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
Harmful Algal Bloom and Hypoxia Research and Control Amendments Act of 2013 accumulation in the population of algae (typically microscopic) in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Freshwater algal blooms are the result of an excess of nutrients, particularly some phosphates. Harmful algal blooms are algal bloom events involving toxic or otherwise harmful phytoplankton such as dinoflagellates of the genus "Alexandrium" and "Karenia" or diatoms of the genus "Pseudo-nitzschia". is an algal bloom that causes negative impacts to other organisms via production of natural toxins, mechanical damage to other organisms, or by other means. HABs are often associated with large-scale marine mortality events and