Mineralization of dissolved organic carbon in the Sargasso Sea

The lability of dissolved organic carbon was estimated in the Sargasso Sea. Rates of DOC mineralization were estimated by monitoring, with high precision, the accumulation of CO2 in dark incubation bottles after the removal of particles > 0.8 μm in size. The minimum incubation time used in these experiments was 24 h. Rates from three 24 h incubations conducted on water from 20 m fell in the narrow range of 0.44–0.45 μM C d−1. These rates ranged from approximate equivalence to more than 100% greater than the concurrent rates of primary productivity, suggesting in some cases that gross primary productivity was underestimated or that there existed labile DOC produced earlier in time, thus supporting periods of net heterotrophy in the Sargasso Sea.