Longitudinal Changes in Stream Macroinvertebrate Communities Along a Gradient of Stormwater Inputs

Elaine Langone Center, Terrace Room

This study examined changes in water quality along a gradient of stormwater systems using the macro-invertebrate communities. The diversity and species of macro-invertebrates will change as stormwater inputs increase. We hypothesized that the macroinvertebrate community will change to one dominated by tolerant taxa like chironomids and oligochaete worms as more stormwater drains into the stream. To test this hypothesis, macroinvertebrates were collected from ten different sites along Millers Run (Williamsport, PA). Water chemistry and habitat data were also collected at the same ten sites. Insects were identified down to family. Calculations of macroinvertebrate community composition and diversity were used to assess the effects of stormwater inputs. A higher number of pollution sensitive taxa were found in sections with low stormwater inputs than sections with high inputs. Oligocheates and chironomids were found towards the mouth of the stream after passing several stormwater inputs. Water chemistry also showed higher levels of phosphorus and nitrogen at the mouth of the stream indicating higher pollutants in the water. Riparian cover was lowest in the areas where the stream flowed through Williamsport. The data supported our hypothesis that stream quality decreases as it passes along a gradient of stormwater inputs. This demonstrates the importance of stormwater inputs and not just urban development as a cause of poor water quality in streams.