The phytoplankton variability in the Pearl River estuary based on VIIRS imagery

A support vector machine (SVM) regression algorithm was developed for estimating the chlorophyll-a concentration (C-chla) in the turbid estuarine waters of the Pearl River estuary (PRE) based on visible infrared imaging radiometer suite (VIIRS) ocean color data. The proposed SVM algorithm outperformed the OC3 algorithm in the turbid waters. The temporal variation and spatial distribution of SVM-based monthly C-chla products were determined during 2012 and 2018. By analyzing the monthly average C-chla products and ancillary data, the underlying mechanisms of the C-chla coastal summer plume jet and winter bloom were revealed. The C-chla coastal plume jet was often observed in June, when the zonal wind direction changed from westward to eastward and the river runoff reached its maximum value of the year. The winter bloom in the ocean area was attributed to strong mixing in the upper layer, which resulted from cooling-induced buoyancy changes.