Bathyal Zone

The Bathyal zone is the marine ecologic realm that extends down from the continental shelf to the depth where the water temperature is 4°C (which is 39°F). Both these limits are variable number, but the bathyal zone is normally described as a surface which lies between 200 and 2,000 m (that is 660 and 6,600 feet) below the surface area.

In this section, we will know about Bathyal Zone in detail.  

Bathyal Zone 

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In the Bathyal waters, photosynthesis does not occur as the zone is being characterized as a dark zone except in the clear, virtually lifeless waters of the tropics. In these tropic regions, small amounts of sunlight can penetrate deep as 600 m (2,000 feet). The temperatures in higher latitudes range from approximately 3° to -1° C (that is 37° to 30° F). Except for this place, the normal temperatures range between 5° and 15° C (that is 41° and 59° F), the western oceanic margins are warmer, this is because of the current from the equatorial region and from the eastern margins which receives colder boreal currents and also experiences upwelling. The salinities typically range between 34 and 36 parts per thousand in the bathyal zone. While it varies with local conditions of water-mass formation. The Bathyal fauna reflects how the narrow ranges of temperature and salinity occur.

At the bathyal depths, here the currents are exceedingly slow, also in many areas, the bathyal waters are quite deeper than 1,000 m (that is 3,280 feet) this water is essentially stagnant, which results in low oxygen concentrations and impoverished faunal levels.

Though in the upwelling and counter-currents can create favourable conditions for aquatic life like fish and other organisms. In some middle- to high-latitude areas, the number of individuals in this bathyal faunal assemblage is generally only half as large as in the shallow-water fauna. This has been demonstrated. However, the single-habitat species diversity is higher for the bathyal fauna. This condition is caused by the constancy of the bathyal environmental conditions, moreover about the temperature. The bottom dwellers in the zone with adequate circulation get adapted to the local substrate conditions. The terrigenous bottoms which are located near the continents support the most abundant suspension and it is a home for the mud-eating populations. The cold-water bathyal corals are here found in the sub-Arctic to the equatorial regions.

Bathypelagic Zone 

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The bathyal zone or the bathypelagic zone, which means ‘midnight zone. This is the part of the open ocean that extends from a depth of about 1,000 to 4,000 m (that is 3,300 to 13,100 ft) this lies below the ocean surface. This zone lies between the mesopelagic above and the abyssopelagic which lies below.

The bathypelagic zone is the worldwide zone of deep ocean waters, which is about 3,000 to 13,000 ft (this is 1,000–4,000 m) below the surface. This is inhabited by a wide variety of marine forms, this includes eels, fishes, molluscs, and other organisms.

Bathyal Zone Animals 

To know about the Bathyal Zone organisms living there we need to dive deeper into the ocean which is located between 3,300 to 13,000 feet measured in depth. Above this zone lies the mesopelagic zone, below is located in the abyssal zone also known as the abyssopelagic zone. The bathyal zone is a permanent darkened zone, with a little amount of sunlight at the blue end of the spectrum which penetrates as far down the bathyal zone. The lack of light present here in this zone along with the water pressure here contributes to the living condition for the aquatic life living here.  

Many fishes which live in this bathyal zone are either black or red in colour. This colour acts as a defence mechanism as in the darker zone the red skin colour of the aquatic organism appears to be black and hence predators cannot find them easily. 

Primary production of plant life is minimum, so all the creatures that live here are main carnivores who feed on each other. Examples: Hagfish that have rasping mouthparts by tearing the flesh from the carcasses, the viperfish which have large eyes which help them to detect their prey, and scavenger sharks like the frilled shark or the sleeper shark. Some other fishes attract their prey with bioluminescent lures which include dragonfish and the angler fish.

Another important fish type living in this zone is the Eels. They have long, thin bodies which are adaptable to the pressure conditions in the bathyal zone. The two most common species among them are the swallower eel and the gulper eel. These eels have large mouth lines coupled with teeth. This feature helps them to accommodate the prey which is larger than themselves. While the monognathid eel had developed a single fang that is linked to a primitive venom gland on which it impales its prey.  

Bathyal Zone Temperature

In the bathyal zone, the marine ecologic realm extends down from the edge of the continental shelf towards the depth where the water temperature is 4° C (that is around 39° F). Both these temperature limits are quite variable, yet the bathyal zone is generally described as lying between the 200 and 2,000 m (which is 660 and 6,600 feet) below the surface area.