Estuarine–Coastal Interactions
The coastal ocean is a dynamic region where the rivers, estuaries, ocean, land, and the atmosphere interact (Walsh, 1988; Mantoura et al., 1991; Alongi, 1998; Wollast, 1998). Coastlines extend over an estimated 350,000 km worldwide, and the coastal ocean, typically defined as a region that extends from the high water mark to the shelf break (figure 16.1; Alongi, 1998), covers approximately 7% (26 × 106 km2) of the surface global ocean (Gattuso et al., 1998). Although relatively small in area, this highly productive region (30% of the total net oceanic productivity) supports as much as 90% of the global fish catch (Holligan, 1992). In recent years, the coastal ocean has been recognized for its global importance with both national and international programs such as the Land–Ocean Interactions in the Coastal Zone (LOICZ) program, a subprogram of the International Global Change Program (IGBP) started in 1993 (Pernetta and Milliman, 1995), the European Union coastal core project (European Land–Ocean Interaction Studies, ELOISE) (Cadée et al., 1994), and in the U.S. Shelf Edge Exchange Processes Program (SEEP I and SEEP II) (Walsh et al., 1988; Anderson et al., 1994), the Coastal Ocean Processes (CoOP) program, Ocean Margins Program (OMP), and Land–Margin Ecosystem Research (LMER), to name a few. SEEP I and SEEP II were designed to test the Walsh et al. (1985) hypothesis that increased anthropogenic nutrient supply to the coastal ocean would result in enhanced burial of organic matter in continental margins due to higher offshore export of new productivity in the nearshore waters. While the hypothesis of offshore transport and burial was shown to be valid along certain regions of the eastern U.S. coast, other regions showed a more along-shelf transport (Walsh, 1994). More recent work in the OMP, which revisited some of the objectives of SEEP I and SEEP II, found that the accumulation of organic matter in upper slope sediments was only <1% of the total primary production in the entire continental margin of North Carolina (DeMaster et al., 2002). There are many factors that will ultimately determine if and how much nearshore production is exported offshore from the coastal ocean.