中文摘要：

在长江口附近和浙江近海海域,近些年来每年春季几乎都发生大规模的东海原甲藻（Prorocentrum donghaiense）赤潮,时间通常是在4月底或5月初,但2005年却一直到5月底才发生。本文根据近几年在浙江近海进行的多个春季航次的调查资料和有关站位的气象资料,分析了该海区2005年春初的温度特征及其对大规模东海原甲藻赤潮发生的影响,阐明了2005年春季大规模东海原甲藻赤潮迟发的主要物理环境原因。结果表明,2005年3月浙江近海水温比多年同期平均值偏低,且这种情况在近岸区更为明显;与2004年同期相比,2005年春初（4月初）浙江近海水温偏低,2005年和2004年的这种水温差异在近岸和中上层的低盐水里最为明显,而在远岸和下层的高盐水水温差异则相对要小;近岸低盐水最低温度2005年比2004年低约2.6℃;2005年1—3月浙江近海特殊的气象条件（10 a中最低的气温和强劲的偏北大风）和2004/2005年冬季较弱的台湾暖流是形成4月初浙江近海低温特征的主要原因;2004年冬季和2005年春初浙江近水温偏低很可能是2005年春季东海大规模原甲藻赤潮迟发的主要原因。

英文摘要：

In spring of recent years,a large scale harmful algae bloom（HAB） of Prorocentrum donghaiense nearly occurs annually in the end of April or beginning of May in the Zhejiang coastal and off Changjiang estuary region,however,it did＇t occur until the end of May of 2005.Temperature characteristic in the study area in early spring of 2005 and its influence on a large scale HAB of Prorocentrum donghaiense are analyzed on the basis of survey data carried out in spring of 2002-2005 and some related historical meteorologic data.The results show that water temperature in March 2005 is obviously lower than that of 15-year-averaged（1985-2001） in Zhejiang coastal sea,especially in nearshore region of Zhejiang coastal sea,compared to the same period of 2004,water temperature in early spring（early April） 2005 is about 2.6 ℃ lower.Special meteorologic conditions（the lowest air temperature in the past ten years and strong northern monsoon）and feeblish Taiwan Warm Current in winter of 2004/2005 are the main causes of low water temperature in investigated area.Low temperature characteristic may be main causative factor that a HAB of Prorocentrum donghaiense in spring 2005 occurred late which differ from that of Spring 2002—2004 in Zhejiang coastal sea.