Benthic Macroinvertebrate Changes in Lakes near Sudbury, Ontario, following a Reduction in Acid Emissions

Abstract

Benthic macroinvertebrates were sampled from three lake basins before and after a reduction in acidity, a result of reduced acid emissions from the smelting industry in Sudbury, Ontario. The number of taxa and macroinvertebrate density were greater in the later surveys of the lakes than expected by chance alone. Species richness and macroinvertebrate density were higher in all littoral habitats and in profundal habitats of two lake basins. Species richness showed little change and macroinvertebrate density was lower in the profundal habitat of the third lake basin. Increased survival, probably as a result of reduced chemical toxicity, best accounted for the higher species richness and benthic density. Trout predation, through a numerical response, probably masked these responses in the profundal habitat of the third lake basin because the refuge area from predation (i.e. region of the hypolimnion low in dissolved oxygen) was small. These data indicate that biological recovery of industrially acidified lakes is possible solely by reducing emissions, provided that recolonizing species are not locally extinct.