Submersed macrophyte communities before and after an episodic ice jam in the St. Clair and Detroit rivers

We conducted surveys in 1983 and 1984 of submersed macrophyte communities off six islands in the St. Clair and Detroit rivers using low altitude aerial photography and ground-truth collections. Sample collections in 1984 followed one of the coldest winters on record, during which ice up to 4 m thick developed in areas that were normally ice-free. Growth of many of the 20 taxa collected was delayed in the spring of 1984, as compared with the spring of 1983. By September 1984, however, total abundance of all taxa was equal to or greater than that in 1983. The location, size, and shape of plant beds in September 1984 were similar to those in 1983. We concluded that the unusual ice jam in early spring of 1984 had little, if any, permanent effect on submersed macrophytes in the St. Clair and Detroit rivers.