Ocean Zones

It is in the epipelagic zone, from the surface to 650 ft (200 m) (corresponding to the euphotic zone), that phytoplankton (algae and microscopic plants) live. They are the primary producers of the ocean, the lowest level on the oceanic food web. Using the process of photosynthesis, they convert carbon dioxide, water, and other nutrients to the simple carbohydrates, providing food for themselves and for higher organisms.

On the next level upward in the pelagic food web are the primary consumers, the zooplankton (microscopic animals). They feed on phytoplankton and, in turn, become food for larger animals (secondary consumers) such as sardines, herring, tuna, bonito, and other kinds of fish and swimming mammals. At the top of this food web are the ultimate consumers, the toothed whales. (A baleen whale's diet consists mostly of plankton).