The function of created intertidal oyster reefs as habitat for fauna and marsh stabilization, and the potential use of geotextile in oyster reef construction

Two methods of oyster reef creation were tested: cultch additions to lower marsh fringe and use of geotubes "geotextile" as substrate for spat settlement and growth. Sediment stabilization and faunal utilization value of oyster cultch added to the lower intertidal marsh fringe of three created Spartina alterniflora marshes (two north - one south-facing) were examined. Significantly higher marsh edge vegetation loss was detected for non-cultched compared to cultched treatments at the south-facing site after a southeast storm. Significantly higher rates of sediment erosion were detected for the non-cultched treatments compared to cultched treatments at the south-facing site after the southeaster, and at the north-facing site after strong boat wake disturbance. Oyster development and reef fauna were measured for cultched and non-cultched treatments and nearby reference reefs. Within eight months we observed significantly higher abundances of the dominant species, Panopeus herbstii, Eurypanopeus depressus, and Alpheus heterochaelis within the cultched treatment compared to reference or non-cultched treatments. Crassostrea virginica spat settlement within the cultched treatment was equivalent to that of reference reefs. Tests with geotextile material indicate that it may provide substrate for spat settlement within four months, but at significantly lower abundances than shell substrate. Second year oyster settlement and growth on geotextile is currently being assessed. We conclude that addition of intertidal oyster cultch stabilizes marsh vegetation and sediment within created marshes and provides habitat for macrofauna. Also, the use of geotextile material for oyster reef construction may prove a suitable substrate and provide profile for constructed reefs. (DBO)