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
Everglades National Park roseate spoonbills ("Platalea ajaja"), ibises and brown pelicans ("Pelecanus occidentalis"), as well as limpkins ("Aramus guarauna") and snail kites that eat apple snails, which in turn feed on the sawgrass. The sloughs' availability of fish, amphibians, and young birds attract a variety of freshwater turtles, alligator ("Alligator mississippiensis"), water moccasin ("Agkistrodon piscivorus conanti"), and eastern diamondback rattlesnake ("Crotalus adamanteus"). Freshwater marl prairies are similar to sloughs but lack the slow movement of surface water; instead, water seeps through a calcitic mud called marl. Algae and other microscopic organisms form periphyton, which attaches to limestone. When it dries it turns into