Bacterial utilization of total in situ dissolved carbohydrate in offshore waters1

Total dissolved carbohydrate declined steadily at rates of 1.5 and 2.6 µg C liter−1 h−1 during 12–24‐h dark in situ incubations in the Sargasso Sea and Gulf of Maine, indicating rapid bacterial metabolism. The source of this carbohydrate appears to be the extracellular release of phytoplankton photosynthate fixed during the most recent photoperiod. Observed rates require substantially greater primary production than indicated by the 14C method.