Benthic Communities in Five Major Rivers of the Hudson Bay Lowland, Canada

A total of one hundred and twenty six species of macroinvertebrates were collected from five major Ontario rivers (Moose, Albany, Attawapiskat, Winisk and Severn) of the Hudson Bay Lowland. Benthic communities in all rivers were dominated primarily by chironomids and oligochaetes except in the East channel of the Moose River where gastropods were also a common taxon. Diversity, as measured by both species richness and the Shannon-Weiner index, was not significantly different in each river. Species distribution was related to substrate composition, river velocity and depth at each station. Community similarity analysis showed that rivers geographically closest together, sharing common flow directions and similar drainage basins resembled each other most in terms of benthic communities. The exception to this was the East channel of the Moose River which showed little resemblance to the other Lowland rivers studies. This was attributed to the highly channelized nature of the Moose River and the origin of the East channel itself which is fed by waters draining the Clay Belt, a unique subprovince of the Canadian shield.