Effects of adjacent land use on benthic macro-invertebrates in eastern Oregon

In the Pacific Northwest, agriculture has strong impacts on river systems, resulting in a degradation of riverine and riparian habitat quality. The Umatilla River drains a watershed dominated by agriculture in eastern Oregon, and alterations have been made in the river channel and on the adjacent land. In this study, macro-invertebrates were collected from three different riparian habitat types along the river: “test” sites that were heavily impacted by agriculture, “reference” sites that were relatively un-affected by agriculture, and “easement” sites that were designed to buffer the river from agricultural impacts. The communities were compared among these habitat types to determine the impacts of land use on the benthic aquatic assemblage. It was expected that test sites would be represented by a different abundance and diversity of macro-invertebrates than reference sites, and that easement sites would be similar to reference sites. Analysis of data showed that, as predicted, there are quantifiable differences between site types. Reference sites showed greater diversity and abundance for taxa sensitive to disturbance, and test sites showed greater abundance of taxa tolerant to disturbance. Easement sites were represented by macro-invertebrate communities that differed from both test and easement sites. This may be due to the effects of past land use and the relative age of the restoration project, and the taxonomic and habitat data collected will be further explored. Greater understanding of the effects of land management and restoration techniques on aquatic life, with long-term biomonitoring is necessary for the protection of freshwater systems.