An aquatic biological survey was conducted in 1979-1980 to determine the effects of drainage from an active coal strip-mine on Trout Creek, in northwest Colorado, U .S .A . Sampling was conducted over four seasons at four stations for periphyton, benthic invertebrates and fish . Periphyton in Trout Creek changed in the relative abundance of algae divisions in no apparent relation to mining . Diatoms were the predominant division at all sites . Golden-brown algae were abundant in spring at the stations upstream and adjacent to the mine . Blue-green algae were relatively important at stations upstream and downstream of the mine in winter . Benthic invertebrates exhibited a progressive increase in density, biomass and number of taxa from the upstream station to the downstream station . Shannon-Wiener diversity index for bethic invertebrates decreased slightly downstream of mine drainage but remained indicative of a clean water community .
Aquatic insects (especially Trichoptera) were the predominant invertebrates at all stations . Analysis of functional groups of benthic invertebrates revealed increased importance of collector species at the lower sites while shredders were most important upstream of the mine . Unlike the invertebrates, fish exhibited slightly lower biomass at the station adjacent to the mine . The decrease was due to fewer salmonids . However, salmonid density and biomass increased substantially at the station just downstream of the mine . Non-game species (suckers and minnows) increased in numbers downstream and were most abundant at the lowest station . This coal strip-mine had little discernable adverse effects on the periphyton and invertebrates of Trout Creek . Fish populations did not appear to be significantly affected by the mine . Apparently, the presence of settling ponds and a buffer zone of unmined land between the mine and the stream helped to minimize adverse effects .