Particulate nutrient stoichiometry in Great Lakes seston: Are there dominant drivers?

Ratios of Carbon (C),Nitrogen (N),and Phosphorus (P) in offshore particulate matter can be used as indicators of nutrient limitation in phytoplankton and inform on the condition of the lower food web. While seston C:N:P stoichiometry affects ecological processes and food web function, there is limited understanding of the environmental drivers of particulate C:P and N:P variability in freshwater lakes. Lab-based experiments have assessed the role of phytoplankton stoichiometric drivers, but no studies have used long term observational data to assess the impacts of those drivers on offshore planktonic stoichiometry across the North American Great Lakes. We use phytoplankton, total nutrient, and particulate nutrient data collected by the Environmental Protection Agency’s Great Lakes National Program Office from 2001 – 2019 to investigate the relationship between environmental drivers and particulate C:N:P across all five Great Lakes. Drivers include proportions of major phytoplankton groups, total and dissolved phosphorus concentrations, and total oxidized nitrogen concentrations. Across all lakes, the strength of most relationships between potential drivers and particulate N:P and C:P were weak. In some instances, the correlations found in this long-term data were contradictory to previously observed correlations in lab and experimental lake-based studies. Our results highlight the complexity of the relationship between environmental conditions and the nutrient status of the Great Lakes lower food web, emphasizing the continued need for surveillance of offshore conditions.

Primary Presenter: Erica Yang, U.S. EPA Great Lakes National Program Office (yang.erica@epa.gov)

Authors:

Erica Yang, U.S. EPA Great Lakes National Program Office  (yang.erica@epa.gov)

Annie Scofield, U.S. EPA Great Lakes National Program Office  (scofield.anne@epa.gov)

Euan Reavie, University of Minnesota Duluth – Natural Resources Research Institute  (ereavie@d.umn.edu)