Nutrient and trace metal co-limitation of cyanobacterial blooms in the Great Lakes

Session: Beyond the Edge of the Field: Mitigating the Impacts of Nutrient Pollution on HABs (3)

James Larson, US Geological Survey, jhlarson@usgs.gov
David Costello, Kent State University, dcostel3@kent.edu
Mary Anne Evans, USGS, Great Lakes Science Center, maevans@usgs.gov
Jordyn Stoll, Kent State University, jstoll7@kent.edu
Andrea Fitzgibbons, Kent State University, afitzgib@kent.edu
Sean Bailey, U.S. Geological Survey, sbailey@usgs.gov
Erin Stelzer, U.S. Geological Survey, eastelzer@usgs.gov
Keith Loftin, U.S. Geological Survey, kloftin@usgs.gov

Abstract

Cyanobacterial blooms have increased in extent and severity over the past 15 years in the Great Lakes.  Although cyanobacterial bloom extent is often correlated with spring P loads, associations between cyanotoxin concentrations and environmental conditions have proven elusive.  In lab studies, nutrient stress is often identified as a factor driving microcystin production, the most common cyanotoxin in the Great Lakes. During bloom conditions many elements required for growth reach low concentrations. Some micronutrients (e.g., Fe, Zn, Ni, Mo) form the enzymatic engines that allow producers to access less labile forms of N and P.  Here we report on nutrient enrichment experiments performed in lab and field conditions at several locations in the Great Lakes to assess the potential role of nutrients in limiting growth and microcystin production.  These experiments suggest that nutrients limit both growth and microcystin production, but that while N or P commonly limit phytoplankton growth, microcystin production is often limited by trace metals or is subject to co-limitation.