Using macroinvertebrate communities to assess anthropogenic impacts in New York City’s surface water supply catchments

D.B. Arscott, J.K. Jackson, E.B. Kratzer, C.L. Dow, J.D. Newbold, A.K. Aufdenkampe, K.A. Kaplan, T.L. Bott, and B.W. Sweeney.Stroud Water Research Center

Macroinvertebrates were collected from 110 stream sites in New York City’s drinking water supply catchments during spring from 2000-2005. Fifty-three sites were in catchments where urban/suburban influences were prominent and 57 sites were in rural catchments with agricultural infrastructure or were primarily forested. A multimetric index derived from richness, organic pollution tolerance, and a model community index correlated strongly with urban/suburban descriptors (e.g., decreased richness with increasing urbanization) but suggested no biological impairment in agricultural catchments despite water quality concerns driven by elevated nutrient and ion concentrations. In contrast, multivariate analyses using species- and genus-level information revealed community changes along forested-to-agricultural gradients and these changes were related to nutrient and ion chemistry, among other factors. Biological assessments typically focus on quantification/detection of severely impacted sites and traditional metrics developed using that framework may not provide the sensitivity needed to assess differences among less disturbed sites, an activity important to drinking water providers and managers of protected areas. These analyses illustrate that subtle community changes can be related to land use and water chemistry signals providing managers with a greater potential of assessing water quality degradation via biological response.