Bathyal zone

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The bathyal zone or bathypelagic is the pelagic zone that extends from a depth of 1000 to 4000 meters below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The average temperature hovers at about 4 °C (39 °F). Although larger by volume than the Euphotic zone, the bathyal zone is less densely populated. Sunlight does not reach this zone, meaning there can be no primary production. It is known as the midnight zone because of this feature. Because of the lack of light, some species do not have eyes, but one of the species that does is the viperfish. Another is the frill shark. Many forms of nekton live in the bathyal zone, such as squid, large whales, and octopuses, but this zone is difficult for fish to live in. Sponges, brachiopods, sea stars, and echinoids are also common in the bathyal zone. The fish in this zone have become very energy efficient since it is especially hard to find nutrients. Many have slow metabolic rates, to conserve energy. The fish here have weak muscles, soft skin and slimy bodies. Animals in the bathyal zone aren't threatened by predators that can see them, so they do not have powerful muscles. There are few plants because of lack of sunlight, as they need sunlight to produce their food through photosynthesis.The Bathyal zone holds some of the world's largest whales.

The Bathyal Zone is the benthic zone that extends from the shelf-edge (about 70 to 250 m) to about 3000 meters below the ocean surface. The upper limit of the Bathyal Zone lies at the continental shelf-break, defined by physical, geological and biological characteristics. The Circalittoral, the deepest faunal zone on the continental shelf, extends down to the lower limit of multicellular algae, that is also the upper limit of the Bathyal. Although of primary importance, because of major gradient changes, the shelf-edge sector remains a poorly known environment because it lies between two distinct zones of interest, the coastal-shelf environment and the deep realms. Thus, it is not surprising that the shelf-to-slope transition remains a biological and physical "no man's land”. This limit is independent of that of the phytal - aphytal zones, which is related to the transparency of the waters. In the same way there is no relation between the upper Bathyal limit and the Exclusive Economic Zone (EEZ) previously limited at 200 m depth. This depth has no scientific justification, just an economical one. However there is often a confusion about. The Bathyal zone extends along the continental slope until the Abyssal rise at about 3000 m.

[edit] References

• Enig, C. C. (1997). "Bathyal zones on the Mediterranean continental slope: An attempt" in Research on marine benthos: 9^th Iberian Symposium on Studies of Marine Benthos.: 23–33, Madrid: MAPA, SGT. ISBN 8449102995.