The relationship between deep-sea waters and benthic organisms beyond the continental shelf and their environment.In a broad sense, the term "deep sea" usually includes three parts: deep sea, abyssal and hadal.100 m below the ocean is the absolute dark environment, where the transmission energy of sunlight is about 1% of the surface.There is a lack of sunlight in the deep sea, and the hydrostatic pressure is high, forming a dark, low temperature and high pressure environment.Due to the inability to carry out photosynthesis, there are no photosynthetic plants, no phytophagous animals, only herbivorous and carnivorous animalsHeterotrophic microorganismAnd a small amountFilter feeding animal。Deep sea ecosystemIt is mainly divided into deep-sea hydrothermal ecosystem and deep-sea cold spring ecosystem[1]。
In the 1830s, some countries in Northwest Europe began to investigate and collect deep-sea organisms, but in the 1840s, many people still believed that there was no life in the deep sea.E. Forbes believes that there is no life in the sea area below 550m, and calls the sea area below 550m as an inanimate zone.In 1860, engineer J. Fleming found attached single corals and other animals on the submarine cable 2000m deep in the Mediterranean Sea, and then denied this inference.Since then, many countries have carried outDeep-sea organismSurvey.However, the research on deep-sea ecology has notthe Second World WarIt was fully launched after the end.The global deep-sea survey conducted by the "armored shrimp" survey ship led by A. Bruen of Denmark, the deep-sea survey conducted by the "Warrior" survey ship led by the Soviet UnionDeep-sea animalsThe ecological investigation has found a large number of new animal groups that have not been recorded in the past, and benthos have been found in the deepest ocean, including deep-sea trenches more than 10000 meters long.Since the 1960s, the application of new technologies and means, such as submarine photography and deep submersibles, has brought the research of deep-sea ecology to a new stage.The French Archimedes and the American Alvin deep submersibles carried out deep sea surveys, especially the latter's deep sea surveys and studies near the Galapagos Islands in Central America and the Gulf of California in the eastern Pacific Ocean, and achieved significant results[2]。
Deep-sea animalsThe species and quantity of are relatively poor.But many large animal groups are represented in the deep sea (see table).Most of the species of some groups inhabit the deep sea, such as Pogonophora and Isopoda, of which 75% to 83% are deep-sea species, greatly exceeding the species in intertidal zone and shelf area.The dominant groups living in the ultra abyssal zone include bearded brachial animals, echiurida, Holothurias and isopods.The number of species of some groups, such as fish, tunicata, cirripedia, bryozoa and spongia, decreases significantly with the increase of depth;Decapoda, Brachiopoda and Turbolaria have not been found in the abyssal zone with a water depth of more than 6000m.Generally speaking, the species of deep-sea animals are quite different from those in shallow waters, showing obvious regional characteristics, especially in low latitude waters.For example, only 12% of the genera living off the Carolina coast are found in the waters of the continental slope, and only 5% are found in the waters of the continental shelf.
Number of deep-sea animals
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The quantity (biomass) distribution of deep-sea animals is closely related to the food sources on the seabed.There are abundant benthos in the deep sea adjacent to the continental shelf and the deep sea floor of the high productivity area.For example, in the western Bering Sea near Kamchatka Peninsula, the biomass is up to 30g/m2 at a depth of 4000m.But for the whole Pacific Ocean, the benthic organisms are very poor, and the number of marine benthos is very low. The biomass of most sea areas is below 1 g/m2.According to the estimation of the Soviet Union's Н Vinogradova in 1962, the sea area with a depth of more than 3000 m accounts for 77.1% of the total sea area, while its benthic biomass only accounts for 0.8% of the total marine benthic biomass, with an average of 0.2 tons per square kilometer.Therefore, the deep sea is called the "desert" in the ocean.The vast majority of deep-sea animals feed on organic detritus, which belongs to herbivores, and a small number of carnivores.Therefore, some scholars use the different proportions of herbivores and carnivores as the basis for dividing different deep-sea animal communities.The number of deep-sea zooplankton is very small. For example, in the water layer with a depth of 6000~8000m from Qiandao to Kamchatka Trench, the biomass of plankton is only 0.1% of that of the water layer with a depth of 50m on the surface.Compared with surface zooplankton, deep-sea zooplankton has a wide geographical distribution.This is because the temperature and salinity of deep seawater change little.
Ecological adaptation
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Animals living in 200~1000m water depth have bright colors, such as some shrimps are red or purplish red.Animals living in the water depth of more than 2000m are mostly dull in color, for example, some sea cucumbers are grayish white or black[2]。
Visual organ
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The visual organs of deep-sea animals have evolved in two directions: the visual organs of a few species have developed significantly to adapt to extremely weak light, such as Synaphobranchus in fish;The eyes of other species degenerate or disappear completely, such as blind fish, pentacheles and Nephropsis living in 5000m depth of the North Atlantic Ocean.In the latter case, its tentacles are often very developed, such as shrimps with long whiskers.The blind fish without tentacles often use their lateral line system to sense the low-frequency sound waves in the sea water in order to find food and escape from enemies.
limbs
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In order to adapt to living on the bottom of deep-sea ooze and avoid being trapped in the ooze, sea spiders (Pycnogonida) and some isopods have special limbs;handleCrinoids, sponges, sea gills, sea squirts and other animals that live fixedly extend their stalks to support their bodies;Benthosaurus stretches its pectoral and caudal fins to support its body. Marine organisms adapt to the marine environment by constantly evolving their bodies.
bones
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Because the temperature at the bottom of the ocean is low and the pressure is high, which affects the precipitation of calcium carbonate in animals, the calcareous shells, bone needles and bones of deep-sea animals form slowly. Their shells are thin, brittle or soft, such as the soft bones of soft sea urchins and few or no bone fragments of deep-sea sea cucumbers.
Feeding organ
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In order to adapt to the characteristics of food scarcity in the deep sea, some deep-sea fish have huge mouths and can swallow food several times larger and many times heavier than themselves;Some fish have sharp teeth;Some of them have fishing rod like or fishing line like bait organs, with luminous structures at the ends, which act as bait (see marine nekton)[2]。
Illuminator
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Many deep-sea animals in dark environments often have light-emitting organs or tissues.Many shrimps, sakura shrimps, especially cephalopods, have light-emitting devices with complex structures, which can emit strong cold light. We will study dark unknown creatures with better technology in the future.
Reproductive mode
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Poor food and low temperature conditions have a great impact on the reproduction of deep-sea animals, so the reproduction of deep-sea animals is diverse and special:
① Like the shallow sea animals, they produce a large number of small eggs and have the planktonic larva development stage of the sea surface animals.
② It produces a small number of eggs with large size, and develops into adults in a very short time or directly into adults.
③ Some deep-sea animals are viviparous or oviparous, such as snaketails, sea cucumbers andChondrichthyesThe deep-sea species.
④ Some male fish are very small and parasitize on female fish to facilitate mating and fertilization, such as fish (Ceratias holbolli).
Submarine hot springBiomeFrom 1977 to 1979, the American submersible Alvin investigated the submarine hot springs near the Galapagos Islands and found newDeep-sea organismCommunity.Among themFilter feeding animalMainly.The seawater from the hot spring is rich in hydrogen sulfide and sulfate;Sulfide bacteria are very abundant, with a density of 106/ml.These bacteria carry out the primary production of organic matter by chemical synthesis and provide food for filter feeding animals.The animals in this community include bivalves (one of which has a shell length of 30cm) that filter organics and bacteria, armored shrimp, giant tubular animals (more than 2m long) that coexist with bacteria, and hot spring organisms such as small crabs, tube jellyfish, some gastropods and red fish.They constitute a special ecosystem, known as "deep sea oasis".This is an important achievement in deep-sea ecological research[2]。
