D'Angelo Scope 8-104B Water Resources Research Institute Annual Base Program 2021-2026

Public health advisories have been issued at numerous KY lakes and reservoirs due to elevated microcystin concentrations. Microcystins are a class of >100 closely-related toxins produced by naturally-occurring cyanobacteria (commonly known as “blue-green algae”) which can lead to liver necrosis and death in people, pets, and wildlife that ingest contaminated water. To better protect human and animal health, improved understanding of the physicochemical and ecological factors that control cyanobacterial growth and microcystin production are greatly needed. Cyanobacteria are photosynthetic organisms whose overall growth is governed by light, temperature, and nutrient concentrations, as well as by complex positive and negative interactions with other aquatic organisms. Factors that induce cyanobacteria to produce microcystins, however, are not well established which makes it very difficult to minimize or predict hazard risks. Recent research performed under greenhouse conditions by undergraduate students mentored by the PI showed that increasing phosphate concentrations in hypereutrophic lake water more than doubled both N2 fixation rates and total nitrogen concentrations, and quadrupled microcystin production. These results indicate that phosphate stimulated N2-fixation by certain diazotrophs and the freshly-fixed nitrogen was released and utilized for microcystin production, possibly by other cyanobacterial groups. If these results hold true under in situ conditions, then management practices that reduce phosphorus inputs to aquatic ecosystems could be an effective means for reducing HAB hazard risks. Clearly, a better understanding of ecological and other factors that regulate microcystin production would be helpful in developing effective nutrient management strategies for controlling microcystin production. The main objective of this research and undergraduate student training project is to more clearly elucidate the ecological linkages between nutrient amendments, nitrogen-fixation, and microcystin gene expression/production by phytoplankton communities in a hypereutrophic lake. This goal will be accomplished by monitoring changes in water quality parameters (temperature, pH, dissolved oxygen, chlorophyll a, total nitrogen, total phosphorus, and microcystin concentrations), N2-fixation rates, and expression of microcystin genes and N cycling genes by metabolically-active phytoplankton in in situ nutrient-amended microcosms installed in a hypereutrophic lake during harmful algal bloom season. Results from the project will greatly illuminate effects of nutrient amendments on phytoplankton community activities/composition and microcystin gene expression/production which will ultimately lead to improved management decisions for reducing HAB hazard risks. This project provides opportunities for two undergraduate students to conduct advanced limnological research, collaborate with representatives of state and federal agencies (e.g. KY DOW and USACE), compete for other competitive research grants, and present research results at numerous venues hosted by KWRRI and University of Kentucky Office of Undergraduate Research.