Modeling the influence of invasive mussels on phosphorus cycling in Lake Michigan

Session: Mud, Macrofauna and Microbes: Benthic Organism-Abiotic Interactions at Varying Scales (3)

Qian Liao, University of Wisconsin-Milwaukee, [email protected]
Harvey Bootsma, University of Wisconsin-Milwaukee, [email protected]
Chunqi Shen, University of Maryland Center for Environmental Sciences, [email protected]

Abstract

The impact of benthic invasive mussels on phosphorus dynamics was investigated by a three-dimensional physical-biogeochemical model in this study.  The physical model was validated against a good range of field observations. The biogeochemical NPZDG model successfully reflects the spatial and temporal variations of dissolved phosphorus (DP) and particulate phosphorus (PP). For comparison, cases without mussels was also simulated to examine mussels’ impact on phosphorus cycling. Model results showed a significant reduction of phytoplankton in the nearshore area (depth < 75 m) where high density of mussel colonization was found, and a higher concentration boundary layer for increased DP was indicated by the model. An increased DP to PP ratio in the hypolimnion was also noted, especially during the stratified summer. Model results suggested an increase delivery rate of PP in hypolimnion due to mussels’ filtration, and the effective flux was 11.5 times greater than the passive settling rates at the mid-depth site. According to model results, while the nearshore is a net source of PP to the offshore, mussels could reduce the PP transport to the offshore region by 25%. This analysis underscores the important role of mussels in Lake Michigan and could be instructive for the lake-wide phosphorus management.