Dissolved organic carbon associated with sinking particles can be crucial for estimates of vertical carbon flux

Sinking particles are a major vehicle of carbon export from surface waters of the ocean and thus their rates of sedimentation are important for assess ing the role of the ocean for the sequestration of atmospheric carbon dioxi de. Oceanographers often use sediment traps to estimate particle sedimentat ion. We suggest that the downward transport of carbon via particles may be underestimated, as dissolved organic carbon (DOC) released from trapped par ticles is not usually considered, thus hindering attempts to "balance" the carbon budget. Latent variable analyses of trap data enabled us to more acc urately estimate flux of particulate carbon. In particular, we present a me thod to separate the fraction of DOC leached from zooplanktonic swimmers fr om DOC originating from sedimented particles. The latter we term particle-a ssociated DOC (pDOC). The precise impact of this process in different ecosy stems may vary. Thus, an application of the statistical procedure should be made for individual sets of sediment-trap data at different locations. Our results from the central Greenland Sea from 1993 to 1995 indicate that the concentration of pDOC was from 25 % to several times the concentration of particulate carbon in individual sediment trap samples collected in three d epths. Thus, pDOC was a significant carbon pool for our investigation. We s uggest that the potential of pDOC as a "loss" factor in carbon budgets meri ts consideration in investigations aiming to accurately quantify the downwa rd transport of carbon in the ocean.