Preliminary Study of the Effects of the Arrastra Creek Effluent on Benthic Macroinvertebrates of the Big Blackfoot River

Abstract

I sampled benthic macroinvertebrates from three replicate sites above and three sites below the confluence of Arrastra Creek and the Big Blackfoot River. A total of 15 families were collected and identified from the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT). A t-test determined that the diversity and abundance of macroinvertebrates was significantly lower below the confluence of Arrastra Creek and the Blackfoot River than above. The cause of the decrease in macroinvertebrate populations and family richness may be due to increased sediment coming from the Arrastra Creek effluent. My personal observations suggest that the increased sediment may be due to cattle destroying the riparian zone. The destruction of the riparian zone may lead to increased erosion and therefore increased sediment into Arrastra Creek.