A screening-level evaluation of impacts to a Montana lotic macroinvertebrate community from a fuel oil spill

Abstract

A pipeline rupture during the winter of 1993 released an undetermined amount of refined fuel into a small stream on the. Flathead Indian Reservation in Montana, A screening-level bioassessment was performed in conjunction with supporting sediment and water analytical chemistry, to provide a preliminary evaluation of the. effects of the spill and subsequent remedial response actions on the benthic community. A variety of community-level metrics were compared to the habitat scores to evaluate the biological condition of each station sampled relative to the reference, thereby isolating effects related to contaminant release from those due to background habitat conditions. A comparison of taxa richness and Ephemeroptera:Plecoptera: Tricoptera (EPT) Index values from March 1993 to March 1994 indicated partial recovery at the rupture poing after intensive soil cleanup and remediation activities. Approximately one year following the spill, the rupture point exhibited 60 and 75 percent recovery respectively in taxa richness and EPT Index. At farther downstream stations, ≤15 and <10 percent recovery in taxa richness and EPT Index respectively were observed.