Zhang Run, Chen Min, Ma Qiang, Cao Jianping, Qiu Yusheng
Department of Oceanography, Xiamen University, People's Republic of China.
Isotopes Environ Health Stud. 2011 Dec;47(4):489-97. doi: 10.1080/10256016.2011.622442. Epub 2011 Oct 17.
Natural nitrogen isotopic composition (δ(15)N) of suspended particulate organic matter (POM) and nitrogen fixation rates via (15)N(2) 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 δ(15)N 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 N(2) fixation rates showed an increase from the subtropical to the tropical seas. This implies that a higher contribution of (15)N-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 δ(15)N and N(2) fixation rates suggest that the suspended POM δ(15)N may be a potential indicator of nitrogen fixation in surface waters in tropical/subtropical seas.
2005年11月至12月以及2006年3月，在亚洲边缘海（东/南海以及苏禄/西里伯斯/爪哇海）和印度洋东北部沿东经120°、北纬30°至南纬30°的表层水中，测定了悬浮颗粒有机物（POM）的天然氮同位素组成（δ(15)N）以及通过(15)N(2)测定法得到的固氮率。POM的δ(15)N值范围为-1.8‰至12.2‰，平均为3.6‰，在两个半球均显示出向赤道递减的趋势。与此同时，测得的N(2)固定率从亚热带海域到热带海域呈上升趋势。这意味着固氮作用增强导致了更多贫(15)N的POM的贡献。水温以及水柱稳定性是观测到的固氮变化的部分原因。悬浮POM的δ(15)N和固氮率的大规模空间变化表明，悬浮POM的δ(15)N可能是热带/亚热带海域表层水中固氮作用的一个潜在指标。
