Impact of Midnight [sic] Mine Drainage on the Benthic Macroinvertebrate Community in Blue Creek

Download or read book Impact of Midnight [sic] Mine Drainage on the Benthic Macroinvertebrate Community in Blue Creek written by Stefan H. Cairns and published by . This book was released on 1988 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The objective of this study was to describe and quantify the impact of the Midnite Mine on the benthic macroinvertebrate community of Blue Creek. Macroinvertebrate samples were collected upstream and downstream of the entry of the mine drainage throughout 1987. The sampling scheme was designed to identify the linear impact of the mine drainage by analyzing the invertebrate community in terms of density, diversity, similarity, presence- absence, and number of taxa. Seasonal and annual trends were determined by comparison of sample dates and by comparison of the previous investigations in the same system. The mine drainage reduced the macroinvertebrate density by 85 percent on a seasonal average immediately downstream of the mine drainage entry. The degree of impact was consistently high for all five sample dates and ranged from 76 percent to 94 percent. Recovery of macroinvertebrate density downstream was dependent on seasonal water discharge rates. Oyachen Creek, the downstream tributary, was dry for three of the sample dates negating the dilution effect reported in the previous study by Plotnikoff et al. (1988). Without this dilution, the downstream Blue Creek macroinvertebrate communities never recovered more than 39 percent from the initial density impact. There was a significant (0.05 level) difference in mean density for each downstream station when compared to upstream stations. The number of taxa was also reduced downstream of the mine drainage entry, but this was attributed to the overall density impact since diversity, similarity, and presence-absence showed only slight differences. There was a significant (0.05 level) difference in mean diversity in only one downstream station when compared to upstream stations. Comparison of the 1986 impact with1987 showed a similar level of initial impact. The amount of recovery differed and was attributed to the lower water discharge and subsequent extended drying of the downstream tributary in 1987. The Midnite Mine drainage with its increased conductivity, total hardness, sulfate, total solids, nitrate, and heavy metals have significantly reduced the macroinvertebrate densities of Blue Creek. Recovery from the drainage impact appears dependent on the overall water discharge level"--Document.