Why does Cladophora fail to reach nuisance proportions in Lake Simcoe?

Abstract

In recent years, a resurgence of filamentous benthic algae (e.g., Cladophora) in the Laurentian Great Lakes has been perceived as a consequence of dreissenid mussel invasion and subsequent alterations to ecosystem nutrient and energy cycling. Here, we employ high-frequency hydro acoustic surveys at two sites in Lake Simcoe to assess the presence and extent of excessive benthic algal ( Cladophora) growth that we hypothesized would be growing on hard substrate in the post dreissenid mussel period. Despite comparable dreissenid abundance, water clarity and phosphorus concentrations to sites in the lower Great Lakes known to suffer extensive Cladophora fouling during the summer months, the nuisance growths of Cladophora that have become a seasonal phenomenon in the lower Great Lakes were not found at survey sites in Lake Simcoe. While the proximal cause for the lack of excessive Cladophora growth in Lake Simcoe remains elusive, in this paper, we highlight some distinct differences in environmental conditions and ecological interactions that might make near shore areas of Lake Simcoe unique from near shore areas of the lower Great Lakes. Overall, the results of this study and other recent studies in Lake Simcoe are not inconsistent with the near shore shunt hypothesis that predicts dreissenid mussels enrich the benthic environment, but the manifestation in Lake Simcoe is very different than that observed in the lower Great Lakes.