Dominant Planktonic Rotifers of Major Waterways of the United States

Rotifers were the most numerous metazoans found in preserved plankton samples taken routinely at 128 sampling stations on the major rivers and Great Lakes of the United States. While rotifers of more than one genus often dominated a sample, the dominant form tended to be one species. Generally, stations with high population densities had low species diversity. Turbulence, silt, and some other edaphic factors appeared to be more important than industrial or domestic wastes, during winter and early spring, in reducing the number of species of rotifers in the biota. During the summer and fall, differences in the abundances of dominant species appeared to be the best criterion for indicating differences in water quality or pollution.