Life is found thousands of meters deep in the ocean, far from the reach of sunlight. Special types of life are found surrounding chimney-like vents that release hot water rich with minerals. The photic zone layer is where most marine life exists. The depth of the photic zone layer is not constant because the angle of the incoming sunlight varies from day to day and seasonally. The photic zone extends to the seafloor in many areas of the coastal ocean.
Productivity is greatest in zones of high temperature gradients called ocean fronts.
Energy flows through the food chains. Photosynthesis Photosynthesis is the production of organic substances, cheifly sugars, from carbon dioxide and water, in green plant cells that are supplied with enough light. Oxygen is released to solution during photosynthesis and consumed during respiration. Some types of bacteria can convert carbon dioxide and water to organic matter by using energy from chemical reactions rather than light. This process is called chemosynthesis .