f98u3le1 - Lesson I Environment and Exploration Keywords...

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Lesson I: Environment and Exploration Keywords : algae, epipelagic zone, pelagic, zooplankton, biomass, mesopelagic zone, bathypelagic zone, benthic, habitat, messengers, fluorescence, environment, habitat Environment: Zones Even though the deep sea seems like “just a lot of cold, dark water”, it may be divided into several habitats based on depth and the characteristics of the ocean that vary with depth. These characteristics are shown in your ocean zones diagram. As you move away from shore, the gently sloping continental shelf underlies shallow waters typically less than 600 feet until you reach the continental slope, where the bottom drops away rapidly. The average depth of the ocean is 3800 meters, or 12,445 feet. This fact brings up an interesting point, the earth’s surface is mainly water; in fact, about 71% of the earth is covered by water. Of that 71%, 80% is water greater than 2000 meters (about 6000 feet) in depth. A simple calculation reveals that 57% of the world is deep-ocean! Thus, the deep sea is the “average” environment on earth. It is more typical of our planet than forests, meadows, swamps, or even the seashore. The epipelagic zone . The upper part of the ocean where algae can grow is termed the “epipelagic” zone, and in a clear ocean like the Gulf of Mexico it reaches to a depth of 600 feet. The prefix “epi” means “upper” and the term “ pelagic ” means “open-ocean” or “ocean”. The place where algae can grow is really a thin skin on top of the ocean, yet it is ultimately the source of food for almost everything that lives beneath it. The sun’s light allows the algae to grow, small algae-eating animals consume it, and larger animals may then feed on the algae- eaters. The sun’s energy is thus passed from algae to animals and provides the fuel for our pelagic life in the deep sea. If we look at the ocean zones diagram, the large numbers of algae eaters and other small animals that are collectively called “ zooplankton ” are represented by the kite-like figure labeled biomass ”, which simply means the weight of the zooplankton. The fatter the kite, the more animals there are at that depth. If we move along to the next column in the figure, we can see that there is plenty of light in the epipelagic zone. The last and most complicated part of the figure is the section showing how temperature varies with depth. This temperature diagram is pretty typical of a warm ocean like the Gulf of Mexico in the late spring. At the surface, the temperature is warm, about 25 ° C or 77 ° F, and where the wind has mixed up the ocean it is the
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same temperature from the surface down to 90 feet or, in a strong wind, to as deep as 200 feet. Below this “mixed layer” the ocean begins to get colder as we journey to the… Mesopelagic zone. The mesopelagic zone is the zone known as the middle (meso=middle) ocean, “midwater” or more fancifully, the “twilight zone”. It extends from 600 to 3000 feet. The
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f98u3le1 - Lesson I Environment and Exploration Keywords...

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