18. Lessons from Bioinvasion of Lake Champlain, U.S.A.

Freshwater lakes provide ideal habitat for invasive species, such as the zebra mussel, which can weaken lake ecological integrity by altering food web structure and dynamics. This case study utilized 23 years Lake Champlain data to examine relationships among water quality, invasive species, native mysids (Mysis diluviana) and the zooplankton community. Canonical correspondence analysis (CCA) was employed to ordinate and qualitatively assess long-term patterns across the datasets, and the hybrid evolutionary algorithm (HEA) revealed quantitative relationships and thresholds. Results from both methods are complementary and suggest that: (1) zebra mussels directly affect rotifer densities by preying on slow moving rotifers, and (2) zebra mussels indirectly affect cladocerans, copepods and mysids by both preying on rotifers and grazing on phytoplankton. The direct and indirect effects of zebra mussels on the zooplankton community as well as on mysids adversely affect the ecological integrity of Lake Champlain. Data ordination by CCA and inferential modelling by HEA proved useful for elucidating long-term food web patterns in the complex Lake Champlain ecosystem.