Underwater light field of the Mediterranean Sea

The waters of the Mediterranean Sea are less blue and less green than the waters of the global ocean due to low chlorophyll concentration and a relatively high amountof yellow substance (CDOM). Bio-optic classification defined this sea as Case 1 water, at least in summer. Due to this low chlorophyll concentration, the euphotic depth, calculated as the depth reached by 1% of surface light, is 123 m (in the Levantine).However, based on the depth of the deep chlorophyll maximum (DCM) at 80-150 m, it appears that in many cases, the euphotic depth is probably closer to the depth reached by 0.1% of the surface light (which can be 185 m). The distribution of the phytoplankton, including Synechococcus and Prochlorococcus, is the result of their cell size, pigment concentration, photoacclimation, and photoadaptation, as well as sensitivity to sunlight and UV, which is high most of the year in this sea. However, since phytoplankton distribution both affects and is affected by the bio-optic properties of the Mediterranean Sea, the prediction of future distributions in response to climate change is not straightforward.