南沙群岛海域春、秋季浮游介形类生态学特征

Ecological characteristics of planktonic ostracods in the Nansha Islands waters in spring and autumn

为了解南沙群岛海域春、秋季浮游介形类生态学特征,根据2013年春季(3月中旬至4月初)及秋季(9月)在南沙群岛开展的两个航次生态环境综合调查资料,对该海域浮游介形类生态学特征进行分析研究。结果显示:(1)南沙群岛海域浮游介形类物种组成较为丰富,记录45种隶属于2科、4亚科、19属。其中,春季有21种,秋季38种,两季均出现的共有种有14个;(2)春、秋两季浮游介形类优势种差异明显,春季优势种组成较为单一,数量低,主要生态类群为外海暖水类群和广温暖水类群,秋季优势种组成较为复杂,数量多,主要为外海暖水类群。春季优势种由后圆真浮萤、葱萤、尖头毛浮萤组成,秋季由纳米海萤、双叉真浮萤、刺喙葱萤、短形小浮萤、粗大后浮萤组成。研究表明:(1)春秋两季浮游介形类密度差异显著,密度分布不均,局部区域密度较高,与该海域局部环流密切相关;(2)浮游介形类两季平均丰富度、多样性指数和均匀度分别为0.59、1.37和0.55,秋季高于春季;(3)春季及秋季均分为岛礁群落和外海群落,群落分布随洋流改变呈季节性变化;(4)受季风影响的大环流及局部环流是浮游介形类种类组成、数量分布及多样性呈明显季节差异的主要因素。

This study aims to analyze and compare the community structure of planktonic ostracods assemblages between Nansha reef area and open water area, and the distribution pattern influenced by ocean current movement was discussed. During April and September in 2013,27 sampling stations were set up in Nansha Islands Waters, and planktonic ostracods were collected at depths from 200 m to the surface using medium plankton net. Samples were treated and counted according to the standard methods. The results are the following findings： （1）A total, of 45 planktonic ostracods species were identified, belonging to 19 genera,4 subfamilies, and 2 families. Twenty-.one species only occurred in spring and 38 species only in autumn,and 14 species occurred in both seasons. （2）The dominant species were different between two seasons ;Euconchoecia maimai, Porroecia porrecta, and Conchoecetta acuminata dominated in spring, while Cypridina natal, Euconchoecia bifurata , Porroecia spinirostris , Microconchoecia curta , Metaconchoecia macromma dominated in autumn. All dominant species are either eurythemal-euryhaline or warm-hyperhaline. Studies show that, （ 1 ） There are remarkable differences in the density of planktonic ostracods between two seasons. In spring, density ranged from 0.03 to 8.25 ind/m3 , averaging 1.4 ind/m3 ; in autumn, density ranged from 0.05 to 18.92 ind/m3 with an average of 4.11 ind/m3. High density occurred in certain limited areas due to ocean circulation. In spring, three high density areas were located in the west, northwest and southeast corners of Nansha Islands waters, respectively. In autumn high density area occupied the vast east part. （2） Species richness,diversity and evenness were 0.59,1.37 and 0.55, respectively, with much higher values in spring than in autumn. （3）Planktonic ostracods can be divided into two communities in both seasons characterizing, reefs and open waters, and seasonal variation in community distribution was impacted strongly by ocean current change. （4）The tropical cyclonic and anticyclonic circulation driven by monsoon can be regarded as the dominant factor to influence the structure of planktonic ostracods community.