The effluent stream of the Cardinal Plant coal fly ash pond in eastern Ohio was characterized by less diverse habitat and food resources and a less complex substratum compared with an adjoining stream unaffected by the effluent, and supported a less diverse macroinvertebrate fauna dominated by physicochemically tolerant, fine particle-consumers. A sampling site in the unaffected stream contained large numbers of shredders and generally exhibited greater macroinvertebrate abundance than two sites in the effluent.