The phytoplankton size class (PSC) plays an important role in biogeochemical processes in the ocean. In this study. a regional model of PSCs is proposed to retrieve vertical PSCs from the total minus water absorption coefficient (at-w(λ)) and Chlorophyll a concentration (Chla). The PSC model is developed by first reconstructing phytoplankton absorption and Chla from at-w(λ). https://foldlyers.shop/product-category/stands/