Latitudinal distribution of nitrogen isotopic composition in suspended particulate organic matter in tropical/subtropical seas
- 海洋环境－已发表论文 
Natural nitrogen isotopic composition (delta N-15) of suspended particulate organic matter (POM) and nitrogen fixation rates via N-15(2) assay were measured in surface waters along 120 degrees E from 30 degrees N to 30 degrees 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 delta N-15 values ranged from -1.8 to 12.2 parts per thousand with an average of 3.6 parts per thousand and showed a decreasing trend towards the equator in both hemispheres. In parallel, the measured N-2 fixation rates showed an increase from the subtropical to the tropical seas. This implies that a higher contribution of N-15-depleted POM was derived from enhanced N-2 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 delta N-15 and N-2 fixation rates suggest that the suspended POM delta N-15 may be a potential indicator of nitrogen fixation in surface waters in tropical/subtropical seas.