Dissolved and particulate carbohydrates in contrasting marine sediments

Dissolved and particulate carbohydrates were examined in contrasting Chesap eake Bay (estuarine) and mid-Atlantic shelf/slope break (continental margin ) sediments. Particulate carbohydrates (PCHOs) represented similar to 5-9% of the total sediment particulate organic carbon (POC), and PCHO reminerali zation appeared to be a similar fraction of total sediment carbon oxidation (or C-ox). When these results are compared with results from other coastal sediments and a pelagic turbidite, PCHO remineralization (as a percentage of C-ox) did not vary by more than a factor of similar to 2-3 over a 3-4 or der of magnitude range in C-ox values. The causes of this are not well unde rstood, but may be related to specific effects associated with the reminera lization of highly altered organic matter mixtures under aerobic conditions . Dissolved carbohydrates (DCHOs) in these sediment pore waters ranged from similar to 30 to 400 mu M, increased with depth in a manner similar to tot al DOG, and represented similar to 10 to 55% of pore water DOC. In Chesapea ke Bay sediments this percentage decreased with sediment depth, while in th ese continental margin sediments it was constant (upper 30 cm). Of the DCHO s in these pore waters similar to 30 to 50% could be identified as individu al aldoses (monomeric neutral sugars), and total aldose yields (individual aldoses as a percentage of total DOG) were higher in these continental marg in sediment pore waters (>9%) than they were in the estuarine sediment pore waters (<5%). A comparison of DCHO and PCHO concentrations in these sedime nts indicates that their concentrations are uncoupled, and that pore water DCHO concentrations are primarily controlled by sediment remineralization p rocesses. Pore water DCHOs appeared to be preferentially found in the high molecular weight (HMW) DOC pool, and likely occur as some of the initial HM W intermediates produced and consumed during sediment POC remineralization. These results also support past suggestions about the differing controls o n carbon remineralization processes in continental margin versus estuarine sediments. Copyright (C) 2000 Elsevier Science Ltd.