Dissolved organic carbon in the upper ocean of the central equatorial Pacific Ocean, 1992: Daily and finescale vertical variations

Detailed depth profiles of dissolved organic carbon (DOC) were determined at the JGOFS Equatorial Pacific Time Series site at 0°, 140°W in March/April and October 1992. DOC concentrations in the top 200 m, determined with the high temperature combustion (HTC) method, showed no elevated values over previous wet chemical estimates and ranged from an average of 67 μM C in the surface waters to 46 μM C at 200 m. The average integrated DOC concentration over 200 m was 11.4 mol C m−2 in March/April and 11.0 mol C m−2 in October. Variability frequency (i.e. seasonal) was minimal despite large changes in many biogeochemical parameters. Vertical distribution of DOC was highly correlated with physical properties and remained relatively independent of biological properties. High frequency variability appeared to be governed by physical processes. DOC production and consumption in the equatorial Pacific were tightly coupled, resulting in little accumulation and export of labile DOC.