Epipelagic

Depth of water

0 - 200 m

Circumstances

Sun light and oxgen are supplied enough but nutrient salts such as P, N, Si are poor. Plankton productivity is very high in the upwelling area and high-latitude area as deep sea water including plenty of nutrient salts is supplied. These planktons are supplied as origins of pelagic and hemipelagic sediments. Plankton productivity in the coastal area is also high as nutrient salts are supplied from rivers. It is approximately 30 Celsius in the low-latitude region including equatro, 10 - 20 Celsius in the mid-latitude region, and 2 - 3 Celsius in the high-latitude region.

Representative upwelling area is off the coast of Peru and California, and equatorial area. In these area, surface seawater is moved away by trade winds and Coriolis force, and deep sea water comes to the surface. As the result, light, oxgen, and nutrient salts are supplied enough, and productivity of planktons such as radiolarians become high. In case trade winds are so weak that deep sea water does not come to the surface, it is called El Niño. In case trade winds are so strong that seawater becomes too cold by the deep sea water, it is called La Niña.

At high-latitude area, cold heavy seawater with high salt concentration is formed at the surface in winter. This heavy seawater goes down and deep sea water including plenty of nutrient salts comes to the surface. As the result, light, oxgen, and nutrient salts are supplied enough in spring, productivity of planktons such as diatoms become high.