Beyond the nearshore shunt: Quagga mussels boost benthic-pelagic nutrient exchanges in Lake Michigan

Session: Poster Session

Vadym Ianaiev, University of Minnesota Duluth, [email protected]
Jiying Li, University of Minnesota Duluth, [email protected]
Audrey Huff, University of Minnesota Duluth, [email protected]
John Zalusky, University of Minnesota Duluth, [email protected]
Tedy Ozersky, Large Lakes Observatory, University of Minnesota Duluth, [email protected]
Sergei Katsev, Large Lakes Observatory, University of MN, [email protected]

Abstract

By early 2000s, quagga mussels (Dreissena rostriformis bugensis) spread offshore in Lake Michigan-Huron, yet little is known about their impact on benthic nutrient cycling. We investigated the cycling of carbon and nutrients in the offshore and nearshore sediments using sediment incubations and vertically-resolved geochemical profiling. Results suggest that mussels drastically amplified material exchanges between sediments and the water column. By sequestering particulate carbon and nutrients from the water through filter-feeding, mussels increased sedimentary carbon mineralization rates, decreased oxygen penetration, and increased nutrient fluxes both in and out of the sediment. In Green Bay, mussel-colonized sediment patches uptake nitrate at four times the rate in mussel-free patches, uptake sulfate at six times the rate, and release soluble reactive phosphorus (SRP) at twice the rate. SRP excretion by mussels themselves was four times higher than SRP effluxes from mussel-free sediments. In well-oxygenated offshore sediments, mussel coverage correlated with higher nitrate effluxes from sediments, presumably because of oxidation of increased amounts of ammonium.  These enhanced exchanges suggest that the Dreissena have increased the significance of benthic processes in the lake’s carbon and nutrient budgets. The specific effects on benthic fluxes differ between the lake’s nearshore and offshore areas and require further quantification.