Nutrient and trace metal impacts on Great Lakes algal growth and community composition

Session: Harmful Algal Blooms: From Ecosystem Drivers to Ecosystem Impacts (3)

Jordyn Stoll, Kent State University, [email protected]
David Costello, Kent State University, [email protected]
James Larson, US Geological Survey, [email protected]
Andrea Fitzgibbons, Kent State University, [email protected]

Abstract

Efforts to reduce the frequency and extent of harmful algal blooms (HABs) require knowledge about factors that control algal growth, toxin production, and the community shift to cyanobacterial dominance. While labile N and P fuel primary production, micronutrients play a lesser-understood role as the enzymatic engines that promote rapid and efficient growth and toxin production. Just as algal communities shift seasonally, nutrient and trace metal availability can shape community composition by selecting for specific species. In summer 2017, we completed a mesocosm nutrient enrichment experiment using water collected from four river mouths in Lakes Michigan and Erie. Nutrient treatments were fully factorial and completed in triplicate, including phosphate, ammonia as N, and trace metals (Fe, Zn, Ni, Mo, Mn). Community composition (counts), chlorophyll-a and microcystin production (ELISA) were quantified for each bottle. Preliminary data suggest that microcystin concentrations in algae are decoupled from biomass response to enrichment, and that nitrogen and trace metal addition increases Microcystis spp. abundance. These data demonstrate that a multi-nutrient view of elemental requirements is needed to understand the drivers of HABs in the Great Lakes.