Long-Term Impact of Dredged Material at two Open-Water Sites: Lake Erie and Elliott Bay. Evaluative Summary

摘要

The Lake Erie study area included two control and three disposal sites, sampled once in 1979. Disposal sites contained more gravel and sand compared to control areas. Numerous macrofaunal and meiofaunal animals were found at all of the sites. In general, control sites contained more macrofaunal animals and species while the disposal sites were richer in meiofaunal. Substrate type and variety, which was influence by the disposal events, determined which animals were found where. None of the sites were devoid of animals and there was no indication that sediment contaminants affected benthic communities at the disposal sites. There were no difference in mercury or cadmium concentrations in sediment samples from the various sites. Samples taken at the Elliot Bay disposal site revealed that the disposal mound, created in 1975-1976, was still present and had stabilized physically and chemically. The mound area contained more animals that the surrounding bottom areas. Bivalves and polychaetes were the dominant animals than the surrounding disposal site. The numbers of these animals at the site increased from 1976 to 1979-1980. Sediment at the center of the disposal site contained polychlorinated biphenyls (PCB); however, other areas of Elliot Bay, removed from the dredges material mound, also contained PCB at concentrations similar to those observed at the site. Some animals taken from the disposal mound contained PCB at levels slilghtly higher than sediment levels which were in the 2.0- to 3.0-ppm range.