Geotube Oyster Substrate Research Project
Funding from the NOAA Restoration Center provided an opportunity to conduct a pilot study to gather scientific data on the efficacy of the use of geotextile materials as an alternative substrate for C. virginica reef construction at two sites, one subtidal, at the Cooperative Oxford Laboratory in the Tred Avon River, Maryland and the other intertidal, in the Newport River, North Carolina near NOAA's Beaufort North Carolina Laboratory. The lack of suitable substrate can be a limiting factor for marine organisms, including oysters. In the past, the primary use of geotextiles was to create barriers for reducing wetland and beach erosion and wave and current energies on transplanted vegetation and dredge sites. Traditional oyster restoration projects attempt to provide substrate for oyster colonization through the deployment of oyster shell, but this material is becoming depleted and alterative substrate types have and continue to be tested for suitability for reef construction. The use of concrete and marl rock have met with some success but are relatively expensive, while the use of concrete mixed with fly ash or coal ash, though less expensive, continue to be tested for leaching of toxic substances. Geotextiles may demonstrate multifaceted benefits (in addition to their use for erosion control structures and dredge material disposal for smaller sized projects) by providing a suitable hard substrate with vertical relief for C. virginica. To date research has indicated that C. virginica density for black polypropylene geotextile was initially lower than that observed for the control oyster shell treatments, but the persistence of the C. virginica and remnant shell left by deceased C. virginica on the geotextile material provided a nucleus for accelerated additional C. virginica set, and within a few years provided a substrate that could support oyster densities similar to that of oyster shell controls.