Long-term dynamics of the Lake Huron benthic community

Analysis of Lake Huron's benthic community structure from the 1950s to 2022 provides a long-term perspective on the effects of environmental change on the benthic community and the potential for ecosystem recovery. The lake's four major basins differ markedly in benthic community composition and abundance, as well as in the environmental drivers shaping these assemblages. In Saginaw Bay, major shifts corresponded to periods of eutrophication, subsequent improvements in water quality, and the introduction of Dreissena. The mayfly Hexagenia , common in 1954, was nearly extirpated in the 1960s–1980s, while densities of pollution-tolerant species increased. Partial recovery of the Saginaw Bay benthic community began in the 1990s, characterized by declining oligochaete abundances, increasing chironomid densities, and, since 2017, further gains in both density and diversity across multiple taxa. In contrast, the main basin of Lake Huron and Georgian Bay were historically dominated by Diporeia , which nearly disappeared following zebra ( D. polymorpha ) and, especially, quagga ( D. rostriformis bugensis ) mussel invasions in the 1990s–early 2000s. In the North Channel, Diporeia declined after 2002 despite low dreissenid densities, and this decline was accompanied by an increase in chironomid abundance. Across all basins, quagga mussels have become a key component of benthic communities, with densities highest in the main basin and lowest in the North Channel.