Abyssal (8)

 

The Abyssal Zone, also known as the Abyssopelagic Zone is the part of the ocean which is typically characterized by uniform darkness, low temperature (around 3 degrees celsius), and unique fauna. It lies between the Bathyal Zone and Hadal Zone. It roughly starts at a depth of 4,000 m (13,000 ft) and ends at 6,000 m (19,500), which is where the Hadal Zone,  begins. The latter is primarily made up of deep trenches, like the Mariana Trench of the Challenger Deep fame.

In the absence of photosynthesis, the oxygen content of this zone depends on the oxygen that gets dissolved into the water in polar areas and makes it to the other parts of the ocean.

Its nutrient salt concentration is uniform―at times, higher than what it is in shallow water; courtesy, the dead biological matter that settles in this zone.

Animals of the Abyssopelagic Zone

• ·   The ability to withstand tremendous amount of pressure is a necessity. 
• The animals inhabiting this zone seem to excel in this context.·        
• As there is no sunlight to support the process of photosynthesis, the Abyssal Zone is devoid of plants. 

Crustaceans living at these depths have adapted by becoming transparent and have evolved without eyes because they serve no purpose at these depths.

Tiny microbes( cormophytes) act as producers in this zone by resorting to the process of chemosynthesis and oxidizing hydrogen sulfide coming from vents in the ocean floor.

Tubeworms are best suited for the conditions prevailing in the Abyssal Zone. They don't have mouth or digestive system. So they absorb inorganic compounds through their skin and depend on bacteria in their body for food.

Examples of abyssal zone animals


 giant squid (Architeuthis dux),

 colossal squid (Mesonychoteuthis hamiltoni)

black swallower (Chiasmodon niger) 

humpback anglerfish (Melanocetus johnsonii)

 deep-sea glass squid (Teuthowenia pellucida)

 ogrefish (Anoplogaster cornuta),
 
hagfish (Eptatretus cirrhatus),

 hydrothermal vent crab (Bythograea thermydron),

 giant tubeworm (Tevnia jerichonana), 

Fish in this zone:

·         various physical and behavioral adaptations to survive.

·        

·         The humpback anglerfish (Melanocetus johnsonii), for instance, has a large mouth with long teeth, which helps it grab its prey the moment it is in close range.

 Other physical adaptations include gray or black color, (camouflage) in the deep sea environment,

·         Bioluminescence( ability to produce light by physiological processes) which helps the species lure their prey.

·         ambush predators(wait for their prey to come to them), instead of expending energy chasing them.

·       This zone is characterized by the presence of hydrothermal vents, also known as black smokers that release toxic chemicals. Interestingly, the area around these vents is known for its rich biodiversity. The organisms found here resort to chemosynthesis for energy.

Other animals of the abyssopelagic zone include basket stars, seapigs, and seaspiders. Basket stars are echinoderms with an arm span larger than 25 cm living on the ocean floor or on another animal, feeding on detritus floating down from above. The seapig is another echinoderm that looks like an ugly sea cucumber and can eat mud like an earthworm. Some echinoderms, like the swimming cucumber, use wing-like structures to swim as if they were flying through the water. The sea spider is a crustacean and actually resembles a spider walking on the ocean floor. The sea spider has a hose-shaped mouth and eats anemones and echinoderms. Its leg span reaches 30 cm or larger