Benthic invertebrates in selected streams of the Piceance Creek basin, northwestern Colorado, water years 1977-81

Data from the periodic collection of benthic invertebrates at six streamflow stations in the basin during water years 1977-81 are presented and summarized. A total of 162 genera from 8 insect orders and 8 non-insect orders were documented. Numbers of organisms per sample ranged from 0 to 3,700. Counts generally were greater during low streamflow. Diptera (two-winged flies) were the most numerous organisms and the percent composition of Diptera increased downstream. Organisms associated with both unpolluted and polluted streams were collected. The assignment of taxa into trophic groups placed most taxa into the burrowers-sprawlers-clingers (habits) groups and primary and secondary consumer (food-web) groups. General community structure, however, remained balanced and stable. Mean diversity indices ranged from 2.21 to 2.82 and similarity indices indicate better than 50% consistency of composition. Mean diversity indices were greatest in the middle part of the Piceance Creek basin. The distribution of benthic invertebrates collected indicated that no deleterious water quality conditions existed during the study period. Differences in benthos communities within and between sites are attributed to differences in water discharge, water temperature, substrate, and chemical quality of water. (USGS)