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Physical circulation in the coastal zone of a large lake controls the benthic biological distribution.
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  • Lakshika Girihagama,
  • Todd Howell,
  • Mathew Wells,
  • Jingzhi Li
Lakshika Girihagama
University of Toronto

Corresponding Author:lakshika.rwrh@utoronto.ca

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Todd Howell
the Ontario Ministry of the Environment and Climate Change (OMOECC)
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Mathew Wells
Univeristy of Toronto
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Jingzhi Li
University of Toronto
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There are gradients of conductivity and major ions in the coastal zone of the Eastern Georgian Bay of Lake Huron that appear to limit the spatial distribution of invasive dreissenid 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 solutes near the river mouths. The field observations show a strong positive correlation between conductivity and calcium concentration. Thus, we use conductivity to infer the solute concentrations required for the successful growth of dreissenid mussels. We observe most mussels in regions where specific conductivities were greater than 140 mS/cm. We use field observations to examine how the low calcium river water mixes within the coastal zone, which sets solute gradients that determine mussel distribution. When river flows are low, there is only a weak solute gradient across the coastal zone, implying an intrusion of open bay waters into the shallow embayments that is favourable for the growth of mussels. In contrast, when river flows are as much as 10 times higher, there is a strong solute gradient that extends further towards the lake, and the low calcium appears to inhibit and limit the growth of dreissenid mussels. Thus, the seasonal character of solute gradients helps describe the spatial distribution of dreissenid mussels and helps explain the localized absence of a species that is otherwise prevalent in much of the Laurentian Great Lakes.
Mar 2022Published in Water Resources Research volume 58 issue 3. 10.1029/2021WR030412