Oceanic zone

The oceanic zone begins in the area off shore where the water measures 200 metres (656 feet) deep or deeper.

It is the region of open sea beyond the edge of the continental shelf and includes 65% of the ocean’s completely open water. The oceanic zone has a wide array of undersea terrain, including crevices that are often deeper than Mount Everest is tall, as well as deep-sea volcanoes and ocean basins. While it is often difficult for life to sustain itself in this type of environment, some species do thrive in the oceanic zone (Col).

Sub zones

The oceanic zone is subdivided into the epipelagic, mesopelagic, and bathypelagic zones.

The epipelagic (euphotic) zone, also called the sunlit zone, receives enough sunlight to support photosynthesis. The temperatures in this zone range anywhere from 40 to âˆ'3 °C (104 to 27 °F)(NHPTV).

The mesopelagic (disphotic) zone, where only small amounts of light penetrate, lies below the epipelagic zone. This zone is often referred to at the Twilight Zone due to its scarce amount of light. Temperatures in the mesopelagic zone range from 5 to 4 °C (41 to 39 °F). The pressure is higher here, it can be up to 1,470 pounds per square inch (10,100,000 Pa) and increases with depth (NHPTV).

90% of the ocean lies in the bathypelagic (aphotic) zone into which no light penetrates. This is also called the midnight zone. Water pressure is very intense and the temperatures are near freezing range 0 to 6 °C (32 to 43 °F)

Marine life

Oceanographers have divided the ocean into zones based on how far light reaches. All of the light zones can be found in the oceanic zone. The epipelagic zone is the one closest to the surface and is the best lit. It extends to 200 meters and contains both phytoplankton and zooplankton that can support larger organisms like marine mammals and some types of fish. Past 200 meters, not enough light penetrates the water to support life, and no plant life exists (NHPTV).

There are creatures however, which thrive around hydrothermal vents, or geysers located on the ocean floor that expel super heated water that is rich in minerals. These organisms feed off of chemosynthetic bacteria, which use the super heated water and chemicals from the hydrothermal vents to create energy in place of photosynthesis. The existence of these bacteria allow creatures like squids, hatchet fish, octopuses, tube worms, giant clams, spider crabs and other organisms to survive (Knight).

Due to the total darkness in the zones past the epipelagic zone, many organisms that survive in the deep oceans do not have eyes, and other organisms make their own light with bioluminescence. Often the light is blue green in colour, because many marine organisms are sensitive to blue light. Two chemicals, luciferin and luciferase that react with one another to create a soft glow. The process by which bioluminescence is created is very similar to what happens when a glow stick is broken. Deep-sea organisms use bioluminescence for everything from luring prey to navigation (Knight).

Animals such as fishes, whales, and sharks are found in the oceanic zone.

Notes

References

• Knight, J.D. (1997) Sea and Sky 25 Oct. 2009.
• "NatureWorks." New Hampshire Public Television - Engage. Connect. Celebrate. Web. 27 Oct. 2009..
• New Hampshire Public Television. "Ocean Zones." Nature Works. New Hampshire Public Television, 2009. Web. 27 Oct. 2009.
• The University Of Delaware Marine Graduate School. "Hydrothermal Vents." Voyage to the Deep. The University of Delaware, 2000. Web. 27 Oct. 2009.