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BIOMES OF THE EARTH - OCEANS Phần 2

The exiting water is rich in minerals and can reach temperatures of 716°F (380°C). Since the late 1970s, when deep-sea hydrothermal vents were seen for the first time, scientists have been fascinated by the startling communities of microbes and animals that live alongside them. | GEOGRAPHY OF THE OCEANS 9 -A heated by volcanic rock until it seeps or bursts out through clefts on the rift valley floor called hydrothermal or hotwater vents from the Greek therme for heat . The exiting water is rich in minerals and can reach temperatures of 716 F 380 C . Since the late 1970s when deep-sea hydrothermal vents were seen for the first time scientists have been fascinated by the startling communities of microbes and animals that live alongside them see Hot vents and cold seeps pages 157-158 . Seas and gulfs People often use the words sea and ocean to mean the same thing. We can talk about going for a swim in the sea or ocean or living in sea-front or an ocean-front property. Technically however a sea is a geographic region of an ocean. For example the Sargasso Sea lies a few hundred miles off the Florida coast in the North Atlantic Ocean. The Sargasso is surrounded by a strong system of currents which marks its boundary with the rest of the ocean. It also contains a unique community of plants and animals floating seaweed and small well-camouflaged fish and other small creatures that live among the weeds. The Sargasso Sea is a distinct part of the North Atlantic. In fact most seas such as the Mediterranean Sea and Caribbean Sea of the North Atlantic are partly or mostly surrounded by land. They are called marginal seas because they lie at the edges margins of the ocean. Gulfs and bays are alternative names for areas of seawater partly enclosed by land as in the case of the Gulf of Mexico or the Bay of Bengal. Parts of an ocean such as the Sargasso Sea have characteristic animal and plant communities because their distinctive environmental conditions allow some organisms to survive there and not others. The community of organisms living in an ocean region also depends upon when and from where animals and plants have colonized that area. If they entered the region millions of years ago and they have become more or less cut off from animals and plants in