Nitrogen limitation of algal biofilms in Lake Superior coastal wetlands

Session: Poster Session

Aletha Hefko, Mary Griggs Burke Center for Freshwater Innovation, Northland College, [email protected]
Michele Wheeler, Wisconsin Department of Natural Resources, [email protected]
Matthew Cooper, Northland College, Mary Griggs Burke Center for Freshwater Innovation, [email protected]

Abstract

Coastal wetlands are among the most productive habitats in the Laurentian Great Lakes and provide many important ecosystem services including fish spawning areas and migratory bird habitats. The influence of nutrient loading to these systems from watershed land use is generally understudied. As anthropogenic nutrient loading can alter the macronutrient that limits primary productivity in wetlands, understanding nutrient limitation patterns can provide insight into potential nutrient-related impacts. Lake Superior has a lower level of anthropogenic development and colder waters than the other Laurentian Great Lakes, both of which limit productivity and nutrient availability within these coastal wetlands. We used algal biofilm chlorophyll-a accumulation on nutrient diffusing substrates (NDS) to determine nutrient limitation within coastal wetlands on the Bayfield peninsula, Apostle Islands, and in the St. Louis estuary. Within a mainland coastal wetland, we placed distributed nutrient diffusing substrata to investigate intra-site variability. Preliminary results suggest that biofilm communities in southwestern Lake Superior coastal wetlands are nitrogen limited in general and that variation occurs within wetlands based on water source. This follows expected patterns and indicates that unregulated nitrogen runoff could cause significant changes in the primary productivity of coastal wetlands, which could have significant impacts on Great Lakes food webs.