Biology and the Carbon Cycle
Oxygen Consumption, Denitrification and Carbon Oxidation Rates
in Near-Surface Sediments of the Arctic Ocean
John P. Christensen
As part of the multidisciplinary AOS-94 expedition, boxcores and piston
cores were collected at a variety of sites across the Arctic Basin. From these
cores, several pore-water solutes, including oxygen, nutrients, alkalinity, pH,
soluble iron and manganese, and sulfate, were measured. Sites ranged from
the continental slope off the Chukchi Sea to the abyssal plains and midbasin
ridges. Ten short cores were used for oxygen profiles, and seven longer cores
were used for the other dissolved solutes over the entire depth of the boxcore.
Profiles of pore-water-dissolved solutes help describe the biogeochemical
sequence of reactions occurring within the sediments. A slight lowering of the
oxygen concentrations was found within the upper few centimeters of pore
waters in all cores. In sites on the continental slope off the Chukchi Sea, pore-
water nitrate profiles show lowered nitrate concentrations at depth in the sedi-
ments. This reduction in nitrate concentrations is attributable to anaerobic
denitrification in the deeper strata of these sediments. These sediments also
received considerable inputs of biogenic material, as indicated by the elevated
levels of dissolved silicate in the pore waters. In contrast, most of the sedi-
ments throughout the central basins of the Arctic Ocean are oxygenated over
Kevin O'Toole, John
Christensen, and
Walt Olson standing
by for a box core on
the Polar Sea.
John Christensen is with the Bigelow Laboratory for Ocean Science in West Boothbay Harbor, Maine, U.S.A.
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