gh COLD OF ANTARCTICA BRINGS LIFE TO OCEAN DEPTHS

The contemporary people live in the Age of Mammals (Cainozoe), which was preceded by the Age of Reptiles (Mesozoe) - the epoch of dinosaurs and other prodigious beasts. They have long become extinct, but people with vivid imagination and even some scientists still cherish a hope of finding in the deep ocean waters some monsters, which survived the Age of Reptiles. However, Russian scientists have proved that the ocean waters were practically devoid of life at that remote epoch. A. P. Kuznetsov, research assistant of the P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, summed up the latest achievements of pleitectonics, paleobiooceanology (in particular, history of the planetary climates) and bio-evolution. A. P. Kuznetsov restored the Earth climate changes within the last 65 million years and investigated their impact on the ocean life.

The climate in the Age of Reptiles was constantly warm all over the Earth, the water temperature being about 15-20(C above zero. At such temperatures the atmospheric oxygen scarcely dissolves in the water and does not penetrate the water layer more than several meters deep. Neither does the light get into great depths, therefore the sea weeds photosynthesis is impossible. There is no life without oxygen: fish are unable to breathe in the deep waters and the water animals which need atmospheric air never get that far in the ocean depths as they would not find any food there. Therefore, the warm climate favorable for land species does not suit the deep-water fauna.

The situation changed about 50 million years ago, when having separated from Pangaea, Antarctica 'drifted' away to take its current position. This way Antarctica obstructed the warm ocean waters access to the South Pole and the extensive glaciation process was initiated there. The coastal waters also became cold. The constantly warm climate of the Age of Reptiles was replaced by the zonal climate of the Age of Mammals. As a result, the cold waters rich in oxygen rushed from the cold surface to the warm depths. According to the contemporary assumptions, at that time (as nowadays) Antarctica used to deliver approximately 684,288 cubic kilometers of water annually to the ocean depth. The size of the ocean at that epoch was close to the contemporary one, therefore the late Mesozoic warm waters replacement by the cold Antarctic coastal waters only lasted one and a half or two thousand years. When all the ocean water turned cold, it became suitable for life of the creatures, which needed oxygen, thus enabling the shallow waters inhabitants to migrate into cold waters. The creatures originating from the Antarctica coastal waters were the first to descend into the ocean depth exceeding 3 kilometers. As the continent was 'drifting' towards the South Pole, the creatures were becoming more and more psychrophilic, so they had enough time to adapt themselves to low temperatures. They only had to develop some additional, but not fundamentally new, adaptation capabilities to protect themselves from the high pressure. Practically all the bottom fauna of the ocean depths and the deep-water fish are descendants of the species that once inhabited the southern shallow waters. Antarctic animals were followed by the animals from the low latitudes, which were gradually getting used to the cold-water habitat. Since the environment in the ocean depths is homogeneous (it is dark and cold everywhere), the natural habitat areas of deep-water animals are much larger than those of the surface water inhabitants.

Even the North Pole experienced the influence of the cold coming from the South Pole. The Antarctica area, including the centers of glaciation and the cold ocean, was formed not earlier than eight to ten million years ago. By that time the ocean depths had been already inhabited. Now Arctic is intensively catching up with Antarctic. The amount of the cold water provided by Arctic makes two thirds of that delivered by Antarctic, but the Arctic deep-water fauna is currently being formed and practically does not influence the deep-water species populating the Atlantic and Pacific Oceans.

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