Net community production in the northeastern Chukchi Sea |
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| Institution: | 1. School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 245 O’Neil BLDG, 905 North Koyokuk, Fairbanks, AK 99775-7220, USA;2. Bermuda Biological Station for Research, Inc., 17 Biological Station Lane, Ferry Bermuda, GE01, USA;3. Rosenstiel School of Maine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149-1098, USA;1. Joint International U.Laval-CNRS Laboratory Takuvik, Québec-Océan, Département de Biologie, Université Laval, Québec, Québec G1V 0A6, Canada;2. Sorbonne Universités (UPMC, Université Paris 06)-CNRS-IRD-MNHN, LOCEAN Laboratory, 4 place Jussieu, F-75005 Paris, France;3. Laboratory of Marine Ecosystem and Biogeochemistry, Second Institute of Oceanography (SIO), State Oceanic Administration (SOA), Hangzhou 310012, China;4. Department of Oceanography, Pusan National University, 30, Jangjeon-dong, Busan 609-735, South Korea;1. Department of Oceanography, Pusan National University, 30, Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea;2. Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 406-840, Republic of Korea;1. Department of Environmental Earth System Science, Stanford University, Stanford, CA 94305, USA;2. Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA;3. Marine Science Program & Department of Earth and Ocean Sciences, University of South Carolina, Columbia, SC 29208, USA;4. Emmett Interdisciplinary Program in Environment and Resources, Stanford University, Stanford, CA 94305, USA;5. Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA;1. Stanford University, 473 Via Ortega, Room 140, Stanford, CA 94305, United States;2. Woods Hole Oceanographic Institute, Woods Hole, MA, United States;3. Scripps Institution of Oceanography, La Jolla, CA, United States;1. Department of Environmental Earth System Science, Stanford University, Stanford, CA, USA;2. Ocean Sciences Department, University of California-Santa Cruz, Santa Cruz, CA, USA |
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| Abstract: | To assess the magnitude, distribution and fate of net community production (NCP) in the Chukchi Sea, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), and particulate organic carbon (POC) and particulate organic nitrogen (PON) were measured during the spring and summer of 2004 and compared to similar observations taken in 2002. Distinctive differences in hydrographic conditions were observed between these two years, allowing us to consider several factors that could impact NCP and carbon cycling in both the Chukchi Shelf and the adjacent Canada Basin. Between the spring and summer cruises high rates of phytoplankton production over the Chukchi shelf resulted in a significant drawdown of DIC in the mixed layer and the associated production of DOC/N and POC/N. As in 2002, the highest rates of NCP occurred over the northeastern part of the Chukchi shelf near the head of Barrow Canyon, which has historically been a hotspot for biological activity in the region. However, in 2004, rates of NCP over most of the northeastern shelf were similar and in some cases higher than rates observed in 2002. This was unexpected due to a greater influence of low-nutrient waters from the Alaskan Coastal Current in 2004, which should have suppressed rates of NCP compared to 2002. Between spring and summer of 2004, normalized concentrations of DIC in the mixed layer decreased by as much as 280 μmol kg?1, while DOC and DON increased by ～16 and 9 μmol kg?1, respectively. Given the decreased availability of inorganic nutrients in 2004, rates of NCP could be attributed to increased light penetration, which may have allowed phytoplankton to increase utilization of nutrients deeper in the water column. In addition, there was a rapid and extensive retreat of the ice cover in summer 2004 with warmer temperatures in the mixed layer that could have enhanced NCP. Estimates of NCP near the head of Barrow Canyon in 2004 were ～1500 mg carbon (C) m?2 d?1 which was ～400 mg C m?2 d?1 higher than the same location in 2002. Estimates of NCP over the shelf-break and deep Canada Basin were low in both years, confirming that there is little primary production in the interior of the western Arctic Ocean due to near-zero concentrations of inorganic nitrate in the mixed layer. |
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