Nature and Transformations of Particulate Carbohydrates in the Oceanic Water Column

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Carbohydrates represent a major organic component of all marine organisms, especially phytoplankton, and thus these substances constitute a large fraction of oceanic particulate organic matter (POM). However, in comparison to other important groups of biomolecules, eg, lipids and proteins, surprisingly little attention has been paid to carbohydrates in oceanic POM. Therefore, a study to test the following hypotheses: 1. During descent of particles in the water column, storage carbohydrates are preferentially lost while structural polysaccharides are relatively enhanced in the residue. The latter compounds can be used as biomarkers, while loss of the former may be used to estimate the energy potential (caloric value) and rate of degradation of POM with depth; 2. Algae are the major sources of carbohydrates in the sea, but close to land, terrigenous sources may become locally important. These inputs can be differentiated on the basis of their carbohydrate compositions; 3. As a result of microbial degradation during descent of particles, new polysaccharides are formed. These new saccharides are to a large degree compositionally distinct from the original materials and thus may be used to estimate the degree of microbial degradation POM. The study will be based largely on analyses of samples from sediment traps deployed as part of the VERTEX Program. Analytical techniques will include the use of selective depolymerizations coupled with high resolution GC and HPLC. When put in the context of the VERTEX Program, especially work being done on proteins, lipids, and microbial activity, the proposed study of carbohydrates should contribute significantly towards our understanding of the processes affecting fluxes of organic material and diagenesis in the watr column.