The Role of Biomass, Bioturbation and Remineralization in Determining the Fate of Carbon in the Arctic Ocean

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The goal of biological studies during AOS-94 was to understand the role

of the Arctic in the global carbon cycle. In support of this goal, our research

examined the fate of organic matter reaching the seafloor. Little work had

been done on benthic (seafloor) carbon in the Amerasia Basin prior to this

cruise, but based on work from the Eurasia Basin we surmised that a greater

portion of carbon fixed by pelagic (water column) phytoplankton would reach

the bottom in the entire Arctic Ocean than in other oceans. Possible explanations

for a greater pelagic/benthic coupling included low zooplankton abundance and

feeding rates and a temperature-supressed microbial loop. One of the major

strengths of this cruise was that other researchers were addressing pelagic phyto-

plankton, zooplankton and microbial processes simultaneously throughout the

cruise.

Our main hypothesis was that the relatively abundant and active benthic

community found in the Arctic is the major factor controlling (both directly

and indirectly) the fate of sedimentary carbon in polar regions. We focused on

some of the possible fates of carbon reaching the benthos by examining patterns

of benthic biomass (how many animals there were), particle bioturbation (how

deep the animals were mixing particles in the sediment) and a variety of esti-

mates of benthic food availabilty (how much total carbon, organic carbon,

chlorophyll, phaeopigments and biologically available protein). In addition

we determined a suite of rate measurements, including remineralization (how

much oxygen is being used by the animals) and bioirrigation rates (how quickly

the animals mix water from above the sediment into the sediment). We col-

lected boxcores from 19 stations along the transect from the coastal waters of

Alaska to the deep basins of the Barents Abyssal Plain. Because of pressure

effects, remineralization experiments were only performed on cores collected

from less than 2000 m deep.

Macrofaunal biomass was ten times higher than has been previously reported

for the Arctic Ocean, supporting the observations made by other members of the

biology group. Mixing rates of both particles and water were directly corre-

Lisa Clough is with the Department of Biology at East Carolina University in Greenville, North Carolina,

U.S.A. William Ambrose is with the Department of Biology at Bates College in Lewiston, Maine, U.S.A. J. Kirk

Cochran is with the State University of New York at Stony Brook, New York, U.S.A.