Use of oyster reefs as a tool in restoring tidal creek ecosystems

Increased coastal development is exerting previously unrealized pressure on shrinking natural resources.   Each year, coastal waters are subject to higher levels of runoff with increased nutrient and sediment loading. The net result is that coastal waters and local environs routinely suffer from habitat degradation, declining water quality, closure of waters to shellfishing, and quotas placed on many critical fisheries.  Unfortunately, many management practices employed to mitigate these impacts have proven ineffective or effective for only certain situations.  As part of an ongoing study conducted at the UNCW’s Center for Marine Science we have been evaluating the use of Crassostrea virginica, the Eastern Oyster, as a bioremediation tool in tidal creeks, which are primary fishery nursery habitats.  In this FRG proposal we propose to use oysters to reduce the load of inorganic and organic suspended particulates and selected nutrients. While this approach has been examined with mixed results in other systems, we have promising data that indicates even at relatively moderate density, small oyster reefs can significantly reduce total suspended solids, chl a, and ammonium in the surrounding water column.  A summary of the methods and results for this preliminary study can be found in the attached addendum. 

Our preliminary data suggest that scale may be a critical issue in reducing impacts from largely non-point source runoff.  Previous projects have targeted water quality changes in watersheds on a larger scale than is feasible given the dynamic nature of many of these tidal systems and available resources. We propose that constructing oyster reefs in the smaller bounded tributary creeks feeding these larger systems creates a greater encounter surface between oysters and the water they are filtering.  These tributary creeks are often the initial location of runoff inputs and also serve important primary nursery functions for many fishery species.  This situation enhances the oysters potential to improve water quality especially in areas with moderate impacts.  This type of habitat enhancement serves two purposes 1) provides an additional tool for managers to mitigate effects of development on our coastal systems, and 2) enhances critical habitats on a smaller scale that will be both cost effective and require less manpower than previous efforts, with a sufficiently manageable scale that it could be implemented by fishermen and citizens groups.

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