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Grebmeier, J.M., 1988

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Grebmeier, J.M., 1988, The ecology of benthic carbon cycling in the northern Bering and Chukchi seas: University of Alaska Fairbanks, Ph.D. dissertation, 204 p., illust.


Benthic community structure, biomass and carbon cycling in the northern Bering and Chukchi Seas are hypothesized to be regulated by food supplied by variable primary production regimes in the overlying water masses. These water masses transport Pacific Ocean water northward through Bering Strait and across the shelf of the Chukchi Sea. Benthic community structure and metabolism, along with water column and sediment organic carbon, were investigated. Low surface sediment C/N ratios (5.7 - 7.7) suggest a higher quality, nitrogen-rich marine carbon supply to the benthos in the highly productive (~250 g C m-2 yr-1) Bering Shelf/Anadyr (BS/A) water mass compared to lower quality, higher C/N ratios (7.7 - 14.0), indicative of less liable, more refractory marine and terrestrial organic matter, in sediments under the less productive (~50 g C m-2 yr-1) Alaska Coastal (AC) water mass. The benthic communities under BS/A water are dominated by detritus-feeding amphipods (F. Ampeliscidae and F. Isaeidae) and bivalves (F. Nuculidae and F. Tellinidae). A diverse fauna exists under AC water, including a mixture of amphipod (F. Isaeidae and F. Phoxocephalidae), sand dollar (F. Echinarachniidae) and polycheate (F. Sternaspidae and F. Maldanidae) communities. Benthic biomass averaged 20.2 g C m-2 under the BS/A water and decreased to an average 6.3 g C m-2 under the AC water. Total sediment oxygen uptake rates were highest under BS/A water, averaging 19.2 mmol O2 m-2 d-1, and dropped to an average 8.1 mmol O2 m-2 d-1 under the AC water, suggesting a greater organic carbon supply to the BS/A benthos than the AC benthos. Annual benthic carbon consumption associated with BS/A water is estimated at 67.8 g C m-2 yr-1 compared to 27.8 g C m-2 yr-1 in sediments associated with AC water. Combining estimates of zooplankton grazing, microplankton utilization and benthic metabolism, biological consumption accounts for 54% of the BS/A annual carbon production, leaving 46% to be buried in the underlying sediments or transported northward out of the study area. In the AC system all the annual primary production is totally consumed, requiring an external organic carbon source to meet biological demand. The results of the study support the conclusion that the quantity and quality of food supply are major regulating mechanisms in benthic community structure, biomass and carbon cycling in the northern Bering and Chukchi Seas. The seasonally reliable food source leads to stability in this benthic ecosystem in spite of a normally harsh polar environment.

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