Add to ORKGThe bottom fauna and related ecological factors were investigated in a bay of Lake West Okoboji, Iowa, during the summer of 1959. Two contiguous areas were compared: (1) a relatively small, shallow bay largely enclosed by land and partially separated by a narrow sand spit from (2) a larger, deeper bay opening into the major lake basin. Data include particle size analysis and organic content of substratum, and qualitative and quantitative distribution of more than 50 species of macroscopic bottom animals. Density and bio-mass of animals were calculated at 14 stations. Chironomids (Diptera) were the dominant group in the study area. Distribution of chironomid genera, as well as of other invertebrate groups, was found to be related to depth, v...