The spatial and temporal distribution of chlorophyll a and the influencing factors in Shenzhen Bay with frequent occurrence of red tide

From Feb. to Nov. 2008,spatial and temporal distribution of concentration of chlorophyll a were surveyed in four seasons in Shenzhen Bay,and the relationship was analyzed between Chlorophyll-a and main environmental factors. In Shenzhen Bay,the concentration of chlorophyll-a ranged from 3.07 mg·m-3 to 309.94 mg·m-3,with an annual average of 42.29 mg·m-3. The highest av-erage concentration of chlorophyll-a was found in spring (108.33 mg·m-3),followed by that in summer (35.2 mg·m-3),autumn (16.68 mg·m-3) and winter (8.96 mg·m-3) in turn. The concentration of Chlorophyll-a decreased from inner bay to outside bay in winter and spring,while in summer and autumn it decreased from west coast to east coast. The average concentration of Chlorophyll-a declined from inner bay to outside bay throughout the year in this investigation. Correlation analysis showed significant positive correlation between the concentration of Chlorophyll-a and water temperature,COD,TOC,PO43--P,phytoplankton abundance and DIN in Shenzhen Bay,indicating there was close relationship between Chlorophyll-a and these environmental factors. The water body was in serious eutrophication in Shenzhen Bay with the chlorophyll a as assessment criteria implying potential risks of outbreak of red tide at any moment.