The importance of tidal creek ecosystems

Tidal creeks are widespread and abundant estuarine ecosystems, yet their ecological relevance is undervalued as reflected by the lack of research on these systems relative to larger, better-known estuarine systems (e.g. the Chesapeake Bay, the Albemarle–Pamlico Sound System, Florida Bay, to name a few). These better-known large estuaries contain numerous tidal creeks which, in comparison to the estuary proper, have distinctly diverse hydrological and watershed characteristics that can heavily influence ecosystem function and impact human use of these resources (Sanger et al., 1999a; Lerberg et al., 2000; Mallin et al., 2000). Because tidal creek ecosystems generally have a higher surface-to-volume ratio than larger, river-dominated estuaries, and because they are so abundant and widespread, their collective importance in material transfer and other ecological processes may equal or exceed that of larger estuaries in certain geographic regions (Dame et al., 2000). Tidal creeks are especially abundant in low-energy systems such as protected areas behind barrier islands along the Atlantic Intracoastal Waterway (ICW), or tributaries to large estuaries or rivers. They are most abundant along the Atlantic Seaboard from New Jersey to Florida, and along the Gulf Coast. As an example, the four southernmost coastal counties in North Carolina (Onslow, Pender, New Hanover and Brunswick) contain at least 73 tidal creeks that are second-order or larger. Each of these creeks receive drainage from first-order and intermittent tributaries, and many more of the latter systems discharge directly into large estuaries and rivers. Tidal creeks are present, but less abundant, in highenergy systems such as the rocky intertidal of the northeast United States and eastern Canada, the open beaches of the California coast and the steep coastlines of the US and Canadian Pacific Northwest. Tidal creeks generally range in size from first-order to fourth-order streams, and from < 1 to > 10 km in length. Their depth rarely exceeds 3.0 m at high tide, and some tidal creeks contain broad intertidal sand or mud flats. Tidal creeks can be categorized as follows. High-salinity (polyhaline to marine) tidal creeks are found along the sound side of barrier islands and in Coastal Plain salt marsh estuaries such as South Carolina’s North Inlet (Dame et al., 1991). These creeks have strong tidal influence and are characterized by marsh vegetation throughout. A second major category consists of mesohaline to polyhaline tidal creeks draining continental uplands. These creeks drain into larger