INCREDIBLE LIFE IN THE DEEP SEA

INCREDIBLE LIFE IN THE DEEP SEA

Oceans cover about 75% of the world's surface and 90% of the seas lie beyond the shallow continental margins. Most oceans are deeper than two kilometers and are home to some of the most diverse life on the earth.

We are familiar with animals that live on the surface of the ocean where sufficient light penetrates and photosynthesis takes place in plants. Unlike the surface zone, however, the deep-sea zone is a habitat with pretty inhospitable living conditions. The pressure there is so immense that we would be crushed if we go down there! The temperature is nearly freezing; food is very scarce and there is no light at all!

In addition, the sea floor in some regions consists of volcanic areas, which release fluids that are hundreds of degrees hotter and sometimes may even contain toxic substances that kill organisms still manage to survive in such hostile conditions! These creatures have evolved body structures, behaviours and body chemistries that enable them to survive in such unusual environments.

 

Oceanic Depths

Oceanographers divided the open ocean or pelagic zone into five layers:

1. The epipelagic zone: The first layer that extends up to 200 meters. It is the photic zone or sunlit zone that receives sunlight.

 

2. The mesopelagic zone: The second layer also known as the dim light zone or twilight zone. This extends from 200 m to 100 m and forms the border of the photic zone above and darker zone below.

 

3. The bathypelagic zone: The deep sea starts from hereafter. This is the third layer extending from 1000 m to 4000 m. the sunlight doesn't penetrate deep into this layer. Hence this zone is also called midnight zone.

 

4. The abyssopelagic zone: This is the fourth layer extending from 4000 m to sea floor. The name of this zone comes from a Greek word meaning "no bottom" and refers to the ancient belief that the open ocean was bottomless! The water here is almost freezing and its pressure is immense.

 

5. The hadal zone: This zone includes waters found in the ocean's deepest trenches.

 

Survival Strategies

The deep-sea creatures tolerate or avoid extreme conditions by adopting a variety of survival strategies. Some of the most interesting strategies are given here.

 

i) Tolerating Pressure: This is a serious problem for deep-sea animals. The pressure increases about one atmosphere (atm) for every 10 m we descend into the ocean. So at 100 m, pressure will be about 11 atm. At such a high pressure, only pressurized submersible vehicles can give us protection. Without such protection, the enormous pressure can cause serious damage due to the presence of large air spaces inside our bodies. However, this immense pressure has little effect on the animals living in this region, as they have bodies that are completely filled with water! Many fishes have a swim bladder that contains gases. The volume of gases in the bladder can be adjusted as they move up and down.

 

ii) Bioluminescence: This is an extraordinary feature exhibited by the animals living in deep seas. It is a chemical process that results in the release of light through specialized organs called light organs. Light is produced either through symbiotic bacteria living on the fish or through specialized self-luminous cells called photophores.

 

Bioluminescence occurs when certain chemicals are mixed together. At least two chemicals are required to produced bioluminescence. The first one is known as a luciferin. This is the chemical that actually creates the light. The second chemical is called luciferase, an enzyme that actually catalyzes the chemical reaction. When these chemicals are mixed together in the presence of oxygen, light is produced. A by-product of this process is an inert substance called oxyluciferen.