TRANSPLANTED OYSTER (CRASSOSTREA VIRGINICA) BEDS AS SELF-SUSTAINING MECHANISMS FOR WATER QUALITY IMPROVEMENT IN SMALL TIDAL CREEKS
Two reefs (2 m by 1.5 m) have been established in Hewletts Creek, New Hanover County, North Carolina. Water samples are collected monthly above and below each reef on ebbing tides. These samples are used to determine concentrations of total suspended solids (TSS), ammonium, and chlorophyll a. Flow properties are also measured above, over, and below each reef with an electromagnetic current meter. Additional samples and flow measurements are taken for comparison at adjacent control sites without restored reefs.
Initial data show TSS concentrations ranging from 24 mg l-1 to 41 mg l-1 above restored reefs to 23 mg l-1 to 39 mg l-1 below restored reefs near the tidal creek mouth. At the upland sites, concentrations range from 24 mg l-1 to 42 mg l-1 above and 15 to 39 mg l-1 below the restored reefs. Prior to reef placement, the percent organic content of TSS ranged from 25% to 55% at all sites. Since reef placement in early fall, percent organic content has decreased slightly both above and below the reef. These preliminary data suggest that after three months, the oyster reef has not yet altered the sediment load significantly in this system. As the restored reef continues to grow, however, we expect to observe a decrease in downstream (below reef) turbidity and nutrient load.