Latitudinal distribution of nitrogen isotopic composition in suspended particulate organic matter in tropical/subtropical seas |
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| Authors: | Run Zhang Qiang Ma Jianping Cao Yusheng Qiu |
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| Institution: | 1. Department of Oceanography , Xiamen University , People's Republic of China;2. Department of Oceanography , Xiamen University , People's Republic of China;3. State Key Laboratory of Marine Environmental Science , Xiamen University , People's Republic of China |
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| Abstract: | Natural nitrogen isotopic composition (δ15N) of suspended particulate organic matter (POM) and nitrogen fixation rates via 15N2 assay were measured in surface waters along 120° E from 30° N to 30° S in the Asian marginal seas (the East/South China Seas and the Sulu/Celebes/Java Seas) and the northeastern Indian Ocean in November–December 2005 and March 2006. The POM δ15N values ranged from?1.8 to 12.2‰ with an average of 3.6‰ and showed a decreasing trend towards the equator in both hemispheres. In parallel, the measured N2 fixation rates showed an increase from the subtropical to the tropical seas. This implies that a higher contribution of 15N-depleted POM was derived from enhanced N2 fixation. Water temperature and the stability of water column were partly responsible for the observed variations in nitrogen fixation. The large-scale spatial variations in suspended POM δ15N and N2 fixation rates suggest that the suspended POM δ15N may be a potential indicator of nitrogen fixation in surface waters in tropical/subtropical seas. |
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| Keywords: | Asian marginal seas isotope biochemistry isotope ecology nitrogen-15 N2 fixation northeastern Indian Ocean |
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