Abstract:
Dredged materials from maintenance and deepening of inlets on coastal barriers are typically transported for disposal
in deep water or on land. An alternative is to treat dredged materials as a resource, placing them on the ebb-tidal
delta or subtidal shoals at depths where they are retained within the long-shore transport system and can nourish
eroding down-drift. beaches. Deposition of sediments onto subtidal shoals may, however, bury and selectively kill
populations of benthic invertebrates, or indirectly alter assemblages by modifying sediment characteristics. Core sampling
of the eastern (control) and western (disturbed) sides of Beaufort Inlet, North Carolina, twice before and once
8 months after a large (660,000 m') disposal revealed significant coarsening of sediments and associated changes to
assemblages of benthic macroinvertebrates in response to the perturbation. Impacts to sediments and macroinvertebrates
were closely correlated and, although greatest where sediment was directly deposited, extended over a wider
(at least 1km to the east) area than the deposition. Of the taxa comprising faunal assemblages, spionid polychaetes
were most affected by the disposal, declining in abundance. These results, which tie the deposition and dispersal of
coarse sediments on an ebb-tidal delta to changes in benthos, imply a biological cost that may be less than that of
direct nourishment of biologically productive intertidal beaches.
