Most ocean food chains depend on phytoplankton as primary producers. Where in the ocean do phytoplankton live? within about 200 meters of the ocean surface, because phytoplankton require light to survive within about 200 meters of the ocean shoreline, because phytoplankton depend on nutrients that wash into the water from land throughout all ocean waters, because phytoplankton can tolerate a wide range of temperature and light conditions attached to shells along the ocean floor, because phytoplankton cannot float