长江口北支轮虫群落结构周年变化特征

Annual variation of rotifer community structure in the northern branch of the Yangtze River Estuary

2010年10月_2011年9月，对长江口北支水域轮虫和水体理化因子进行了调查。共采集到轮虫19种，隶属于7科，17属，以腹尾轮虫科、腔轮科和臂尾轮科为主。舞跃无柄轮虫和针簇多肢轮虫出现频率高。其中，春季、秋季和冬季的优势种皆为舞跃无柄轮虫，夏季的优势种则为针簇多肢轮虫。轮虫年平均密度为1．40±1．11ind·L-1，各月平均密度的变化范围为0．2—4．4ind·L-1，秋季最高（2.25±1．7ind·L-1）冬季最低（0．93±0．69ind·L-1），距入海口最近采样点（S5）轮虫全年密度最低（1．00±0．67ind·L-1）。应用Primer软件，对每月轮虫的群落密度进行聚类分析和MDS分析，两者分析结果一致，1、2、3和9月轮虫密度相近，5、8和11月差异不大。CCA分析表明，盐度是影响轮虫群落结构变化的主要环境因子。

A study was conducted from October 2010 to September 2011 to understand the rotifer community structure in the northern branch of the Yangtze River Estuary. A total of 19 species of rotifers were found. These species belong to 7 families and 17 genera. Brachionidae, Lecanidae and Gastropodidae were the most common families. Ascomorpha saltans and Polyarthra trigla were common species. A. saltans was the dominant species in spring, autumn and winter, whereas P. trigla was dominant in summer. The average density of rotifers for the whole year was 1.40±1.11 ind. L-1. The monthly average density varied from 0.2 to 4.4 ind · L-1, with the highest density values occurring in autumn （2.25±1.7 ind · L-1） and the lowest density values in winter （0.93±0.69 ind · L-1 ）. The average density of rotifers was the lowest （ 1.00±0.67 ind · L-1 ） at station 5 closer to the mouth of the river. Hierarchical clustering and MDS were applied to analyze the rotifer community structure, revealing two main groupings, one with data from January, February, March and September, and another with data from May, August and November. The CCA analysis showed that salinity was the main environmental factor affecting the rotifer community structure.