Question

How many zones are in the open ocean?
a. 2
b. 3
c. 4
d. 5

Answer 1

A sea or ocean is a waterway that makes much out of a planet's hydrosphere. On Earth, the sea is one of the major regular divisions of the World Ocean. These are the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. The expressions "the sea" or "the ocean" utilized without detail allude to the interconnected group of salt water covering most of the Earth's surface.

Complete answer:
The ocean is divided vertically into different zones from the water surface to the ocean floor. The zones in the ocean are:

• The epipelagic zone or it is also known as the upper open ocean. It extends from the surface upto 200 meters below the surface. It is well-luminated. Hence, many marine organisms can be found in this region, especially seaweeds which require sunlight for photosynthesis.
• The Mesopelagic (200-1000m) zone, which is the place where just limited quantities of light enter, lies underneath the Epipelagic zone. This zone is regularly alluded to as a "Twilight Zone" because of its scant measure of light. Temperatures in the Mesopelagic zone territory from 5-4℃.
• Majority (54 percent) of the sea lies in the Bathypelagic (aphotic) zone into which no light infiltrates. This is additionally called the midnight zone and the profound sea. Because of the total absence of daylight, photosynthesis can't happen and the main light source is bioluminescence.
• Abyss or abyssopelagic zone (4000-6000m) is a home to very few creatures due to the high pressure and low temperature of this zone. Most of the organisms living at this depth are transparent and devoid of eyes.
• Hadopelagic zone or deep ocean trenches and these are around 20,000 feet deep.

Though 5 zones are present, the open ocean consists of the zones above the continental shelf. The zones located above continental shelf are the epipelagic zone, the mesopelagic zone and the Bathypelagic zone.

Hence, the correct answer is option (B).

Note: Sunlight can reach upto 1000m under the water. However, beyond 200m the light intensity will not be significant. Many factors affect the organisms underwater such as temperature, pressure, oxygen level, availability of sunlight etc. Due to these diverse conditions, each zone has different ecosystems with different organisms.