ZOOPLANKTON SPECIES ASSOCIATIONS IN QUEBEC LAKES - VARIATION WITH ABIOTIC FACTORS, INCLUDING NATURAL AND ANTHROPOGENIC ACIDIFICATION

Abundances and biomass of 38 zooplankton species and accompanying abiotic data from 54 Quebec lakes were subjected to cluster and correlation analysis to determine 1) characteristic zooplankton associations of cooccurring species, 2) relative importance of abiotic variables in lake typology, and 3) relationships between the integrated environmental factors derived from lake morphometry, water quality, and acidification level, and the structure of zooplankton communities. The 8 groups of species identified in the cluster analysis may be considered separate "species associations' characterized by distinct patterns of distribution. Differences in mean pH and sulphate concentrations can be detected between groups of lakes representing the different species associations. Factor analysis produced 7 factor scores which explain 82% of the total variance of the morphological, physical and chemical variables. The distribution pattern of acidity or alkalinity represents the major feature in water chemistry variation, but lake morphology also account for the observed environmental variability. Community structure, whether expressed in size classes or in trophic groups, tend to vary among sets of lakes of different pH. -from Authors