of organic matter from sources (estuaries, blooms, sediments) that may be advected into or 

 exported from the Hatteras region. One or more cruises may incorporate detailed consideration 

 of the cold pool, a band of cold bottom water on the outer shelf where patterns of carbon 

 catabolism can be followed on a large scale over several months. This is a potentially unique 

 natural experiment that nicely complements short-term process experiments being performed at 

 Hatteras. 



E. Vertical Transport (Sinking and Resuspension) 



Among the least studied aspects of the carbon cycle are the in situ sinking rate of 

 naturally occurring particles, the rates of release of dissolved organic matter from sinking 

 particles, and the role of benthic resuspension in determining the character and quantity of 

 carbon transported off the shelf. 



Sinking rates determine whether particles generated in the neritic zone are deposited in 

 the sediments of the continental margin. Rapidly sinking particles are retained on the shelf, 

 whereas slower sinking particles are transported seaward. The particle spectrum will be sorted 

 and differentially deposited as a function of the sinking speeds of the individual particles and 

 the flow field of the water. Thus, fluxes and sinking speeds of particles, coupled with the flow 

 field determine where deposition occurs on the continental margins. 



Water entering the ocean's interior at Cape Hatteras has traveled over an extensive 

 shallow continental shelf. In this region, the benthic boundary layer is frequently within the 

 euphotic zone and often occupies a significant fraction of the total water column. Storm- 

 driven resuspension of particles and pore water from the sediment is common. Thus, 

 dissolved and particulate material in water exiting the shelf may be newly produced, or may 

 have experienced biogeochemical transformation under both aerobic and anaerobic conditions, 

 and by benthic as well as pelagic organisms. Unlike recently produced organic matter, this 

 reworked material is unlikely to be oxidized in the ocean interior. The relative proportion of 

 refractory DOC and POC leaving the shelf depends on processes occurring in the benthic 

 boundary layer and on fluxes occurring at the sediment/water interface on inner and mid-shelf 

 regions. 



F. Burial 



Burial in continental margin sediments is the dominant mechanism by which organic 

 carbon is removed from the oceans. In the MAB, extremely high rates of organic carbon 

 burial have been reported in the Chesapeake Bay estuary and in the continental slope 

 depocenter at approximately 500- 1000m water depth. Unlike open ocean systems where only 

 a very small fraction of the deposited organic matter survive sediment diagenesis to be buried, 

 margin systems may bury a significant (>50%) portion of the deposited materials. 



Burial rates require knowledge of sediment accumulation rate and of the accumulation 

 history of each location. The use of natural radionuclide and anthropogenically-derived tracers 

 wiU play a key role in constraining deposition. Biomarker tracers, that may provide insight 

 into the origin of the accumulating organic matter, will be used in conjunction with burial 

 estimates to assess recent changes in burial patterns in the continental margin system. 



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