南沙群岛海区秋季浮游植物物种多样性及数量变化

根据1997年11月南沙群岛海区的调查资料,对调查海区的浮游植物种类组成、优势种、物种多样性及数量分布特点进行了初步分析。鉴定网采浮游植物共121种,隶属2个门类33属。垂直分层0—75m和75—150m浮游植物细胞数量平均值分别是0.070×104cells·m-3和0.044×104cells·m-3。0—75m层浮游植物细胞数量的高值区出现在调查海区的东部和东南部,最高值出现在安渡滩附近的21号站;75—150m浮游植物细胞数量高值区出现在32号站附近。垂直分布的明显特点是随深度增加浮游植物种类和数量呈减少趋势。三叉角藻Ceratiumtrichoceros和夜光梨甲藻Pyrocystisnoctiluca是0—75m层和75—150m层共有的优势种。0—75m层和75—150m层浮游植物Shannon-Wiener多样性指数平均值分别为3.40和2.07,均匀度平均值分别为0.79和0.60。研究结果表明,秋季浮游植物细胞数量比春、夏季低,浮游植物由硅藻、甲藻组成,甲藻在数量和种类上都占优势。初步探讨了南沙群岛海区秋季浮游植物种类和数量分布与营养盐、温度与盐度、海流及浮游动物等环境因子的关系。     

Spatio-temporal variations in the siphonophore community of the northern South China Sea

To understand how hydrological and biological factors affect near-to off-shore variations in the siphonophore community,we sampled zooplankton at 82 stations in the northern South China Sea during summer,winter,and spring.Forty-one species of siphonophore were collected by vertical trawling.The species richness of siphonophores increased from the nearshore to offshore regions in all three seasons of investigation,with maximum richness in summer and minimum richness in winter.The abundance of siphonophores was also higher in summer than in spring and winter,concentrated in the nearshore region in the warm season and scattered in the offshore region in the cold season.Four siphonophore groups were classified according to the frequency of occurrence:nearshore,near-offshore,offshore,and tropical pelagic.Among them,the nearshore group had higher abundance nearshore compared with the offshore.The tropical pelagic group had higher species number offshore than nearshore.Spatial and temporal fluctuations in taxonomic composition and abundance of siphonophores were due to the influence of the coastal upwelling and surface ocean currents of the South China Sea,driven by the East Asia monsoonal system.     

南海北部上层鱼类浮游生物多样性和丰度的季节变化

The objective of this study was to investigate the seasonal variations of ichthyoplankton diversity and abun-dance in the northern South China Sea based on the data collected during summer, winter and spring. In total, 95 taxa of larval fishes were identified. The greatest number of species was recorded in spring, followed by summer and winter. The number of species was distributed mainly in the coastal waters from the east of Leizhou Peninsula to the southeast of Hainan Island during the surveyed periods of summer and spring, but in the offshore waters during winter. The abundance of larval fish was lowest in winter, increased in spring, and reached the maximum in summer. High abundance of larval fish was generally restricted to coastal waters with the isobaths less than 50 m. Seasonal variations of larval fish richness, abundance and diversity index were significant （P〈0.001）. Carangidae was the most common and abundant taxon in summer and winter, whileSardinella sp.,Thrissa mystax andLeiognathus sp. were dominant in spring. High diversity and abundance of larval fish might be attributed to increased temperature and coastal upwelling in spring and summer.     

南海浮游被囊动物火体虫科(Pyrosomatidae)一新记录种的形态特征

火体虫科(Pyrosomatidae),隶属于脊索动物门、尾索动物亚门、海樽纲、磷海樽目,全球海域已报道8种。本文描述了采自南海火体虫科一新记录种短轮火体虫(Pyrosomella verticillata)群体和单体的形态特征,分析了其群体长度、宽度与轮数的关系,并比较了该种与已在南海发现的大西洋火体虫(Pyrosoma atlanticum)的形态差异。研究标本保存在南海海洋生物标本馆。