Without growth and reproduction, life is on hold, not progressing. Salinity can also interfere with an organism's use of water. Fresh water fish cannot live in the ocean, and land plants watered with sea water will die. The excess salt in briny water pulls water out of the organism and dehydrates it. If you put a salt water fish in fresh water it will die, too, because the organism will retain too much water in its cells.
Plants use sunlight for photosynthesis.
Lack of light in caves and under deep water make these environments unsuitable for photosynthesizing plants. Without these chemicals, these cold, dark areas are almost lifeless. These are elements are captured by plants and circulated through food chains. Much of the open ocean is actually a desert because it lacks these nutrients and cannot support life forms. In places where cold water is upwelling from the ocean depths, some of these nutrients are carried up from the ocean bottom, and provide food for life forms at the surface.