Responses of stream macroinvertebrate communities and water quality of five dairy farming streams following adoption of mitigation practices

Five streams in catchments with pastoral dairy farming as the dominant land use were monitored for periods up to 13 years after adoption of mitigation practices (MPs) to detect changes in stream macroinvertebrate communities and water quality. Water quality and macroinvertebrate community condition was degraded at the start with respect to N, P, suspended solids (SS), Escherichia coli concentrations, and a number of macroinvertebrate metrics, and were typical of catchments with intensive pastoral land use. Trend analysis showed a decrease in SS concentrations for all streams, generally increasing water clarity, and lower E. coli concentrations in two streams. The improvements, attributable to improved stream fencing and effluent disposal, were only sometimes associated with improved macroinvertebrate metrics, and suggest constraints of connectivity, habitat, time, and/or MP effectiveness. Macroinvertebrate species composition had the strongest correlation with total nitrogen at two sites, but changes probably reflected indirect factors associated with TN concentrations were responsible.