INDICATOR INVERTEBRATES: DETERMINING CHANGE IN BENTHIC MACROINVERTEBRATE COMMUNITIES DUE TO DEPOSITED SEDIMENT IN THE NORTHERN GREAT PLAINS

Abstract

Excessive sedimentation is a major stressor to ecosystem health in freshwater systems globally. Benthic macroinvertebrates are excellent bioindicators of ecosystem health because they have a range of environmental tolerances and are typically associated with certain substrate types. This study tested the hypothesis that sedimentation is a driver of benthic macroinvertebrate communities by determining their responses to increased deposited sediment levels in the Northern Great Plains using both experimental and survey approaches. In both approaches, the effects of deposited sediment were isolated, the responses of specific indicator invertebrates were characterized and finally, indices that commonly respond to deposited sediment were analyzed for their sensitivity. At the community level, the overall multivariate redundancy model was not significant and deposited sediment accounted for only 0.2% of the total variation in species composition in the river survey. Indicator species analysis identified taxa that were associated with sediment impairment classes in both studies. Index sensitivities indicated that Percent Swimmers responded to sediment and can potentially be used as an index of deposited sediment in this region, however this index was not sensitive to sediment in the landscape-scale survey. Although individual taxa that responded to sediment deposition may be used as bioindicators of sediment impairment in further studies, the relatively small effect of sediment at the community level and on univariate composition metrics suggests benthic macroinvertebrate communities are adapted to deposited sediment in the Northern Great Plains.