热带、亚热带太平洋和南印度洋束毛藻的大尺度分布研究

利用2008年大洋环球航次,研究了热带、亚热带太平洋和南印度洋中束毛藻丰度的大尺度分布特征,结果表明:在亚热带西北太平洋和热带东南亚海域束毛藻藻丝平均丰度较高,分别为25.2×103和33.3×103m-3,在热带中太平洋、热带东太平洋和南印度洋束毛藻平均丰度较低,分别为1.76×103,0.87×103和1.52×103m-3。各海区束毛藻丰度与水温无明显相关关系。总叶绿素a的分布特征与束毛藻不同,在太平洋呈西低、东高,在热带东南亚海域较高而在南印度洋较低,从总叶绿素a的粒级结构看,微微型浮游植物(0.2~2μm)所占比重最高,其次是微型浮游植物(2~20μm),小型浮游植物(20μm)所占比重最低。各海区束毛藻对总叶绿素a贡献的比例不同,在亚热带西北太平洋和热带东南亚海域较高,分别占总叶绿素a的7.79%和3.92%,在热带中太平洋、热带东太平洋和南印度洋占总叶绿素a的比例较低,均低于1%。在亚热带西北太平洋束毛藻固氮占真光层总新氮输入量的比例较高,这是该海域新氮的重要来源之一,而在热带中太平洋和热带东太平洋束毛藻固氮对真光层新氮的贡献比例则很低。

The large-scale distribution of Trichodesmium in the tropical and subtropical Pacific Ocean and the southern Indian Ocean

Trichodesmium abundances were studied in the tropical and subtropical Pacific Ocean and the southern Indian Ocean from May 2008 to February 2009. The study area was divided into five districts including the northwest subtropical Pacific (NWSP), the central tropical Pacific (CTP), the eastern tropical Pacific (ETP), the tropical southeast Asia sea areas(TSAS) and the southern Indian Ocean (SIO). Results show that Trichodesmium trichome abundances vary between 0 and 130 103 m-3. The average abundances of Trichodesmium in the TSAS and the NWSP are 33.3 103 m-3(5.75×103~130×103 m-3) and 25.2×103 m-3(2×103~81.3×103 m-3) respectively, which are higher than in the CTP, the ETP and the SIO, where average abundances of Trichodesmium are 1.76 103 m-3(0~10.3×103 m3), 0.87×103 m3(0~7.75 103 m-3) and 1.52×103 m-3(0~8 103 m-3) respectively. No correlation between the surface water temperature and Trichodesmium abundance were found, however, iron flux from atmosphere seemed to be a hint to Trichodesmium abundances, which need to be studied further. Total chlorophyll a(chl a)concentration had a different distribution characteristics from Trichodesmium abundances, which was lower in the NWSP and the SIO but higher in the CTP, the ETP and the TSAS. The phytoplankton community was composed mostly of picophytoplankton, chl a in the 0.2~2 μm size fraction accounted for more than 60% of the total chl a, while Trichodesmium chl a made up a very small proportion of total chl a. N₂-fixation rates of Trichodesmium are estimated, N₂-fixation by Trichodesmium is greeter than 30% new nitrogen sources in the NWSP but much lower in the CTP and the ETP.