North and South Carolina Coasts

Abstract This coastal region of North and South Carolina is a gently sloping plain, containing large riverine estuaries, sounds, lagoons, and salt marshes. The most striking feature is the large, enclosed sound known as the Albemarle–Pamlico Estuarine System, covering approximately 7530 km2. The coast also has numerous tidal creek estuaries ranging from 1 to 10 km in length. This coast has a rapidly growing population and greatly increasing point and non-point sources of pollution. Agriculture is important to the region, swine rearing notably increasing fourfold during the 1990s. Estuarine phytoplankton communities in North Carolina are well studied; the most important taxonomic groups are diatoms, dinoflagellates, cryptomonads and cyanobacteria. Several major poorly flushed estuaries are eutrophic due to nutrient inputs, and toxic dinoflagellates (Pfiesteria spp) can reach high densities in nutrient-enriched areas. Fully marine waters are relatively oligotrophic. Southern species enter in subsurface intrusions, eddies, and occasional Gulf Stream rings, while cool water species enter with the flow of the Labrador Current to the Cape Hatteras region. The Carolinas have a low number of endemic macroalgae, but species diversity can be high in this transitional area, which represents the southernmost extension for some cold-adapted species and the northernmost extension of warm-adapted species. In North Carolina the dominant seagrass, Zostera marina, lies at its southernmost extension, while a second species, Halodule wrightii is at its northernmost extent. Widgeon-grass Ruppia maritima is common, growing in brackish water or low-salinity pools in salt marshes. Seagrass meadows are now much reduced, probably due to elevated nitrogen and increased sedimentation. In sounds, numerically dominant benthic taxa include bivalves, polychaetes and amphipods, many showing gradients in community type from mesohaline areas of the eastern shore to near marine salinities in western parts. The semi-enclosed sounds have extensive shellfisheries, especially of blue crab, northern quahogs, eastern oysters, and shrimp. Problems include contamination of some sediments with toxic substances, especially of metals and PCBs at sufficiently high levels to depress growth of some benthic macroinvertebrates. Numerous fish kills have been caused by toxic Pfiesteria outbreaks, and fish kills and habitat loss have been caused by episodic hypoxia and anoxia in rivers and estuaries. Oyster beds currently are in decline because of overharvesting, high siltation and suspended particulate loads, disease, hypoxia, and coastal development. Fisheries monitoring which began in the late 1970s shows greatest recorded landings in 1978–1982; since then, harvests have declined by about a half. Some management plans have been developed toward improving water quality and fisheries sustainability. Major challenges include; high coliform levels leading to closures of shellfish beds, a problem that has increased with urban development and increasing cover of watershed by impervious surfaces; high by-catch and heavy trawling activity; overfishing which has led to serious declines in many wild fish stocks; and eutrophication. Comprehensive plans limiting nutrient inputs are needed for all coastal rivers and estuaries, not only those that already exhibit problems. There is a critical need to improve management of non-point nutrient runoff through increased use of streamside vegetated buffers, preservation of remaining natural wetlands and construction of artificial wetlands. Improved treatment processes, based on strong incentive programmes, should also be mandated for present and future industrial-scale animal operations.