中文摘要：

根据2002-2003年长江口29°00′-32°00′N、122°00′-123°30′E海域4个季节的调查，运用定量、定性方法，探讨了长江口及邻近海域浮游介形类总丰度的平面分布、季节变化、丰度变化与水团的关系，以及优势种的环境适应和优势种丰度对介形类总丰度的贡献；并与东海外海的分布特征进行了比较．结果表明，该海域浮游介形类总丰度具有明显的季节变化，春季最高，夏季次之，秋季最低．四季多样性指数（H’）均低于2，其中冬季最高，夏季最低．共出现浮游介形类20种，春季最多（16种），秋季最少（3种）．四季皆为优势种的仅有短棒真浮萤（Euconchoecia chierchiae），其它的主要有后圆真浮萤（E．maimai）和针刺真浮萤（E．aculeata）等．春季的后圆真浮萤和冬季的短棒真浮萤对总丰度的贡献最大（β〉O．90）．短棒真浮萤的分布对总丰度的季节变化有重要影响，由此形成介形类特有的变化特征．图5表3参20

英文摘要：

Based on the data from four seasonal oceanographic surveys in the Changjiang Estuary （29°00′-32°00′N and 122°00′-123°30′E） from 2002 to 2003, the seasonal alteration and horizontal distribution of ostracod abundance, as well as the relationship between the ostracod abundance and water masses were studied. Moreover, the environment adaptation of dominant species and their contribution to total ostracod abundance were discussed. The distribution pattern of pelagic Ostracoda was compared with that of the offshore in the East China Sea. The results showed that the seasonal abundance of pelagic Ostracoda differed obviously in the studied waters, and it was highest in spring and lowest in winter. The diversity indices （H＇） of pelagic Ostracoda in four seasons were all below 2.00, and the highest was found in winter and the lowest in summer. A total of 20 species of pelagic Ostracoda were identified. The species number of pelagic Ostracoda peaked （16 species） in spring, but only 3 species were found in autumn. Euconchoecia chierchiae was the dominant species in four seasons. In spring Euconchoecia maimai was the most important species for its great contribution to total abundance （β〉0.90）. In winter E. chierchiae was the only dominant species with contribution to total abundance above 0.90. The abundance of E. chierchiae greatly affected the seasonal abundance of ostracods, thus determining the ecological variation of pelagic Ostracoda in the studied areas. Fig 5, Tab 3, Ref20