Environmental Factors (continued) - Temperature, Light, Chemical

Temperature -Sun heats the top layer (first meters) -Wind mixes water -Thermocline: boundary between warmer and cooler water. -90% of ocean volume is below the thermocline. <--- know this basic curve.

Light Euphotic Zone -enough light for photosynthesis. -90% of marine life found here ft deep Disphotic Zone -only a small amount of life -no plants, a few animals -greater pressure ft deep -Bioluminescence Aphotic Zone -90% of the ocean -high pressure, cold temp, no light -only life found at ocean vents

Chemicals Salt -estimated 50 million billion tons of dissolved salt in ocean -spread over land surface: a layer 500 ft deep -salt comes from minerals in rocks and volcanic gas; ocean waters evaporate while the salts are left behind.

-72 other natural chemical elements have been identified in ocean waters -Chemicals combine to form insoluble (do not dissolve) products, which sink to the bottom

-Mollusks (oysters, clams, and mussels, for example) extract calcium from the sea to build their shells and skeletons. -Foraminifers (very small one-celled sea animals) and crustaceans (such as crabs, shrimp, lobsters, and barnacles) likewise take out large amounts of calcium salts to build their bodies. -Coral reefs, common in warm tropical seas, consist mostly of limestone (calcium carbonate) formed over millions of years from the skeletons of billions of small corals and other sea animals. -Plankton (tiny floating animal and plant life) also exerts control on the composition of sea water. -Diatoms, members of the plankton community, require silica to form their shells and they draw heavily on the ocean's silica for this purpose. Marine Life and Chemicals