Poster Details
SEASONAL NUTRIENT LIMITATION OF PHYTOPLANKTON IN A HYPER-EUTROPHIC RESERVOIR: THE ROLE OF PHOSPHORUS AND NITROGEN FORM
Nitrogen (N) and phosphorus (P) inputs impact the structure and function of algal communities, and excess supply results in harmful algal blooms (HABs). N and P loading is influenced by watershed landuse activities and seasonal discharge patterns. However, the interaction between seasonality in nutrient supply and algal nutrient limitation remains poorly understood. We examined these processes in Acton Lake, a hyper-eutrophic reservoir in Ohio, that experiences high nutrient inputs from watershed agriculture. Dissolved inorganic N inputs to Acton Lake are declining, which could promote N-limited cyanobacterial blooms. We focused on how phytoplankton groups are limited by N or P, and by different N forms (ammonium vs. nitrate). We quantified limitation with bioassay experiments weekly for 21 weeks in 2018. Phytoplankton were P-limited early in the growing season, transitioned to N-limitation in early summer, and returned to P-limitation following fall turnover. During the N-limitation period, green algae and cyanobacteria were strongly limited by ammonium, whereas diatoms responded strongly to nitrate addition. Cyanobacteria heterocyst development largely followed the onset of N-limiting conditions. Understanding the limitation status of phytoplankton provides critical insight on how to best manage watershed landuse to prevent HABs.
Isabelle Andersen (Primary Presenter/Author), Baylor University, isabelle_andesen1@baylor.edu;
Tanner Williamson (Co-Presenter/Co-Author), Michigan State University, tanner.williamson@gmail.com;
Michael Vanni (Co-Presenter/Co-Author), Miami University, vannimj@miamioh.edu;