Community Productivity with Sand Exposure in Urban and Forested Streams and effects of fine sediments on Grazers and Scrapers

Community metabolism can be measured using oxygen production and consumption. Oxygen is produced through photosynthesis, mostly during the day, and is consumed during respiration. High dissolved oxygen increases the capability of the stream to serve as an acceptable ecosystem to support aquatic life and allows diverse macroinvertebrates to settle. Our objective was to use oxygen production and consumption to determine the effects of sediment deposition on community metabolism in streams. Plastic trays filled with natural stream sediment were inserted in three urban and three forested streams for two weeks in riffles with canopy cover. Each week, sand was poured in the experimental trays. After two weeks, the trays were sealed for one hour using clear or darkened lids. Dissolved oxygen readings were taken in bright and dark trays to infer photosynthesis and respiration. Sand treatment significantly reduced productivity. Sand treatment did not affect metabolism. These results suggest that fine particle deposition in streams may reduce primary productivity.