Stream restoration effects on detritus matter and macroinvertebrates

In general, invertebrates in freshwater systems are important mediators of the fragmentation of organic matter, thus influencing nutrient cycling and energy flow within stream food webs. In the last decade, those stream systems in Lancaster County significantly impacted by changes in land-use have been frequently restored in terms of channel design to alleviate suspended sediment and nutrient loading issues that impact downstream systems. This study was initiated to evaluate restoration effects on the macroinvertebrate community structure involved with processing organic matter (leaf packs). Leaf packs of dried tulip and oak leaves (4 gm/pack) were placed in riffle sections (n=6 packs/date) of the restored reach and a control stream, and were collected over a three-week period before restoration and 30 months after restoration. Packs were dried and weighed to determine rate of decomposition over time. Macroinvertebrates were identified to family level to determine diversity and abundance. Preliminary results indicate that tulip leaves decomposed at a faster rate both pre and post restoration compared to oak leaf packs, but rates did not differ between pre and post restoration. Macroinvertebrate diversity and abundance did not differ within sample years or between pre and post restoration. Often, post restoration monitoring of stream restoration projects does not continue much past restoration, and examinining how they influence organic matter processing is completely ignored. This preliminary study provides much needed baseline data to assess how restoration may influence organic matter decomposition rates and potentially nutrient cycling and retention in a consumer-based system.