A critical review of the effects of turbidity on aquatic organisms Vohs, P. A., I. J. Moore, and J. S. Ramsey. 1993. A critical review of the effects of turbidity on aquatic organisms in large rivers. Report by Iowa State University, Ames, Iowa, for the U.S. Fish and Wildlife Service, Environmental Management Technical Center, Onalaska, Wisconsin, March 1993. EMTC 93-S002. 139 pp. (NTIS # PB94-110228) ABSTRACT The U.S. Fish and Wildlife Service (FWS) has a leading role in promoting the monitoring and analysis of environmental trends in the Upper Mississippi River System (UMRS). A thorough review of government reports on navigation effects on biota of the UMRS was conducted by Rasmussen (1983). He pointed out that numerous data gaps remain, both on the physical effects of navigation on the river, its banks and backwaters, as well as on responses of aquatic biota to environmental change associated with navigation effects. Prominent among variables impacting riverine biota is increased turbidity from navigation- induced sediment resuspension and bank slumping. Of special concern are the potential effects of sediment on vegetated backwater habitat. The FWS, recognizing the need to examine all environmental aspects of turbidity generated by navigation, agricultural practices, and other activities, contracted a literature survey in September 1988 on the effects of turbidity on the biota of large rivers. Goals of the proposed work were to (1) carry out a literature review on biological effects of suspended sediments (including turbidity, washload, and filterable solids); (2) identify data gaps relating to freshwater ecosystems; and (3) recommend priority research on the biological effects of suspended solids and turbidity in the Upper Mississippi River System. This report presents efforts toward meeting Goal 1 of the proposed work. KEYWORDS Upper Mississippi River, suspended sediments, biological effects, freshwater ecosystems, suspended solids and turbidity