Distribution and Abundance of Tubificid (Oligochaeta) Species in Toronto Harbour, Lake Ontario

Abstract

The tubificid oligochaetes build up populations in excess of 200,000/m 2 in Toronto Harbour. Pollution-tolerant species in great abundance are located around the mouth of the Don River, whereas small numbers and some less tolerant species are found near the island shores. There is no evidence of diurnal rhythms in the vertical distribution of the worms in the sediment. Dry weights for tubificids are about 16% of the wet weight for fresh-starved worms. The ash content averaged 34% of the dry weight for worms with a gut full of mud, but 11% for worms clear of gut contents.