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Variation of Nitrate Concentrations and δ 15N Values of Seawater in the Drake Passage, Antarctic Ocean

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Title
Variation of Nitrate Concentrations and δ 15N Values of Seawater in the Drake Passage, Antarctic Ocean
Other Titles
남극해 드레이크해협 해수의 질산염 농도와 질소동위원소 값의 변화
Authors
Keun, Khim Boo
Yi Wang
장양희
Hong, Chang-Su
Sigman D
Shin, Hyoung Chul
Subject
Oceanography
Keywords
nitrate; nitrogen isotope; isotope effect; Drake Passage; Antarctic Ocean
Issue Date
2008
Citation
Keun, Khim Boo, et al. 2008. "Variation of Nitrate Concentrations and δ 15N Values of Seawater in the Drake Passage, Antarctic Ocean". Korea Institute of Ocean Science & Technology, 30(4): 407-418.
Abstract
Seawater samples were collected at discrete depths from five stations across the polar front in the Drake Passage (Antarctic Ocean) by the 20th Korea Antarctic Research Program in December, 2006. Nitrate concentrations of seawater increase with depth within the photic zone above the depth of Upper Circumpolar Deep Water (UCDW). In contrast, δ 15N values of seawater nitrate decrease with depth, showing a mirror image to the nitrate variation. Such a distinct vertical variation is mainly attributed to the degree of nitrate assimilation by phytoplankton as well as organic matter degradation of sinking particles within the surface layer. The preferential 14NO3- assimilation by the phytoplankton causes 15NO3 concentration to become high in a closedsystem surface-water environment during the primary production, whereas more 14NO3 is added to the seawater during the degradation of sinking organic particles. The water-mass mixing seems to play an importantrole in the alteration of δ 15N values in the deep layer below the UCDW. Across the polar front, nitrate concentrations of surface seawater decrease and corresponding δ 15N values increase northward, which is likelydue to the degree of nitrate utilization during the primary production. Based on the Rayleigh model, the calculated ε (isotope effect of nitrate uptake) values between 4.0 and 5.8 were validated by the previously reported data, although the preformed δ 15NO3 initial value of UCDW is important in the calculation of ε values.
URI
http://repository.kopri.re.kr/handle/201206/6672
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