Seasonal distribution of chlorophyll-a concentration in coast of North Yellow Sea

The four investigations of chlorophyll-a in Zhuanghe offshore of North Yellow Sea were carried out in spring,summer,autumn and winter from May of 2008 to Feb.of 2009.In general,the distribution regulation of chlorophyll-a concentration was more complex.The chlorophyll-a concentration was higher in center in Aug.and was increased from south to north in Feb.and from west to east in May and Nov.The chlorophyll-a concentration in surface layer was slightly lower than bottom layer and the seasonal variation was summerwinterautumnspring.It showed typical two peak value pattern,and the summer and winter were two peak periods.In spring,the chlorophyll-a concentration in surface layer was 0.8~3.1 μg/L,the average value was 1.6 μg/L,and in bottom layer was 0.8~2.0 μg/L,the average value was 1.3 μg/L.In summer,that in surface layer was 2.8~15.7 μg/L,the average value was 10.8 μg/L,and in bottom layer was 3.1~16.8 μg/L,the average value was 8.3 μg/L.In autumn,it in surface layer was 0.7~5.7 μg/L,the average value was 2.2 μg/L,and in bottom layer was 0.7~6.0 μg/L,the average value was 2.5 μg/L.In winter,the chlorophyll-a concentration in surface layer was 3.0~13.1 μg/L,the average value was 6.3μg/L,and in bottom layer was 5.2~19.2 g/L,the average value was 10.2 g/L.The environmental factors in better correlation with chlorophyll-a concentration were ammonia salt,salinity and suspended solids of sea water in survey area.