Analysis of Planktonic Rotifer Assemblages from Sudbury, Ontario, Area Lakes of Varying Chemical Composition

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Abstract
Planktonic rotifer samples were collected from 47 Sudbury, Ontario, area lakes to determine factors influential to species distributions. The lakes ranged from highly acidic and metal contaminated to circumneutral with low metal concentrations. Median rotifer abundance was substantially higher in non-acid (pH > 5.2) than in acid (pH < 5.2) lakes, although differences in species distributions were evident. Application of detrended correspondence analysis to rotifer species densities revealed broad separation of communities from acid and non-acid lakes. Assemblages from acid lakes were highly similar in species composition and dominance, while those from non-acid lakes were generally much more heterogeneous. It was hypothesized that planktonic rotifer communities converged in species composition as a consequence of the stress of lake acidification, in a pattern similar to that previously described for planktonic crustaceans. Among the best predictors of rotifer community composition were lake pH and the concentrations of manganese and aluminum.