There are two main types of aquatic ecosystems: marine ecosystems, which cover 71% of the Earth's surface, and freshwater ecosystems, which cover 0.78%. Freshwater ecosystems can be divided into lentic (slow moving water like ponds and lakes) and lotic (faster moving water like streams and rivers). Wetlands are a type of freshwater ecosystem dominated by plants adapted to saturated soil, including swamps, marshes, fens, and bogs. Aquatic ecosystems perform important functions like recycling nutrients, purifying water, providing habitat, and are used for tourism.