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Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. Oceanic trenches are prominent, long, narrow topographic depressions of the ocean floor. They are typically 50 to 100 kilometers (30 to 60 mi) wide and 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic ...
In the ocean, the aphotic zone is sometimes referred to as the dark ocean. Depending on how it is defined, the aphotic zone of the ocean begins between depths of about 200 m (660 ft) to 800 m (2,600 ft) and extends to the ocean floor .
Pelagic zones. The ocean can be conceptualized as being divided into various zones, depending on depth, and presence or absence of sunlight.Nearly all life forms in the ocean depend on the photosynthetic activities of phytoplankton and other marine plants to convert carbon dioxide into organic carbon, which is the basic building block of organic matter.
Natural light does not penetrate the deep ocean, with the exception of the upper parts of the mesopelagic.Since photosynthesis is not possible, plants and phytoplankton cannot live in this zone, and as these are the primary producers of almost all of earth's ecosystems, life in this area of the ocean must depend on energy sources from elsewhere.
Very little is known about the microbial community of the mesopelagic zone because it is a difficult part of the ocean to study. Recent work using DNA from seawater samples emphasized the importance of viruses and microbes role in recycling organic matter from the surface ocean, known as the microbial loop .
“The Southern Ocean is very stormy in general (but) in the Drake you’re really squeezing (the water) between the Antarctic and the southern hemisphere,” he adds. “That intensifies the ...
Organisms at these hydrothermal vent systems are in the aphotic zone of the ocean and have adapted to very low light conditions. Studies on deep sea shrimp have shown the potential for flood lights used on the sea floor used in studying the vent systems to cause permanent retinal damage, [ 116 ] warranting further research into the potential ...
“It’s very hard to do research on marine mammals if you don’t see them at sea,” she said. “It’s a bit of a needle in a haystack. You don’t know where to look.”