Benthic algal community composition of the Laurentian Great Lakes: A qualitative analysis

Excessive growth, associated beach fouling, and other nuisance conditions caused by benthic algae occur globally and, in the Laurentian Great Lakes, have been recognized as issues of management concern since at least the mid twentieth century. Most research on and management of the Great Lakes benthic algal community to date has focused on the genus Cladophora, and work on other benthic algae has been limited. Here, we examine benthic algal community composition in samples collected from two transects in each of Lakes Erie, Huron, Michigan, and Ontario from 2018 to 2023. Our analysis of 337 sampling records shows multiple benthic algal groups contributing to high, potentially nuisance-producing, biomass levels. In addition to abundant Cladophora, we documented charophytes, diatoms, and non-branching filamentous green algae as primary contributors to benthic algal communities, with a biomass at times > 50 g/m² dry weight. Community dominance patterns were generally consistent within a transect when examined by depth or by month, with more within-transect variability in the lower lakes (Erie and Ontario) than in the upper lakes (Huron and Michigan).