Epipelagic Zone (Sunlight Zone)

node · earth · Global ocean

The uppermost pelagic layer, conventionally surface to about 200 m. It is the only zone where enough sunlight penetrates to sustain net photosynthesis, so essentially all primary production in the open ocean happens here. The 200 m figure is a convention marking the approximate base of the photic zone in clear open water; it is not a physical boundary, and in turbid coastal water the productive layer can end in tens of metres. Light does not switch off at any depth - it attenuates continuously and roughly exponentially.