A freshwater ecosystem is a type of aquatic ecosystem with a low salt concentration. It includes lakes, ponds, springs, rivers, streams and wetlands. It may be divided into two categories: the lentic or still water ecosystem and the iotic or the flowing water ecosystem.
Lakes and ponds belong to the lentic ecosystem. These bodies of water can range from a few square meters to hundreds and thousands of square miles. The largest lake, Lake Baikai in Central Asia, makes up about one-fifth of the freshwater on Earth. Lakes and ponds usually have little species diversity and are isolated from other bodies of water.
Streams and rivers are bodies of flowing water running in one direction. The water from the iotic ecosystem originates from springs, melted snow in the mountains, and even lakes. The water ends to their mouths and then enters into another river channel, a lake or an ocean. An estuary, another aquatic habitat, is created when freshwater from a river environment mixes with saline water from a marine ecosystem.
A freshwater wetland is a landform saturated with water either seasonally or permanently. Because of its hydric soil, a wide variety of plants and animals thrive in the wetlands. The diverse wildlife found in the wetlands is adapted to thriving in saturated soil conditions. Some examples of wetlands include marshes, mangroves, bogs, swamps and fens.