Authors: Archana Venkatachari, Darcy Perin, Margaret Gordon, Margaret Gaspar, Grace Hurley, Annie Bourbonnais, Ioannis Rekleitis, Dwane Porter, Geoff Scott, Ronald Willis and Kara Clyburn, Dan Tufford, Stacie Gantz, Robin Kloot, Thomas Hogan
Abstract: Harmful Cyanobacterial Blooms (HCBs) are increasingly common in South Carolina lakes and pose a threat to the health of humans and the ecosystem. Lake Wateree, a hydroelectric reservoir, is subjected to extensive perennial benthic and seasonal surface mats of the filamentous cyanobacteria Microseira (Lyngbya) wollei and Phormidium spp. The broader goal of this project is to better understand the physical and chemical factors leading to the proliferation of HCBs using a combination of discrete and high spatial resolution sampling from autonomous surface vehicles equipped with water quality sensors. In this presentation, we discuss water-column nutrient concentrations, collected every two months at four stations in Lake Wateree from 2015 to 2021, in collaboration with a citizen-science project (Lake Wateree Association). The data shows that water-column ortho-phosphate is generally depleted, suggesting an organic and/or benthic source of phosphorus. We observe seasonal variability in dissolved nitrogen concentrations, with Inorganic Nitrogen (IN) becoming gradually depleted during summer as the bloom progresses. Organic Nitrogen (ON) comprises the major portion of water-column nitrogen near the end of the bloom, suggesting an important role for ON as the main nitrogen source for phytoplankton and microbial communities. Recycling of algal biomass during the bloom may also be an important mechanism regulating HCBs during this period.