A bioassessment of the impact of livestock restriction on benthic macroinvertebrate communities in the Grand River watershed in Ontario, Canada

摘要

Livestock exclusion from streams is a best management practice applied in attempts to improve water quality in the Grand River watershed in Ontario, Canada. Because of the lack of resources, minimal biomonitoring is conducted to assess the impacts of the fencing on water quality. The purpose of this study was to fill in the gaps by 1) determining if fence length and age of fence influenced the water quality within fenced areas, and 2) compare current water quality conditions of fenced locations to historical data. Benthic macroinvertebrates were used as an indicator of water quality, and a suite of biological indices (taxa richness, abundance of Ephemeroptera, Plecoptera, Trichoptera, Oligochaeta and Chironomidae, Shannon Wiener Index, Simpson’s Index, and Hilsenhoff’s Family Biotic Index) were used to compare upstream, midstream, and downstream locations of fences with varying ages and lengths, using ANCOVA and Kruksal-Wallist tests. Invertebrate samples collected in 2014 were compared to invertebrate samples collected in 2007 using paired t-tests. There were minimal statistical significances when comparing invertebrate samples between fenced areas of different ages and lengths, and minimal differences between the 2007 and 2014 data. The lack of significant differences suggests that livestock exclusion may not be facilitating passive restoration. However, upstream pollutant inputs may be masking the impacts livestock exclusion has on water quality, as a result of cumulative effects. Other best management practices and strategies may need to be implemented in order to have measureable improvements to water quality.