US EPA

2202043 

Journal Article 

Studies on the impact of municipal sewage discharged onto an intertidal area within the Fraser River Estuary, British Columbia (Canada) 

Birtwell, IK; Greer, GL; Nassichuk, MD; Rogers, IH 

1983 

0 

Canadian Technical Report of Fisheries and Aquatic Sciences
ISSN: 0706-6457 

HEEP/84/05208 

0 

1170 

1-56 

English 

HEEP COPYRIGHT: BIOL ABS. A sewage treatment plant at Iona Island (Canada) discharged up to 1.53water, domestic and industrial waste onto the intertidal area of Sturgeon Bank in the estuary of the Fraser River. At low tide the effluent was conveyed across extensive sandflats within a dredged channel which extended 6 km into Georgia Strait. Preliminary studies were carried out to assess the effects of the effluent on water quality, fish survival, distribution and abundance. Fish (7470 comprising 20 spp.) were captured from 11 sampling sites between May 26 and July 2, 1980. Juvenile Pacific herring were numerically dominant in the catch (39%), but juvenile chinook salmon occurred most frequently (20.5%). The intertidal zone near the sewage outfall was underutilized by fish; no salmonids were captured at sites 1 km to the outfall. Significantly more fish (6717) were captured at 4 sampling sites in an unpolluted adjacent area compared with the catches (753) from 7 sites within the area receiving sewage effluent. The survival of juvenile chinook salmon during in situ bioassay experiments increased with distance from the sewage outfall; fish mortality occurred at all experimental sites within 4.4 km from the outfall. Mortality often was rapid and on one occasion all test fish placed 2.2 km from the outfall died within 9 min. The low levels of dissolved O2 which resulted from the discharge of sewage were probably a contributing factor in the mortality of the caged fish. During calm, and warm weather, receiving waters overlying part of Sturgeon Bank became depleted of dissolved O2. This event was often associated with fish stress, mortality and extensive predation by gulls and herons. This frequent mortality of large numbers of fish could have had a deleterious effect on fish stocks in the Fraser estuary. An examination of organic contaminants in fish tissue revealed the presence in flounders and a sculpin of aromatic aldehydes and acids present in municipal wastewaters. These fish also contained a dichloroanisole of uncertain origin and persistence. A number of chlorinated hydrocarbon pesticides, PCB (polychlorinated biphenyl) and chloro- and nitrophenols were detected at trace levels in a sample of flounders taken in 1978. Several volatile organic compounds, chiefly solvents, were measured in seawater samples in the area of the outfall. These substances were present at concentrations well below their incipient lethal levels.