Sublittoral

The sublittoral is divided into two subzones — the upper sublittoral with the lower boundary passing at a depth of 6-10, sometimes 25 m, and the lower sublittoral. In the upper sublittoral, well-lit by the sun ( euphotic zone ), plant hydrobionts usually prevail, and in the tropical zone - reef-forming corals . In the lower sublittoral, which is largely related to the dysphotic zone , bottom living organisms predominate in biomass. There is no generally accepted clear pattern of vertical biological division of the ocean floor even within the continental shallow, therefore, the definitions of the sublittoral zone and its maximum depths vary in different sources ^[1] . Often, the lower boundary of the sublittoral zone is attributed to maximum depths from 40-50 m in the northern seas, to 200, and sometimes 500 m, in tropical seas with a high degree of transparency of water. Sometimes the lower boundary of the sublittoral is tied to the lower boundary of the distribution of attached macrophyte algae ( phytal ). The average depth of the lower boundary of the sublittoral passes along the isobath about 130-140 m.

The sublittoral borders in its upper part with the littoral , along with which they occupy the entire continental shelf, or the mainland, and in the lower part, with the bathyal corresponding to the mainland slope. The width of the sublittoral varies depending on the width of the shelf and can range from several tens or hundreds of meters (the southwestern part of the Bering Sea , the Sea of ​​Okhotsk , the Black Sea ) to several hundred kilometers, both in the north-eastern part of the Bering Sea and on the eastern coast of South America in the area of ​​the Argentinean Patagonia . The greatest width of the shelf (sublittoral) - up to 1400 km, is observed off the Arctic coast of Canada in the Canadian Arctic archipelago and in northern Europe in the Barents Sea - up to 1000 km. The total sublittoral area occupies 27.5 million km², or 7.6% of the world's oceans ^[2] .

Significant sublittoral areas, which are also considered as offshore zones, may also be present in the so-called microcontinent - the plateau of Madagascar , the Seychelles bank and the banks of the Saya de Mallia in the Indian Ocean , and in the area of ​​the New Zealand plateau in the Pacific Ocean , which are characterized by similar to the continents, the structure of the earth's crust with a granite layer.

Environmental conditions in the sublittoral zone and the corresponding neritic zone of the pelagic zone , in comparison with the zone of the open ocean, are the most optimal for the life of many marine organisms. Sublittoral waters are characterized by a wide range of temperature and salinity fluctuations. There is a sufficient amount of nutrients , and hydrological, temperature and gas regimes favorable for life are supported. Due to this, the sublittoral is the richest part of the shelf in terms of biodiversity , which accounts for the maximum biomass of bottom plants and benthic animals, reaching 10-15 in the upper subzone, and sometimes even 20-30 kilograms per 1 m² of bottom area, and from a few in the lower subzone grams up to 100-300 g / m², and sometimes up to 700 g / m² ^{[3] [4]} . The richest fishing zone of the World Ocean is also located here, where up to 80% of all fish stocks are concentrated and where (according to 1969 data) about 12.5 million tons of fish and 4.5 million tons of non-fish products are harvested ^{[5 ]} .

For the name of the corresponding sublittoral of the coastal “shelf” zone of oceanic volcanic islands and underwater elevations ( underwater ridges and guyots ) with a depth of less than 200 m, the lower underwater slopes of which belong to the thalassobathial and the coastal pelagial to the pseudoneric zone , the equivalent term is used - thalassosublitoral , or thalasso ^[6] .

The term “sublittoral” is also used in some schemes of ecological zoning of the bottom of lakes ^[4] .

• Sublittoral. Biological Encyclopedic Dictionary (inaccessible link) . Retrieved July 16, 2013
• Biology of the Pacific. Sublittoral. (unavailable link) Retrieved July 16, 2013
• Website: Underwater World. Retrieved July 16, 2013