11-1 The World Ocean All oceans in the world are connected to form one big ocean. They are broken down into horizontal and vertical zones.

The World Ocean Vertical zones. Photic, aphotic and benthic. Horizontal zones. Oceanic (deep ocean), neritic (near the shore) and intertidal (where shoreline is exposed and submerged depending on tides). Vertical zones. Photic, aphotic and benthic.

Oceanic Zone The open ocean. The largest zone in the ocean. 90% of surface of world’s oceans. Very deep, 500m to 11,000m. Sunlight does not penetrate too deeply into the ocean. Within the oceanic zone, the photic level is about 200m deep. *The phytoplankton (base of photic zone) are producers here. *Zooplankton and small fish consume these phytoplankton. *Bigger fish consume these smaller fish and so on. *Some whales (humpback whale) feed only on the plankton.

Oceanic Zone

Oceanic zone The aphotic zone lies beneath the photic zone. *There is an absence of sunlight here so this limits the biodiversity. (compare this to rainfall limiting biodiversity in the desert) *The organisms that live here feed on detritus (tiny pieces of organic material that are food for organisms at the base of the aquatic food web). This food has drifted down from the surface. It has a rich benthic zone.

Oceanic Zone

Ocean Water Ocean waters differ in their salinity, temperature and density. Ocean water near the equator receives more sun then any other ocean water. *Water is warmer here and more saline and has more minerals because the water tends to evaporate more quickly here. Ocean water near the polar regions (fed by glaciers) is colder and less saline and more dense but still has nutrients. Water in the oceans flow in ocean currents in characteristic patterns driven by the wind.