Benthic shunt: Dreissenid mussels now control phosphorus dynamics in Lake Michigan

Session: Nutrient Sources, Transport, and Internal Cycling (1)

Jiying Li, University of Minnesota Duluth, [email protected]
Vadym Ianaiev, 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

Dreissenid mussels have been re-engineering various ecological processes in the Great Lakes since the late 1980s, leading to a decline in pelagic primary productivity. The magnitude of dreissenid effects on the benthic fluxes and lake-wide dynamics of phosphorus, the limiting nutrient in the Great Lakes, however, has not been well quantified. We analyzed the dynamics of total phosphorus (TP) in Lake Michigan using a whole-system mass-balance model that includes dreissenid populations. The model suggests that prior to the dreissenid invasion, TP concentrations in Lake Michigan were controlled by the balance between external input and sediment burial. On the other hand, presently TP concentrations are regulated by mussel activities, including feeding, excreting, and egestion. Filter-feeding removes significantly more TP from the water column than normal sedimentation, and benthic P recycling fluxes are now dominated by mussel egestion and excretion, which are an order of magnitude higher than direct fluxes from sediments and an order of magnitude higher than external inputs. The continued expansion of quagga mussels into deeper waters is predicted to lead to a further decline in lake-average TP, approaching a limit value of around 1.4 ?g/L.