Seasonal and decadal shifts in particulate organic matter processing and sedimentation in the Bering Strait Shelf region |
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| Institution: | 1. Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, WA 98105, United States;2. Resource Ecology and Fisheries Management Division, Alaska Fisheries Science Center, NOAA Fisheries, 7600 Sand Point Way NE, Seattle, WA 98115, United States;1. Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, Bremerhaven 27570, Germany;1. College of Fisheries and Ocean Sciences, University of Alaska, Fairbanks, AK 99775, USA;2. ASL Environmental Sciences, Inc., #1-6703 Rajpur Place, Victoria, B.C., Canada V8M 1Z5;3. North Slope Borough, Department of Wildlife Management, P.O. Box 69, Barrow/Utqia?vik, AK 99723 USA;1. NOAA Fisheries Office of Science and Technology, 7600 Sand Point Way NE, Seattle, WA 98144, USA;2. NOAA Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98144, USA;3. Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD 20688, USA;4. Institute of Marine Sciences, University of Alaska, Fairbanks, AK 99775, USA;1. Woods Hole Oceanographic Institution, Woods Hole, MA, USA;2. Department of Earth System Science, Stanford University, Stanford, CA, USA;3. Pacific Marine Environmental Laboratory, Seattle, WA, USA;4. University of Maryland Center for Environmental Science, Solomons, MD, USA;5. National Oceanic and Atmospheric Administration, Silver Spring, MD, USA;6. Polar Research Institute of China, Shanghai, China;7. Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan;8. Institute of Ocean Sciences, Sidney, British Columbia, Canada |
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| Abstract: | We present data on the quality and quantity of particulate organic material deposited to the benthos in the Chukchi Sea. This analysis is undertaken by using 7Be, a short-lived radiotracer, which is associated with particle deposition, the stable carbon isotopic composition of organic material and its C/N ratio in the water column and within the sediments, and the inventories of chlorophyll a present in surface sediments. Using previously published data, we show that sedimentation processes in the regional Bering Strait ecosystem may have shifted in the past decade. Surface sediments collected in 2004 adjacent to the Russian coastline in the Chukchi Sea are less refractory in terms of carbon isotope ratios and C/N ratios than was observed for surface sediments at similar locations in 1995 and 1988. Based upon sediment 7Be and chlorophyll a inventories, short-term sedimentation on the shelf occurs immediately north of Bering Strait, and within and downstream of Barrow and Herald Canyons. Seasonal differences (i.e., ice-covered versus open-water conditions) in the quality of particulate organic carbon reaching the benthos appear to be small in the most productive waters, such as Barrow Canyon. However, in less productive waters, C/N ratios and δ13C values show seasonal variations. Once on the bottom, δ13C values in the organic fractions of the sediments are less negative than observed in settling material in the water column, which is commonly thought to result from biological processing within the sediments. |
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