Euphotic zone

The euphotic zone is the surface layer of the ocean where sufficient light is available for photosynthesis. It extends from the atmosphere-ocean interface downwards to a depth where light intensity falls to 1% of that at the surface (the euphotic depth), so its thickness depends on the extent of light attenuation in the water column. Typical euphotic depths vary from only several metres in turbid estuaries to around 200 metres in the open ocean.