Southeast: South Atlantic Bight 

 Statement of Problem 



The SAB regional marine program was initiated 

 in 1975 in response to the need to understand more 

 about physical and biological oceanography processes 

 near shore, where potential impacts of floating nuclear 

 plants would be greatest. Although by the mid-seven- 

 ties, the possibility of such facilities had diminished, 

 new pressures were building for onshore domestic 

 energy development; these also could affect coastal 

 ecology. At that time, within the Savannah River 

 watershed alone, there were major nuclear fabrication 

 facilities of DOE's Savannah River Plant and three 

 operating and two planned nuclear power plants. Now, 

 there are 32 operating nuclear reactors in the 8 States 

 of the Southeastern Region. In addition, Savannah is a 

 major terminal for liquified natural gas and is 1 of the 

 top 10 U.S. shipping terminals for coal exports. The 

 region also has several home ports for nuclear sub- 

 marines; offshore, there are several planned leases for 

 oil and gas exploration. Before the consequences of 

 these diverse defense- and energy-related activities on 

 the marine environment can be assessed, a better un- 

 derstanding of the natural variability of circulation 

 patterns and biological systems is needed. 



Program Description 



The general objectives of the present South At- 

 lantic Bight program are to quantify the inputs and 

 production, transformations and fluxes of particulates 

 and associated energy-related byproducts within the 

 bight. (See figure 3 for a schematic diagram of the 

 SAB.) The ultimate end product of this research will 

 be to develop predictive mathematical models of the 

 dynamics of these particulates with special reference 

 to defining the routes, rates, and reservoirs for carbon, 

 nitrogen, associated energy-related organics, trace 

 elements, and radionuclides. 



The current SAB program is made up of 10 prin- 

 cipal investigators from 5 institutions all focusing on 

 determining the ultimate fate of materials injected into 

 the SAB system. The program's most recent studies 

 were the Spring Removal Experiment (SPREX) of 

 1985 and the Fall Removal Experiment (FLEX) of 

 1987: 



• SPREX: A study of cross-shelf transport of 

 materials during meteorologi- 

 cal/hydrographic regimes prevalent during 

 spring months. 



• FLEX: A study of cross-shelf transport of 

 materials during meteorological/ 

 hydrographic conditions prevalent during 

 the fall. 



Because the SAB program has been ongoing for 

 more than a dozen years, major syntheses publications 

 have been completed. Past studies have demonstrated 

 that major transport processes on the outer-middle 

 shelf are driven by fluctuations in the flow of the Gulf 

 Stream and wind events. On the inner shelf, transport 

 is controlled by wind events, tidal exchanges, and the 

 presence of low-density water from river runoff. 

 Transport usually is parallel to the shore line, except 

 when deflected offshore by shore line irregularities 

 (e.g., capes, bottom topography, or prevailing winds). 



When the Gulf Stream moves in an offshore 

 direction, significant amounts of upwelled water and 

 included materials intrude onto the continental shelf 

 about every 2 weeks. When the intruded waters remain 

 on the shelf for 3 days or more, large blooms of 

 phytoplankton and zooplankton populations occur. 

 The zooplankton which develop in this short time 

 period are dominated by gelatinous, asexually 

 reproducing forms. More advanced forms — e.g., 

 Crustacea — dominate with longer residence times. 

 These plant and animal populations rapidly scavenge 

 the nutrients and other elements from the water 

 column, converting them to particulate forms. The set- 

 tling particles enrich the sediments, primarily in the 

 capes and other areas of topographic irregularities. 

 During the summer, when shelf waters are thermally 

 stratified, the high levels of primary production in- 

 duced by these intrusions are not visible in surface 

 waters. Because this subsurface feature (probably 

 common to areas influenced by western boundary cur- 

 rents) was not recognized in the past, total primary 

 production-and hence the transport and fate of par- 

 ticles in such areas-has been greatly underestimated. 

 An accurate estimate of this dispersal of particles is 

 critical in the dispersal of energy-related by-products 

 in the region. 



Nearshore, a coastal frontal zone inhibits the 

 cross-shelf transport of material from the inner con- 

 tinental shelf. The inner front is characterized by water 

 with reduced salinity, large amounts of particulate 

 matter, and high biological production. Trace ele- 

 ments — and other material recycled between the 

 sediments and water column - and their net transport 

 out of the inner shelf are currently being studied. The 

 exchange of material between this inner and outer con- 

 tinental shelf is controlled by the effects of wind and 

 water density on frontal zone currents. 



Coastal Ocean Margins Program 



12 



December 1988 



