Variation in standing crop and species composition with stream reach, colonization time, and habitat on the Maple River, Emmet County, Michigan, USA.

Abstract

Aquatic invertebrates drift from one location to another in order to find more suitable habitat, food, or escape from predation. Our objective in measuring the colonization of aquatic invertebrates was to test whether these are constant over time. We choose two sites, above and below a dammed lake on the East Maple River, and three locations within those sites, main current shade, main current sunny, and deadfall area. Three lidded baskets with five rocks within them were buried at each location. Weekly one basket from each location was removed and invertebrates tallied for three weeks. The water chemistry tests performed at each site were extremely similar. General trends observed show that the invertebrates prefer the upstream site over the downstream site possibly due to the slower current upstream allowing the organisms to drop out of the water column into the baskets. The sunny habitat apparently was chosen most often perhaps because of higher primary production. The family Simuliidae comprised the greatest proportion of organisms overall. This may be due to no preference of location selection by the Simuliids. Three weeks of data is not enough to fully develop these hypotheses, but it appears that there are different colonization time scales for each of the sites for unknown reasons.