Plankton in the lower Grand River at Lowell, Michigan, 2001-2002.

Abstract

The Grand drains much of southern Michigan, touching as far east as Washtenaw County. 2001-2002 was very nearly a record snow season at Grand Rapids with considerable periodic thawing. Thirty-four plankton drags were performed from October to June from bridges above and below the confluence of the Flat River. There was no real difference above or below the Flat over the months, no one family represented to the substantial exclusion of others. Of bacillariophytes, the most numerous pennates were Navicula, almost all small, but Asterionella formosa was well represented. The most numerous centric were Melosira varians chains. In other algae, Coelastrum microporum was ubiquitous, while several species of Pediastrum appeared. Chlorophytes were very rare, while cyanophytes also presented very few specimens. Zooplankton were not numerous, by slight preponderance the Keratella, but with a respectable variety of genera. Large zooplankters were very rare, most of which were long dead. The phytoplankton and zooplankton of these samples were not markedly different from the results of workers in Michigan and elsewhere going back a century.