Ecosystem Services Provided by Oyster Reefs: An Experimental Assessment in Mobile Bay, Al (focus: infaunal community) - 2004-2006

The Alabama Oyster Reef Restoration Program began in 2004 to experimentally assess ecosystem benefits of oyster reef restoration in marsh creeks in Mobile Bay, AL, USA, and document the spatial scale at which such benefits could be measured. The project relied on a Before-After-Control-Impact (BACI) design in which 3 pairs of marsh creeks were monitored for 8 months prior to oyster additions, and fifteen months after oyster reef additions. Addition of oysters to one randomly selected creek of each of the three pairs resulted in densities higher than ever previously reported. We assessed whether oyster addition affected water clarity, nutrient dynamics, water-column primary production, benthic primary and secondary production, and abundance of juvenile fish and invertebrates by sampling monthly or bimonthly. While there were short-lived, small-scale increases in water clarity, there were no persistent, large changes in any response variables between experimental and control creeks. The absence of dramatic effects was likely due to a combination of factors, including inaccurate initial assumptions, between-creek variability and intense tropical storm activity. Regardless of cause, we did not find substantial changes in water clarity and biological activity in the experimental creeks. Therefore, we do not expect large ecosystem benefits to result from oyster restoration in other marsh creeks in the Gulf of Mexico. This is not to say that restoration of oyster reefs should not be carried out, especially since our oyster reef restoration was successful and functional oyster reefs offer other benefits such as enhanced benthic-pelagic coupling and denitrification through deposition of feces onto sediments. But our findings do suggest that surrounding landscape may play a critical role if the major goal of oyster reef restoration is to augment mobile fishes and decapod crustaceans.