Microcrustacea from the Benthos of Nine Minnesota Streams

Abstract

The occurrence and microdistribution of microcrustaceans in nine low order Minnesota streams were examined. Total densities ranged from 16,652 to 430,863/m². Eight species of cyclopoid copepods, 13 species of canthocamptid harpacticoid copepods, and one parastenocarid harpacticoid copepod were identified. Nineteen species of cladocerans were collected. Ostracods were quantified but not identified to species. Cyclopoid copepods were most abundant in slow water habitats where the majority lived on the sediment surface; in some cases they occurred in well sorted gravel or pea gravel, and were likely living interstitially. Harpacticoid copepods were most common in coarse sediments with a sand matrix, but occurred in all benthic habitats. Cladocerans included the Daphnidae, Macrothricidae, Bosminidae, and Chydoridae and were most abundant in slow water habitats of the stream; chydorids were the most common, reaching densities of over 25,000/m².