Short time-series measurements of particulate organic carbon flux and sediment community oxygen consumption in the North Pacific

Abstract

Sediment community oxygen consumption (SCOC), a measure of organic carbon demand, and particulate organic carbon flux (POCF), a measure of organic carbon supply to the benthic boundary layer, were measured concurrently for short time intervals (2–14 days) over periods up to 49 days at two abyssal mud-bottom stations in the North Pacific. One station was located in the eutrophic eastern North Pacific off southern California (Sta. F, 4400 m depth) and the other in the oligotrophic central gyre (Sta. CNP, 5800 m depth). Measurements were conducted during two seasons: spring, which was previously characterized by higher and variable rates of SCOC and POCF, and autumn, which was characterized by lower, more consistent rates at both stations. SCOC was measured with a 4-chambered free vehicle grab respirometer, and POCF was determined from sinking particulate matter collected with sediment traps moored at 600 m above the bottom. There was no significant difference ( P > 0.05) between SCOC rates measured at the same station in the same season. Fluctuations in POCF were not reflected in SCOC at either station, and the intra-deployment variability in SCOC was as great as the interdeployment variability. Rates of SCOC were higher than POCF during both seasons at Sta. F but only in the spring at Sta. CNP. There was no appearance of synchronous or phased fluctuations in POCF and SCOC to suggest pelagic-benthic coupling on these time scales. Either long-term time-series measurements of SCOC and POCF or timedmeasurements to coincide with surface-water blooms are needed to identify coupling between passively sinking particulate organic carbon and the mineralization of organic matter by the deep-sea sediment community.