Restoration Research Projects

Geotube material was tested to determine if it could be used as suitable substrate for oyster spat.

Oyster populations appear to be declining in many east coast areas and attempts to restore viable populations has become a major concern (Lenihan et.al. In press) The NOAA RC provided funding to investigate the potential use of geotextile material for oyster reef (Crassostrea virginica) creation. The US Army Corps of Engineers has been employing geotextile material filled with sediment for use as groins and wave-energy dispersant. The structures, i.e. geopillows and geotubes, comprise a firm substrate that may provide benefits beyond those originally intended.

While oyster restoration projects attempt to provide substrate for oyster colonization through the deployment of oyster shell, the shell is becoming depleted and alternative substrates types have and continue to be tested for reef construction. The use of geotextile potentially has multifaceted benefits through the production of erosion control structures, dredge material disposal for smaller sized projects, and the production of a hard substrate with vertical relief which might provide habitat for C. virginica. One panel treatment included oyster shells affixed to geotextile material on a PVC frame. Two other panel treatments involved black and white geotextile panels affixed to PVC frames. All three treatments were tested under shaded and unshaded conditions yielding a total of six treatments (Meyer 1997).

The data resulting from this study indicated that while oyster spat settlement was significantly lower on geotextile treatments than on shell treatments, there were C. virginica accumulations on the material. Black geotextile material appeared to be a more preferable substrate for settlement than white geotextile. Shaded treatments also had better settlement than unshaded treatments. Implications for restoration based on these results are that sediment filled geotextile could be a useful material for oyster settlement and that addition of some shell treatments would increase settlement rate. Shading also apparently enhances spat settlement rates on substrate. These geotubes could be used as the foundation for spawner-recruit sanctuaries or other areas where oyster harvest would be limited. A manuscript from this work is currently underway. Sample processing and data analyses are continuing.