DEEP-SEA FLOOR RESPIRATION AS AN INDICATION OF LATERAL INPUT OF BIOGENIC DETRITUS FROM CONTINENTAL MARGINS

Sediment oxygen demand, estimated using in Situ chambers on a benthic lander, incubations of recovered cores and values previously published by others, has been used as a measurement of the flux of organic matter to the sea floor from the continental shelf and slope out to the abyssal plain in the northwest Atlantic. Rates were highest on the continental margin, and declined precipitously offshore. On the middle continental slope, rates were almost as high as those on the continental shelf, supporting the idea that mid-slope depths al ca 1000 m depth are a ''depocenter'' for particulate organic debris. The sediment oxygen demand, in terms of carbon equivalents (mg C m(-2) day(-1)), was generally lower than near-bottom POC fluxes measured in sediment traps. This imbalance is attributed to a combination of burial, anaerobic metabolism not reflected in oxygen demand, and continued lateral export along or offshore near the bottom. The exception to this pattern was the mid-slope depocenter, where the measured POC input was slightly less than the total organic carbon demand estimated with the lander. A comparison with other work suggests that at most depths on the continental margin the sediment oxygen demand is higher off the west coast of the U.S.A. than off the east coast. The upper to middle continental slope (500-1500 m depth) is the only zone over which sediment oxygen demand is higher on the east coast, but this can be attributed to the physiological limitations of low ambient oxygen concentration on heterotrophic metabolism in the pronounced oxygen minimum on the west coast.