STABILIZATION AND EROSION CONTROL VALUE OF OYSTER CULTCH FOR INTERTIDAL MARSH

Oyster cultch was added to the lower intertidal fringe of three create d Spartina alterniflora marshes to examine its value in protecting the marsh from erosion. Twelve 5-m-wide plots were established at each si te, with six randomly selected plots unaltered (noncultched) and cultc h added to the remaining (cultched) plots. Within each cultched plot, cultch was placed along the low tide fringe of the marsh during July 1 992, in a band 1.5 m wide by 0.25 m deep. Marsh-edge vegetation stabil ity and sediment erosion were measured for each plot from September 19 92 to April 1994. Significant differences (p < 0.05) in marsh-edge veg etation change were detected at the only south-facing site after a maj or southwester storm. Significantly different rates of sediment erosio n and accretion also were observed at this same site. Areas upland of the marsh edge in the cultched areas showed an average accretion of 6. 3 cm, while noncultched treatment areas showed an average loss of 3.2 cm. A second site, with northern orientation, also experienced differe ntial sediment accretion and erosion between treatment type, caused in stead by boat wakes that were magnified by the abutment of a dredge ef fluent pipe across the entire front fringe of the site. During this pe riod we observed significant differences in sediment accumulation, wit h the areas upland of the marsh edge in the cultched treatment having an average accretion of 2.9 cm and the noncultched an average loss of 1.3 cm.