Final Report: Status Macroinvertebrates in the Lake Ontario

Abstract

The benthic macroinvertebrate community of Lake Ontario continues to change in nearshore and offshore areas. In 2008, Diporeia is very rare throughout the lake at all depths. There were only four of 52 locations where the densities were greater than100 m-2. The maximum density of Diporeia in 1994 and 2008 was13,280 m-2 and 248 m-2, respectively. Dreissena continues to be an important member of the benthic macroinvertebrate community. Dreissena is more abundant in deeper waters (greater than 90 m) in 2008 compared to 2003 but lake-wide density appears to be declining in sediments less than 90 meters between 2003 and 2008. Fingernail clams (Sphaeriidae) are less abundant between 1994 and 2008 while worms (Oligochaeta), and midge larva (Chironomidae) densities remain constant.