Wednesday, June 6, 2007 - 10:15 AM
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Periphyton response to simulated nonpoint source pollution in the lower Muskegon River watershed, Michigan

Peter J. Hrodey, Kelly J. Wessell, Mary E. Ogdahl, Scott T. Kendall, and Alan D. Steinman. Annis Water Resources Institute, Grand Valley State University, 740 W. Shoreline Dr., Muskegon, MI 49441

The lower Muskegon River empties into an extensive wetland before flowing into Muskegon Lake.  This complex system receives runoff (i.e., nonpoint source (NPS) pollution) from multiple land uses, including agriculture, residential, and urban sources, which could affect the system’s ecological integrity. The objective of this study is to understand how NPS effects are integrated across multiple trophic levels in three habitats (river, wetland, lake) and among seasons.  Here, we report periphyton response to simulated NPS-contributing events in the lower Muskegon River watershed. Following nutrient and salt additions (5-10x ambient), we measured a suite of variables at each habitat including periphyton biomass (AFDM), chlorophyll a, and community metabolism.  In the wetland, there were no significant differences observed for any variable during any season as a result of nutrient enrichment.  In the lake, mean AFDM and chlorophyll a were significantly higher on substrates in nutrient treatments (59 g m-2, 21 µg cm-2) than controls (39 g m-2, 6.5 µg cm-2) during summer.  In the river, road salt significantly increased gross community production and community respiration during winter and spring.  These preliminary results suggest that periphyton response to NPS pollution is variable and may be dependent upon habitat, seasonal dynamics, and stressor.