Reconciling particulate organic carbon flux and sediment community oxygen consumption in the deep North Pacific

Abstract

THE mineralization of organic carbon in the deep ocean has been considered an enigma in the North Pacific. Comparisons of the supply of particulate organic carbon (POC) with estimates of its mineralization to CO2 by the sediment community have indicated that the supply of POC sinking into the benthic boundary layer may be as much as 97% short of meeting the organic carbon demand of the sediment community1,2. These previous findings were based on short-time-series measurements (<14 days) conducted in situ with sediment traps and benthic respirometers. We report here a comparison of long-time-series measurements (2.3 years) of POC flux into the benthic boundary layer and concurrent, seasonal measurements of sediment community oxygen consump-tion. We chose a single abyssal station (4,100 m depth) in a region of the eastern North Pacific where there is a strong seasonal fluctuation in primary production, and where previous studies1,2 showed the supply of POC to be as much as an order of magnitude lower than the demand by the sediment community. Our measure-ments, using the same methods, show agreement to within 15% between organic carbon supply and demand. This reconciliation is attributable to the inclusion of previously undetected episodic inputs of POC into the benthic boundary layer. These episodic inputs are critical to sustaining the sediment community at this station, and are probably important in other deep-sea environments where seasonal fluctuations in primary production are prominent in surface waters.