中文摘要：

根据2006年4月和2011年4月两个航次的调查数据,对比分析了桑沟湾水域春季水温、盐度及溶解无机氮（DIN）、活性磷酸盐（PO34-）、活性硅酸盐（Si23--Si）含量的时空分布特征,探讨了目前大面积赤潮暴发的可能原因。结果显示,2011年的氮、磷、硅浓度都高于2006年同期调查结果,分别是2006年的5.6倍,1.3倍和3.2倍。氮磷比高达（66.33±47.16）,硅磷比为（35.12±21.44）,硅氮比为（0.82±0.77）,严重偏离Redfield比值。块状分布明显,氮、磷、硅的空间分布情况相似,都是在湾口的东南部（褚岛外海）有高值区,向湾内递减;在湾底的西北部赤潮的始发区,有次高值区,与盐度的低值区几乎重叠。从营养盐、水文、大型藻类营养盐竞争与克生作用及水温4个方面,分析了赤潮暴发的可能原因。

英文摘要：

There are over 20 years of history of shellfish and seaweed polyculture in Sungo Bay.There had not been reported the outbreak of red tide in the Bay.However,in May 2011,there occured large scale red tide outbreak,which almost spread over the total bay,and which caused higher mortality of cultivated shellfish.It is very important to understand the cause of red tide and to provide data for future environmental protection and aquaculture management.We just carried out one survey of environment monitoring before the outbreak of the red tide.Therefore,in this paper,the distributions of sea water temperature,salinity and dissolved nutrients were investigated in Sungo Bay in April 2006 and 2011,so as to understand the cause of the outbreak of red tide.The results showed that the concentration of dissolved inorganic nitrogen（DIN）,phosphate（PO3-4）and silicate（Si）in Sungo Bay of 2011 was 5.6,3.2 and 1.3 times of the same period in 2006,respectively.The mole ratio of DIN/P,Si/P and Si/DIN was（66.33±47.16）,（35.12±21.44）and（0.82±0.77）,respectively,which was seriously deviated from the Redfield ratio.Dissolved nutrients showed obvious block distribution,their horizontal distribution was characterized by a concentration decrease from the open sea to the inner bay,and there were two sub-peak values near the Yatou River and Bahegang areas,the isolines were almost overlaps with low-salinity isolines.The probable causes of red tide outbreak were discussed from four aspects including nutrients,hydrological characteristics,kelp and temperature.