Biological assessment of Cannon Creek, Missouri by use of emerging chironomidae (Insecta: Diptera)

A biological assessment was done to determine the impact of heavy metal discharge from the Schuykill Metals Recycling Plant (SMCP) on Cannon Creek, Missouri, its receiving stream. The relationship between sediment chemistry and chironomid emergence was examined. Twenty-four heavy metals and nutrients from the SMCP discharge effluent were examined in Cannon Creek from above the effluent, at the effluent, and below the effluent. Five heavy metals (barium, cadmium, lead, manganese, and zinc) and sodium varied significantly between sites. Changes in community composition, mean abundance of emerging chironomids, and Kansas Biotic Index Values were used to detect impairment by heavy metals and nutrients in Cannon Creek. Concentrations of lead and zinc in Cannon Creek were at levels potentially lethal to chironomids, yet mean abundance of emerging chironomids actually increased with the increase of heavy metals and nutrients and showed a strong and positive correlation with barium and sodium, and a weaker correlation with increases in lead and cadmium. Chironomid diversity patterns did not correlate with the concentrations of heavy metals in Cannon Creek. Community similarity between sites was greatest between the reference site and the site at the SMCP discharge effluent. Low similarity between sites was attributed to gross changes in stream morphology rather than to any effects from the SMCP effluent. Finally, the KBI tolerance values to heavy metals for chironomids in Cannon Creek were above those encountered in the reference condition for the Western Combelt Plains Ecoregion, indicating minimal impairment.