Impact of fine sediment pollution due to grazing on aquatic macroinvertebrate diversity in Utah streams

The composition of aquatic macroinvertebrate communities is often used as an indicator for overall stream health due to their response to changes in stream conditions. A stream microhabitat with a high diversity and abundance of macroinvertebrates is riffles. Riffles are shallow areas of the stream with high oxygen content, hence why they are a favored condition for many macroinvertebrates. Alterations to the composition of riffles can therefore have a large impact on the macroinvertebrate community. An example of this is how changes in embeddedness of substrate in fine sediment may reduce the habitat for certain taxa of macroinvertebrates, making the riffle unsuitable for them. Activities like free-range cattle grazing can contribute to fine sediment pollution in a stream. This project compares two mountain streams in Utah county; one with historic and current free-range cattle grazing and one without. We are comparing substrate size, embeddedness, and macroinvertebrate community composition in riffles. In this study, we will assess whether grazing is influencing riffle embeddedness and macroinvertebrate diversity, and which macroinvertebrate taxa may be sensitive to grazing pressures.