Environmental Studies of Macrozoobenthos, Aquatic Macrophytes, and Juvenile Fishes in the St. Clair-Detroit River System, 1983-1984: Hoopnet Sampling Record for Macrophytes

This hoopnet sampling record for macrophytes data set was collected for use in the administrative report entitled "Environmental Studies of Macrozoobenthos, Aquatic Macrophytes, and Juvenile Fishes in the St. Clair-Detroit River System, 1983-1984". It is a portion of the data collected for this administrative report, which provided information needed by the U.S. Army Corps of Engineers for preparation of a Supplemental Environmental Impact Statement addressing the winter operation of the lock facilities at Sault Ste. Marie, Michigan, and the subsequent extension of the navigation season in the St. Clair-Detroit River system (SCDRS) to January-February. The following is excerpted from the original report\'s abstract: We describe the distribution and abundance of macrozoobenthos, aquatic macrophytes and juvenile fishes during the 1983 and 1984 open water season, and attempt to predict or evaluate the potential environmental impact of an extended navigation season on the biota of SCDRS. Fauna and flora were diverse and abundant; we identified more than 300 taxa of macrozoobenthos, 30 taxa of submergent and emergent macrophytes, and 36 species of fish. The diversity and abundance of macrozoobenthos were generally highest in the St. Clair River. Abundance and diversity of submersed macrophytes were similar in the two rivers, but Chara dominated in the St. Clair River and Vallisneria americana in the Detroit River. We collected more total fish in the Detroit River but more species in the St. Clair River. Yellow perch and rock bass dominated most catches in both rivers. An ice jam in the St. Clair River in spring 1984 appeared to affect two of the three groups studied--macroinvertebrates and submersed macrophytes. Of the 24 abundant taxa of macroinvertebrates, 9 were seemingly less abundant in spring in 1984 than in 1983 in the St. Clair River; however the densities of 6 of these taxa had recovered by fall 1984 to levels equal to or exceeding those in fall 1983 and the other 3 were within 30% of those in 1983. Cover of the bottom with submersed macrophytes was somewhat reduced in spring of 1984--particularly in the St. Clair River--but recovered to 1983 levels by fall 1984. Plant biomass levels varied between years and locations; no consistent differences could be attributed to the ice jam. Catches of fish were lower in 1984 than in 1983 but differences between locations and months were inconsistent. Observed differences in the plant community could be attributed to reduced temperatures, and ice-scour may have reduced the density of several taxa of macrozoobenthos. Evaluation of the potential environmental impacts of an extended navigation season on the biota of SCDRS was not attempted.