Organic-carbon levels typically are low (<0.2%) in shelf sands off Sapelo Island, Georgia. However, a distinct lobate belt of relatively “carbon-rich” sand (>0.3% organic carbon), concave landward, is located at sound entrances around the seaward periphery of ebb-tidal shoal complexes. This distribution pattern indicates that organic detritus, derived mainly from salt marshes, is exported from the sounds and is deposited just offshore because of waning hydraulic tidal currents combined with negligible wave activity. Organic carbon transported from the sounds to the inner shelf evidently helps support a thriving macrobenthic community consisting dominantly of polychaetes, mollusks, and crustaceans.

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