EAGER: Development of the cyanotoxins, cylindrospermopsin and microcystin, as paleolimnological tools

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The quality of water in lakes changes with increasing temperature and nutrient enrichment that leads to algal blooms. Increases in algal blooms typically include cyanobacteria, which are capable of producing toxins called cyanotoxins. These cyanotoxins are harmful to human health and to other animals that live in or drink water from the lakes. There is little, historical data on algal blooms and cyanotoxins, which makes it difficult to understand how long they have been occurring and what makes them happen. This project will advance our understanding of algal blooms and cyanotoxin occurrence by focusing on the historical record of cyanotoxins that are preserved in the sediments of lakes. There are significant challenges in relating the cyanotoxin in lake sediments to their historic production in the water column of lakes. This EAGER project will develop innovative methods to extract and measure cyanotoxins in lake sediment, and conduct experiments to quantify how the toxins degrade under various environmental conditions. Researchers will then make critical determinations of historic production of these toxins for Lake Harris in Florida. Results from this project will be broadly useful in developing standard methods for the study of cyanotoxins in all lakes and reservoirs, and will provide lake and municipal water managers a new tool to acquire cyanotoxin data on a longer time scale. This project will also provide research training for graduate, undergraduate and high school students, including members of underrepresented groups. While these paleolimnological investigations are providing much needed records of historic cyanotoxin production, it is unknown if changes in paleo-cyanotoxin stratigraphies result from alterations in toxin production, degradation or deposition. As a result, sediment studies incorporating cyanotoxins as a proxy are at risk to incorrectly infer historic toxin production. This research will establish cyanotoxin water-sediment connections, develop innovative analytical protocols, and cutting-edge degradation indices for determining cyanotoxin sediment studies on cylindrospermopsin and microcystin. In addition, results from these experiments will used to verify cyanotoxin deposition with known periods of historic eutrophication and limnological change throughout the Holocene. The objectives of the study are: 1) develop sediment-water column connections for cyanotoxins by matching surface sediment cyanotoxin concentrations with known water column cyanotoxin values and improving extraction methods, 2) determine degradation coefficients for CYN and MC in a variety of sediment types under a range of environmental variables (temperature, oxygen, organic matter content) experienced in lake sediment environments, and 3) identify stratigraphic changes of cyanotoxins and cyanobacteria pigments from sediment cores.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.