6.S.II.1

"Marine life Life zones are determined by the depth to which light can penetrate making photosynthesis possible, and by the availability of nutrients. The bottom (benthic zone) extends from sunlit continental shelf to dark sparsely populated depths. Shallow lighted water extending over continental shelf contains 90% of marine species. Pelagic zone: water in open oceans Classification of marine life Bottom-living (benthic) such as kelp and mollusks Free-swimming (nekton) such as fish and whales Small drifting plants and animals (plankton), which are the dominant life and food source of the ocean The basis for most marine life is phytoplankton (plant-plankton), which carry on photosynthesis near surface; contrast zooplankton (animal plankton). Most deepwater life depends on rain of organic matter from above. The densest concentration of marine life is found in surface waters, such as those off Chile, where nutrient-rich water wells up to the bright surface. "