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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Landscapes
Factors affecting the distribution of macroinvertebrates in the New York City drinking water watersheds
E.B. Kratzer, J.K. Jackson, D.B. Arscott, A.K. Aufdenkampe, C.L. Dow, L.A. Kaplan, and B.W. Sweeney. Stroud Water Research Center, Avondale, PA USA 19311
Macroinvertebrates were collected over 3 consecutive years at 60 sites spread across watersheds that are the source of drinking water for New York City. We applied direct gradient techniques to the macroinvertebrate data and numerous land cover and water chemistry variables to explore spatial variation patterns among macroinvertebrates. Environmental variables and macroinvertebrate taxa separated sites east of the Hudson River from sites west of the Hudson, suggesting gross biogeographical differences between the 2 regions. Both land use and water chemistry explained 74 and 82 % of variation in macroinvertebrates in the eastern and western regions, respectively. Macroinvertebrates were distributed along 2 impact gradients in the eastern region: forested-to-urban and forested-to-point sources. Community structure measures (e.g., total and EPT richness and Percent Model Affinity) were correlated with the forested-to-urban gradient. In the western region, macroinvertebrates were distributed along a forested-to-agriculture gradient and a pH gradient. However, impact gradients in the western region are less severe, and community structure measures such as richness did not decline at the impacted ends of the gradients. These results suggest that macroinvertebrate differences along these gradients may reflect species replacements, not losses.
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