南海西北部浮游生物中多孔放射虫的组成与分布

Species composition and distribution of polycystine radiolarians (Protozoa) in the plankton from the northwestern South China Sea

对南海西北部海区1959年全年各月所取得的浮游生物小网样品中的放射虫进行了定量研究,分析了其种类组成和分布,结果表明,所鉴定出的212种多孔放射虫主要为热带大洋暖水种,其中泡沫虫目(Spumellaria)145种,占总种数的68%,罩笼虫目(Nassellaria)67种,占总种数的32%;泡沫虫目无论在种类和数量上均较罩笼虫目占优势.研究海域的主要优势种为海绵球虫(Spongosphaera streptacantha)、钟翼盔虫(Pterocorys campanula)、四房面包虫四房亚种(Om-matartus tetrathalamus tetrathalamus)、三臂星虫(Triastrum aurivillii).该海域放射虫的全年密度分布状况变化很大,1,2月放射虫密度较小,分布范围也较小,3月起数量增多,4,5,6月是全年密度较大的月份,出现许多斑块状密集区,7,8月数量有所减少,其他月份密度也相对较小.放射虫数量变化总的趋势为春末夏初较多,秋季较少,冬季最少.放射虫的丰度和种类多样性在调查海域变化复杂,但基本趋势是从西北和北部向东南部由低逐渐升高;由海南岛周边海域和广东沿海向外海由低逐渐升高;此分布格局主要受海流、温度、盐度、深度和营养盐等环境因子的影响.

The species composition and distribution of polycystine radiolarians in the plankton from the northern South China Sea are analyzed based on the samples collected with Judy net by the natioanl comprehensive oceanographic survey of China in 1959 from 128 stations. Two hundred and twelve species belonging to the orders Spumellaria and Nassellaria are identified, in which, 145 species （68%） are members of Spumellaria, and 67 species （32%） belong to Nassellaria, and most of them are warm-water species. The species and individual number of Spumellaria are much more than those of Nassellaria in the area. Four species, i.e., Spongosphaera streptacantha Haeckel, Pterocorys campanula Haeckel, Ommatartus tetrathalamus tetrathalamus Haeckel, and Triastrum aurivillii Cleve, are considered as dominant species, by their ranges and the individual proportion in the total individual number （more than 3 %）. The results show the variation of radiolarian distribution pattern seasonally. The individual density and distribution range of radiolarians are the lowest and the narrowest in January and February; the abundance increases from March, the density reaches the highest in April and remains in May and June, and forms several high density centres; the density decreases from July and August to December. That is to say, radiolarians breed largely and are abundant in late spring and summer, then the populations of species reduce in autumn and become down to the lowest in winter. The results also imply that the abundance and species diversity of polycystine radiolarians enhance from coast to open sea gradually. This distribution pattern is affected by the water currents, temperature, salinity, and depth.