Great Lakes coastal waters and shorelines experience sporadic but concerning overgrowth and washup of benthic algae. These events can lead to nuisance conditions and ecosystem impairment. Coastal research and management of benthic algae have often focused on specific genera, often Cladophora sp. and Lyngbya (Microseira sp.), that were perceived to be problematic. However, we have observed multiple other algal groups in benthic samples and incidental observations of shoreline washup. I will present a summary of observations since 2018 of benthic algal community composition at nearshore sites in Lakes Michigan, Huron, Erie, and Ontario. Preliminary results indicate that Cladophora sp. was found at all locations sampled but was not always dominant. Stalked diatoms and Chara sp. were consistently found, and sometimes dominant, at various sites in Lakes Michigan and Huron. Non-branching filamentous green algae were frequently found in Lakes Erie and Ontario and sometimes rivaled Cladophora sp. in relative contribution to algal biomass. Multiple algal groups contributed to elevated, potentially nuisance producing, biomass. Increased understanding of the prevalence and nuisance potential of various benthic algal groups can guide research and modeling of the physiological (light and nutrient) conditions that lead to algal overgrowth. This work supports ecosystem status assessments and decision making around nutrient targets to support desired algal levels.
