Dreissenid mussel distribution in Georgian Bay is limited by lateral mixing of chemical gradients

Session: 48. - Physical Ecology in Large Lakes and their Watersheds

Lakshika Girihagama, University of Toronto, [email protected]
Mathew Wells, University of Toronto Scarborough, [email protected]
Todd Howell, Ontario Ministry of the Environment, Env. Monitoring & Reporting Br, [email protected]

Abstract

There are gradients of conductivity and nutrients in the coastal zone of Eastern Georgian Bay that appear to limit the spatial distribution of mussels. Rivers flowing into Georgian Bay from the Canadian shield are relatively low in conductivity compared to the main body of Lake Huron, and so there is an observed gradient of salts reminiscent of a well-mixed estuary near the river mouths. In order to understand the hydrodynamics of these fresh estuaries, we present modelling results using a conceptual one-dimensional model and a more complex three-dimensional hydrodynamic simulation (FVCOM) to show the mechanisms that may be responsible for calcium limitation in the nearshore mussel distribution. Both our simple and complex models show that the mixing length-scale of low conductivity waters from rivers can be described in terms of geometry, eddy diffusivity, and the river volume flux. The mixing scale is in the range of 1-10 km across the seasonally stratified and barotropic coastal waters in the Eastern Georgian Bay. We will present results from tracer release numerical experiments in FVCOM to track transport and dispersion river waters. In addition to discussing mussel distribution, we will discuss the role of hydrodynamics in setting near-shore nutrient gradients. 

1. Keyword
hydrodynamic model

2. Keyword
Georgian Bay

3. Keyword
estuaries

4. Additional Keyword
dreissenid mussels