Correlation between microcrustaceans and environmental variables along an acidification gradient in Sudbury, Canada

Multivariate methods were used to relate microcrustacean (pelagic and litto ral) richness and composition (presence/absence) to water quality and other environmental variables. All acidification variables (pH, aluminium, ANC) showed significant correlation with both species richness and composition. The variation in microcrustacean richness was best explained by the combina tion of dissolved organic carbon (DOC), fish species richness and lake area . Of 16 variables tested, pH showed strongest correlation with the main gra dient in the crustacean composition explaining between 13 and 16% of the va riance in the species data (CCA). pH, elevation, lake area, average depth, DOC, conductivity and fish species richness explained 30-54% of the total v ariance. Stronger correlation was obtained between species composition and environmental data in analyses which included the between-year differences than analyses based on the cumulative species records. Analyses based on th e pelagic species exclusively gave similarly stronger correlation than anal yses based on all crustacean species. Small changes in the species composit ion during the three years of study may be an indication of recovery of mic rocrustaceans in Killarney lakes.