The ocean comprises 2/3rd of the Earth’s surface, and is by far the most dominant feature of our world. But what’s in it? Let’s dive in.
Scientists have divided the ocean into 5 different depth zones extending from the surface to the most extreme depths where light can no longer penetrate. As we dive deeper into these less explored places, the temperature drops and pressure increases at an astounding rate.
LIGHT ZONE (0 TO 200 m)
Sunlight streams through the upper zone of the ocean, providing light and energy to the creatures that live there. And there is enough light for photosynthesis to take place. The light zone or epipelagic zone is one which is bright, full of food and is a busy habitat.
This zone contains the vast majority of commercial fisheries. Phyto planktons, usually microscopic occurs in this zone, form the basis of the food chain in the ocean.
TWILIGHT ZONE (200 m to 1000 m)
Deep sea starts where the sunlight starts to fade. This zone is cold and just enough light reaches this zone for animals to see. Many of the animals here are bioluminescent, i.e, they can make their own light to avoid being eaten and to attract prey. Animals in this zone range in size from microscopic to among the largest on planet. This disphotic zone (or poorly lit zone) has a major role in removing carbon dioxide from the atmosphere and storing it, thereby helps to regulate global climate.
DARK ZONE (1000 m to 4000 m)
Sunlight no longer penetrates here. This habitat is immensely cold and the pressure here can crush human bones. Most of the animals living in this zone are black or red in colour due to lack of light. There is continuous shower of droppings from animals above and dead animals and plants here, known as Marine snow. This marine snow is source of food for billions of deep sea creatures.
ABYSSAL ZONE (4000 m to 6000 m)
Water temperature here is near freezing. The continental slope ends here and the sea floor stretches out to be a giant plain. 1/3rd of the seabed lies within this zone. The abyssal plains have mountains, trenches and valleys. Comparatively this zone is very sparsely inhabited because the availability of food is limited.
- Most of the creatures found here are invertebrates such as hagfish and sea pigs.
- The glass sponge Venus flower basket builds its lattice structure in an ingenious manner by gluing silica needles forming a glass like cage structure, referred to as Escape proof prison.
HADAL ZONE (6000 m to 11000 m)
Last but certainly not least, we’ve reached the hadal zone. The oceans plunges to depths greater than 6km in only few places, called trenches. It is the place with no light, immense pressure and no nutrients. The deepest of all trenches is the Mariana trench in Pacific Ocean.
Did you know?
The term Hadal is derived from Hades, the Greek God of Underworld who is considered to be evil.
So much about life in this zone are still unknown because animals collected when brought to surface dies due to the pressure drop. Snailfish is believed to be the deepest living fish currently.
Mysteries of the ocean remain vast and deep, hope we can explore more of this in coming years.
Activity: My Own Deep Sea
Sketch an image of what you imagine the deep sea would look like!