the Great Lakes. This project will advance a holistic understanding of the impact of acidification, temperature, alkalinity, and nutrients on toxic cHAB formation and progression to better predict and respond to future events.
What We Are Doing
The project team will leverage existing environmental data sets with new laboratory and field studies to determine the individual and combined effects of acidification, total alkalinity, temperature, and nitrogen concentrations on cHAB growth and toxin production in three Great Lakes (Erie, Huron, and Superior).
This project aims to
- Determine the combined effects of acidification, temperature, total alkalinity, and nitrogen type on cyanobacteria growth and toxin production, and their influence on phytoplankton community structure;
- Determine how the abundance and expression of key genetic markers vary with inorganic carbon, pH, and nutrient availability at different Great Lakes sampling sites; and
- Analyze sedimentary DNA records to determine changes in the phytoplankton community with historical trends of carbon and temperature in the Great Lakes.
Through a combination of laboratory and field-based experiments, the project team will study two toxin-producing cyanobacteria that often dominate cHABs in the Great Lakes, Microcystis aeruginosa and Dolichospermum lemmermannii. Studies will incorporate ‘Omics techniques to elucidate the influence of inorganic carbon, pH, and nutrient availability on bloom community composition, metabolism, and expression of toxin production genes in laboratory cultures and field samples and across natural environmental gradients in the Great Lakes. The team will analyze DNA and toxin production genes preserved in sediment from the western basin of Lake Erie, where cHABs have the highest current impacts and the longest known history, to extend the history of cHAB activity and assess changes over time. These data will be coupled with direct measurements of cyanobacterial toxins in sediment. This unparalleled historical record (~ 150 years) of cHABs in the Great Lakes will allow investigators to infer how past trends in acidification impacted phytoplankton communities and will inform future cHAB predictions.
Impact/Benefits of our Work
Outcomes from this project will further our understanding of factors that influence phytoplankton assemblage, cyanobacteria strain succession, and the role of carbon, temperature, alkalinity and nutrients in promoting toxic cHABs within Great Lakes ecosystems. Current cHAB forecasts do not take into account cyanobacteria type or strain differences, limiting their ability to forecast when and where cHABs produce toxins. Connecting environmental data (acidification, temperature, alkalinity, and nitrogen) to growth, cyanotoxin, and ‘Omics data will advance understanding of the factors affecting bloom succession and toxin production and enhance prediction of cHAB events.
The project results will aid the development and validation of biogeochemical models which are lacking essential carbon data in the Great Lakes, models of potential phytoplankton assemblage shifts occurring with acidification, and cHAB toxin forecasts. Project data will directly inform the Great Lakes Water Quality Agreement’s management goals and will be coupled to current forecasting efforts at NOAA’s Great Lakes Environmental Research Laboratory (GLERL) and National Centers for Coastal Ocean Science (NCCOS). Project results will improve the capability of current NOAA cHAB decision support tools – the HAB Forecast Bulletin for Lake Erie and the Lake Erie HAB Forecast – to forecast toxins during cHAB events.
Dr. Reagan Errera of NOAA GLERL and Dr. Gregory Dick of the University of Michigan and NOAA’s Cooperative Institute for Great Lakes Research (CIGLR) co-lead this project. Co-investigators are Dr. Rachel Eveleth of Oberlin College, Dr. Jenan Kharbush of the University of Michigan, Dr. Cody Sheik of the University of Minnesota-Duluth, Dr. Trisha Spanbauer of the University of Toledo, and Dr. Kevin Yeager of the University of Kentucky..
The project is funded through the NCCOS Competitive Research Program, in partnership with NOAA’s Ocean Acidification Program.