The benthic fauna of 41 acid sensitive headwater lakes in North Central Ontario

The pH of the lakes, located in 6 districts of Ontario, ranged from 4.6 to 7.7. Analysis of midlake benthic fauna detected no relationships between total benthic abundance, dry biomass or diversity, and lake pH or alkalinity. There was greater variability within the lakes of each district or pH category than there was between pH categories. Slight changes in the composition of Chironomidae were observed in the pH categories, with the relative proportions of the Tanytarsini subfamily and the Chironomus salinarius group decreasing with decreasing pH, while the proportion of the C. anthracinus group increased. However, these differences were not significant beyond p less than 0.2. This study indicated that sediment percent organic content had a greater influence on the benthic fauna than did alkalinity or lake pH.