The Dynamic Variation Of Chlorophyll A Concentration And Algal Community In Qinhuangdao Coastal Area

An investigation was carried out from September 2013 to September 2014 in Qinhuangdao coastal area.We studied the variation characteristics of temperature and salinity, the spatial and temporal distribution of chlorophyll a concentration, species composition and abundance variation of phytoplankton, and correlation analysis among temperature, salinity, chlorophyll a and phytoplankton, in order to provide a basis for further research on ecological conditions and prevention of the occurrence of red tide and brown tide.The annual average temperature is 13.23?. The overall trend of spatial distribution of temperature is decreasing gradually from near shore to far shore. The salinity is stable during the whole year and maintains at about 29. The salinity is low in the near shore. The farther from the shore, the higher sanility is.The annual average concentration of total chlorophyll a, 20—200?m size- fractionated chlorophyll a, 5—20?m size- fractionated chlorophyll a and 0.7—5?m size- fractionated chlorophyll a is 6.15mg/m³, 1.88mg/m³, 2.09mg/m³ and 2.56mg/m³ respectively. The spatial distribution of total chlorophyll a and size- fractionated chlorophyll a is decreasing gradually from near shore to far shore. The contribution of 0.7—5?m size- fractionated chlorophyll a to total chlorophyll a is higher than any other size- fractionated chlorophyll a, which accounts for 39.17% and 36.12% in surface and bottom water repectively.In total, 3 phylum, 35 genus and 80 species of phytoplankton are identified in Qinhuangdao coastal area. Bacillariophyta has the largest number of species, 24 genus and 49 species. The number of species changes a lot in different months and there is a largest number of species in July 2014. The average value of the abundance of phytoplankton during investigation is 1.49×10⁸ cells·m^-3. The abundance of diatoms and dinoflagellates is 1.35×10⁸ cells·m^-3 and 2.07×10⁷ cells·m^-3 respectively. The abundance of phytoplankton is decreasing gradually from near shore to far shore. The dominant species are Lauderia borealis, Ditylum brightwellii, Leptocylindrus danicus, Eucampia zoodiacus etc. The diversity index varie s from 1.27 to 3.77, and the evenness from 0.31 to 0.78.The correlation analysis shows that there is a significant positive correlation between temperature and total chlorophyll a from March to September 2014. With regard to temperature and phytoplankton abundance, there is a significant positive correlation in September 2013, February to April and June to September 2014. The chlorophyll a concentration and phytoplankton abundance both have a very strong negative correlation with salinity. The abundance of diatoms has a significant positive correlation with 20—200?m size- fractionated chlorophyll a concentration. But the abundance of dinoflagellates has weak correlation with three kinds of size- fractionated chlorophyll a concentration.