Marine life appeared in the form of fish, which live exclusively in water. Some of these evolved into amphibians which spend portions of their lives in water and portions on land. Other fish evolved into land mammals and subsequently returned to the ocean as seals, dolphins or whales. Plant forms such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton, and particularly phytoplankton, are key primary producers forming the general foundation of the ocean food chain. Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters including breathing tubes (see
Arctic National Wildlife Refuge Wildlife Refuge is the only refuge that regularly dens polar bears in that local region, and contains the most consistent amount polar bears in the area. The Arctic basin is the shallowest ocean basin on Earth. It is the least salty, because of low evaporation and large current of freshwater from rivers and glaciers. River mouths and calving glaciers, are continually moving ocean currents contribute to a unique marine ecosystem in the Arctic. The cold, circulating water is rich in minerals, as well as the microscopic organisms (such as phytoplankton and algae) that need them to grow. Marine animals thrive