Xia Jinan Yellow Sea Chlorophyll-a Distribution Characteristics And Environmental Factors

Based on the ecological investigation of South Yellow Sea in the summer of 2008, the spatial distribution characteristics and environmental factors of chlorophyll a were discussed. According to the historical data and the characteristics of environmental factors obtained in this survey, the study area can be divided into 4 districts: Changjiang diluted water area, nearshore water mass area, yellow sea cold water mass area, and mixed water mass area. The distribution of chlorophyll a in different water masses was discussed. Combined with characteristics of different water masses, the influence of environmental factors on chlorophyll a was also analyzed.In the summer of 2008, the average concentration range of chlorophyll a is 0.43-4.54mg/m3 of euphotic zone, and the average is 1.36mg/m3; In general, the value of chlorophyll a is descending from Yangtze Estuary along the Changjiang diluted water; the average value of chlorophyll a in the nearshore area of the west part of the study area is relatively high, while the concentration of chlorophyll a in the middle and east part of Yellow Sea is lower.The distribution of chlorophyll a is controlled by temperature, salinity, light, nutrient and other environmental factors. In summer, nutrient and light is the main controlling factors of chlorophyll a distribution in South Yellow Sea. Temperature and salinity influence the distribution of nutrient by seawater stratification,so they influence chlorophyll a indirectly. The main controlling factor of nutrient in summer is phosphate limitation.In summer, the vertical distribution of chlorophyll a of the samples in Changjiang diluted water area is influenced by halocline. The peak is in upper part water, and the nutrient is the main factor controlling the distribution of chlorophyll a in Changjiang diluted water. In North Jiangsu coastal water, the high value of Chlorophyll a is in upper part water and the controlling factor is light. In yellow sea cold water mass, the distribution of chlorophyll a is influenced by nutrient and light. The peak value is near the nutricline; the core region is at the bottom of euphotic zone; the marginal division is in thermocline, close to the cold water. At mixed area of different water masses, chlorophyll a may have 2 fluorescence peaks in some samples.The spatial distribution of chlorophyll a has 2 accumulation characteristics: peak value in subsurface and in oceanic front area. The reason for peak value in subsurface is mainly due to the seawater stratification in upper part of Yellow Sea cold water, influenced by both nutrient and light. The accumulation of chlorophyll a in oceanic front area is caused by strong vertical mixing, which provides nutrient and light for phytoplankton.