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
Freshwater inflow supports beaches and provision the inter-tidal wetlands. Organic material delivered to estuaries by freshwater inflows the primary energy source for organisms living in the estuary. Estuarine ecosystems need freshwater inflow to maintain their productivity, or to continue to produce biomass. Estuarine ecosystems are fundamentally important and necessary to protect through the management of freshwater inflow because of the many ecosystem services they produce. An ecosystem service is something provided by nature that is of value to humans. Estuarine ecosystems are among the most productive ecosystems on the planet. Estuaries house such species as the blue crab, red fish, flounder, spotted