Regional, seasonal & depth differences in quagga mussel growth in Lakes Michigan, Huron & Ontario

Session: Cross-lake Comparisons: Frameworks for Understanding Ecosystem Change

Ashley Elgin, NOAA Great Lakes Environmental Research Laboratory, [email protected]
Paul Glyshaw, NOAA Great Lakes Environmental Research Lab, [email protected]

Abstract

The introduction of invasive zebra and quagga mussels (Dreissena polymorpha and D. rostriformis bugensis) has profoundly impacted the Laurentian Great Lakes.  However, we still have much to learn about dreissenid mussel biology, including how environmental conditions influence their growth.  We conducted year-long in situ field experiments in Lakes Michigan (2016-2017), Huron (2017-2018), and Ontario (2018-2019) to measure seasonal quagga mussel growth at multiple depths. Mussels were contained in cages on instrumented moorings at depths of 45m and 90m in all lakes. We found individual growth rates to be strongly influenced by depth, with rates being about twice as high at 45m than at 90m.  Overall, growth rates were higher in Lake Huron than in Lake Michigan; temperature and chlorophyll data provide indications as to why. Surprisingly, a majority of mussel growth occurred following fall turnover and during winter instead of during spring and summer. The conclusion of the Lake Ontario experiment in late spring 2019 will reveal if we find the same patterns as in the other lakes. Ultimately, the results from this study provide useful mussel growth parameters and also help to elucidate the observed population trajectories of quagga mussels in the Great Lakes.