Instream Ecosystem Processes and Stream Health: Assessing Ecosystem Services Provisioned by Native Freshwater Mussels in the Delaware and Susquehanna Rivers

Instream ecological processes regulate stream health at multiple spatial and temporal scales. The effectiveness of these key ecological services, however, may vary across a spectrum of ecological condition. Native freshwater mussels capture, remove and recycle sediment and nutrients from the water column through biofiltration and biodeposition activities. In addition to water purification, mussels also provision key bioavailable nutritional resources to the surrounding foodweb, supporting biodiversity. These ecosystem services are critical to freshwater ecosystems, including the Delaware and Susquehanna Rivers. Mussels are highly abundant and well-documented in the upper and middle Delaware River, where a collaborative, interdisciplinary study has been launched to 1) Evaluate biofiltration, nutrient flux and retention by mussels, 2) Quantify the economic value of freshwater mussel ecosystem services and 3) Develop a predictive model to estimate ecological and economic benefits and losses associated with predicted changes in the Delaware River basin related to factors including ecological flows and land use. Challenges may be associated with transferring this approach to other rivers and streams, as efficiency and effectiveness of instream ecosystem processes like mussel biofiltration vary with environmental conditions, as do costs and benefits associated with removal of particular nutrients and sediments. This challenge is relevant to the Susquehanna River, where nutrient loading is high, mussel abundance and juvenile recruitment are limited, and human-derived watershed stressors may confound or compromise the benefit of mussel-provisioned ecosystem services