Monday, May 12, 2008

Deep sea and trenches


The deepest recorded oceanic trenches measure to date is the Mariana Trench, near the Philippines, in the Pacific Ocean at 10924 m (35838 ft). At such depths, water pressure is extreme and there is no sunlight, but some life still exists. Small flounder (family Soleidae) fish and shrimp were seen by the American crew of the bathyscaphe Trieste when it dove to the bottom in 1960.
Other notable oceanic trenches include Monterey Canyon, in the eastern Pacific, the Tonga Trench in the southwest at 10,882 m (35,702 ft), the Philippine Trench, the Puerto Rico Trench at 8605 m (28232 ft), the Romanche Trench at 7760 m (24450 ft), Fram Basin in the Arctic Ocean at 4665 m (15305 ft), the Java Trench at 7450 m (24442 ft), and the South Sandwich Trench at 7235 m (23737 ft).
In general, the deep sea is considered to start at the aphotic zone, the point where sunlight loses its power of transference through the water. Many life forms that live at these depths have the ability to create their own light.
Much life centers on seamounts that rise from the deeps, where fish and other sea life congregate to spawn and feed. Hydrothermal vents along the mid-ocean ridge spreading centers act as oases, as do their opposites, cold seeps. Such places support unique biomes and many new microbes and other lifeforms have been discovered at these locations