Wetlands are areas of land submerged in water near both terrestrial and aquatic systems. They are highly diverse and are classified by the United States Fish and Wildlife Service into five categories: “The term wetland includes a variety of areas that fall into one of five categories: (1) areas with hydrophytes and hydric soils, such as those commonly known as marshes, swamps, and bogs; (2) areas without hydrophytes but with hydric soils - for example, flats where drastic fluctuation in water level, wave action, turbidity, or high concentration of salts may prevent the growth of hydrophytes; (3) areas with hydrophytes but nonhydric soils, such as margins of impoundments or excavations where hydrophytes have become established but hydric soils have not yet developed; (4) areas without soils but with hydrophytes such as the seaweed-covered portion of rocky shores; and (5) wetlands without soil and without hydrophytes, such as gravel beaches or rocky shores without vegetation”.
Wetlands can also be classified based on salinity, a type of classification often referenced in research where salinity is a major factor. These classifications are often referred to in parts per thousand (ppt) and include freshwater (0-2 ppt), intermediate (2-10 ppt), brackish (10-20 ppt), and saltwater (20+ ppt).