Application of GOCI to the mapping of phytoplankton size structure around Korean peninsula

Phytoplankton controls marine ecosystems in terms of nutrients, photosynthetic rate, carbon cycle, etc. and the degree of its influence on the marine environment depends on their physical size. Many studies have been attempted to identify marine phytoplankton size classes using the remote sensing techniques. One of successful approach was the three-component model which estimates the chlorophyll concentrations of three phytoplankton size classes (micro-; >20 μm, nano-; 2-20 μm and pico-; <2 μm) as a function of total chlorophyll. Here, we examined the applicability of Geostationary Ocean Colour Imager (GOCI) to the mapping of the phytoplankton size class distribution in the Korean waters. A fit of the three-component model to a biomarker pigment dataset collected in the East Sea for some years including a large harmful algal bloom period has been carried out to derive size-fractioned chlorophyll concentration (CHL). This demonstrated the conceptual framework of the three-component model holded even at extremely high total chlorophyll concentrations with a dominance of large cells, and supports the application of the three-component model to the regions around the Korean Peninsula. The tuned three-component model was applied to the hourly GOCI images to identify the fractions of each phytoplankton size class for the entire CHL. Then, we investigated the diurnal variations in phytoplankton community in terms of the size structure in the East Sea during the harmful Cochlodinium polykrikoides blooms in the summer of 2013.