The character of chlorophyll-a and its grey relationship with nitrate in the Pearl River estuary in summer

Based on the data of chlorophyll-a, nitrate and nitrite derived from the samples collected from the Pearl River estuary during 2004 to 2008, the spatial-temporal character of chlorophyll is analyzed and the correlation between chlorophyll-a, nitrate, and nitrite is studied using Grey System Theory. The distribution of chlorophyll has significant annual variation. There are two high chlorophyll regions, lying around the Wanshan Islands and the Qi'ao Islands, and the high chlorophyll distribution always exists near the Wanshan Islands during all the observed years. There is a good grey correlation between chlorophyll and nitrite, especially around the Qi'ao Islands. From the Lingding Sea to the Shenzhen coast, the grey correlation is not as significant as that in other regions. Except for the Humen and Shenzhen bay stations, all the other stations have a positive degree of grey relation. The sign of the grey relation degree between chlorophyll and nitrate has an obvious spatial difference, with a negative correlation near the coast and a positive correlation in the estuarine region.