weight compounds that are likely to be biologically labile and high molecular weight 

 compounds that may be biologically labile, but may also be nearly completely refractory or 

 labile to only a few oxidative processes. In the latter case, oxidation may be incomplete, and 

 may occur under unique environmental conditions or require the participation of specific 

 groups of organisms. 



Several processes are likely to produce pulses of DOC in continental shelf waters. 

 Phytoplankton are likely to make significant contributions to DOC pools when nutrient limited 

 at the end of blooms, or when experiencing other kinds of environmental stress. New 

 techniques being developed as part of the OMP program will permit rapid evaluation of the 

 metabolic state of bloom-forming phytoplankton in the water column and will greatly facilitate 

 identification of water masses in which release of photosynthate by phytoplankton is a 

 potentially important source of DOC. 



Much of the DOC released by phytoplankton will be biologically labile. Thus, it is 

 important to evaluate rates of bacterial transformation of recently produced DOC to POM, 

 CO2, and refractory organic compounds. These rates will depend on the species of 

 phytoplankton associated with the blooms, and the taxonomic identity of bacteria in the water 

 column. OMP research in molecular ecology is designed to provide species- specific 

 determinations of bacterial growth rates, and species-specific determinations of phytoplankton 

 physiological state. Additional pulses of DOC may originate with the bacterial pool of POM 

 when epidemics of viral infection occur. 



Zooplankton feeding may also produce pulses of DOC, either directly through inefficient 

 grazing, direct excretion, or by production of fecal material from which DOC is leached. A 

 major gap in our ability to budget the transformation of carbon by zooplankton is the lack of a 

 technique for the determination of DOC production by zooplankton. Several approaches to 

 this problem are in developmental stages for use during the major field season. 



Storms are episodic events that are responsible for pulses of DOC input to the water 

 column from sediment pore waters. Benthic resuspension associated during storms is also a 

 mechanism for moving particles that will leach DOC into the water column. Because of the 

 large expanse of shallow continental shelf that acts as a "drainage" for export from the OMP 

 at Cape Hatteras, there is a large reservoir of geochemically old, highly refractile DOC in the 

 pore water of the sediments on the shelf. The flux of this material from the continental shelf 

 to a permanent sink in the ocean's interior will be determined by the lability of the DOC 

 introduced to the water column by benthic resuspension, and the frequency of resuspension 

 events. 



G. Transformations of Detrital POC 



The fate of carbon in the shelf and slope system will depend on the extent of 

 remineralization, removal by lateral exports, and burial in underlying sediments after biological 

 incorporation. Most of the photic zone production is recycled within the water column. 

 Besides considering grazing as a sink for phytoplankton carbon, it is worth considering it as a 

 source of degradation for materials sinking from the photic zone, particularly as aggregates or 

 snow particles. Zooplankton can utilize detrital "snow" particles as food in at least two ways: 

 by ingestion of entire particles, including attached bacteria, phytoplankton, micro- and meso- 

 zooplankton; or by selective ingestion of specific components of the particles. Methods to 



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