南沙海域虫戎群落特征与季风、管水母关系分析

根据2013年3-4月、6-7月、9月和11-12月4个航次的调查资料；分析南沙海域浮游虫戎亚目的种类组成、优势种、栖息密度和群落结构特征；并探讨季风转换对其影响及其与管水母的关系。研究海域内共鉴定浮游虫戎亚目12科26属63种。生态类群结构属于热带大洋性。优势种较少；共出现7种；其中；孟加拉蛮虫戎（Lestrigonus bengalensis）为唯一的年度优势种；优势地位显著。物种组成存在季节性变化；分为春季、夏季与秋-冬季3个群落。虫戎年均栖息密度为18.30×10-2 ind/m3；高数量区主要分布于近岸水域；数量季节变化不明显；但平面分布季节差异明显。虫戎年均丰富度、多样性、均匀度指数和多样性阈值各是1.23、1.28、0.33、0.48。虫戎物种组成随季风转换左右近岸低盐水影响程度而变化；群落结构、生物多样性和栖息密度平面分布随季风转换所驱动的表层环流结构改变而变化。虫戎群落分布与管水母间的相关性证实研究海域两类群物种间的寄宿关系。这种关系促使孟加拉蛮虫戎在沿岸低盐水影响下更易形成高优势度；而表现出类似近岸海域优势种优势地位显著的特点。

Hyperiid community characteristics associated with monsoon and siphonophores in Nansha Islands waters, South China Sea

Hyperiid community characteristics were analyzed using net and concurrent environmental data obtained during seasons of 2013. We evaluated the effect of monsoon changing on hyperrid community and the correlation between hyperiid and siphonophire. We identified 63 species comprised of 26 genera within 12 families for the hyperiid community. This hyperiid community can be divided into three groups:spring group, summer group and autumn-winter group. Hyperiid fauna belongs to the typical tropical ocean region with two ecotypes:the oceanic ecotype with more species and the euryhaline ecotype with higher abundance. Seven seasonal dominant species were Lestrigonus bengalensi, Eupronoe intermedia, E. maculate, Phronima sedentaria, Lycaeopsis zamboanmgae, Tetrathyrus forcipatus and Amphithyrus muratus while L. bengalensi was the annual dominant specieswith noticeable domination. The annual mean of hyperiid abundance was 18.30×10^-2 ind/m³ and annually abundant hyperiid distributed on the continental shelf. The seasonal means of hyperiid abundance were consistent while the seasonal horizontal distributions showed significant differences through seasons. The annual means of hyperiid richness index, diversity index, evenness index and diversity threshold were 1.23, 1.28, 0.33 and 0.48, respectively. Hyperiid composition changed along with the effect of monsoon reversal on the expending and shrinking of coastal hypohaline waters. The horizontal distribution of hyperiid abundance and diversity threshold changed along with the surface currents driven by monsoon reversal. The correlation analysis indicates a symbiosis relationship between hyperiid and siphonophore in Nansha Islands waters. Due to such a symbiosis, L. bengalensi dominates upon the effect of coastal hypohaline waters in-flowed, showing the similarity to the dominant species in coastal ocean.