The Impact of Oil on Marsh Communities in the St. Lawrence River

Abstract

A 2-year investigation of fish and waterfowl populations was conducted on St. Lawrence River marshes that had been polluted with No. 6 industrial fuel on June 23, 1976. The heavy oil, which penetrated as much as 5 meters into the dense cattail stands, was removed along with the oiled vegetation. This was a zone of intense animal activity and mortality was great during the first few weeks. Marshes having different levels of oiling were selected for study along with a control area because prior baseline data were not available. The results suggested but could not prove that there was some long-range effects of the oil on these marsh communities. An example is the possible loss of eggs and larval fish for some species. However, the effects of the oil generally were masked by the effects of natural factors, and therefore difficult to identify or quantify. Variables such as water leve, time of year, water temperatures, type of oil, physical arrangement of the marshes, and the cleanup process each had an important role in the overall impact. The study demonstrated that the dynamic nature of marsh populations and communities make it imperative that the ecology of sensitive areas be studied in advance os that meaningful assessments can be made on a long-term basis. It also pointed out the danger of misinterpreting changes observed as being due to oil when in reality many interrelated natural factors are having their effects on populations and communities at the same time.