The definition of freshwater is made on the basis of salt percentage in water. This kind of water contains less than 1% of salts. There are three main types of freshwater biomes i.e. rivers & streams, lakes & ponds, and wetlands. Half of the world's drinking water needs are fulfilled by these sources. About 90% of water needed for bathing is obtained from these freshwater sources. Different life forms supported by this biome include mollusks, insects, around 1200 amphibian species, and 700 species of fish. Useful information about freshwater aquatic biomes and related facts are given below.
Rivers and Streams
The main characteristic of rivers and streams unlike other biomes (wetlands and lakes) is that water is in a flowing state. Rivers have banks at the sides and a bed at the bottom (middle). The water which runs down earth's surface creates streams and eventually, rivers are formed. Owing to high oxygen content in streams and rivers near their source, a variety of fish (trouts and similar others) and other forms of life are found in this area. Catfish are able to survive in waters near the mouth where light doesn't reach to a great depth (in comparison to other zones).
Lakes and Ponds
Area of lakes near the shores is known as littoral zone and is warmer than other zones (limnetic and profundal). The littoral zone being near to the shore, is shallow and receives great amount of sunlight. The plants and fauna which flourish in this area is therefore, varied and includes following organisms: algae, snails, larvae (and eggs of insects), clams, amphibians, and fish. Creatures which feed on the plants and insects mentioned above should include snakes, turtles, ducks, etc.
Limnetic zone is an area just next to the littoral zone. Life in this area can be found in the form of phytoplankton and zooplankton. The planktons are an important link in the food chain that supports most of the food requirements of aquatic species. Profundal zone is the deepest, and the amount of light penetrating this region is the least. The fauna found in this zone primarily include heterotrophs. These creatures feed on the detritus of plants/animals.
Including wetlands in the category of freshwater biomes is a matter of debate. This is because some of the wetlands are those which contain high amount of salt content. The wetlands are characterized by excessive growth of aquatic plants. Micro-environment of wetlands (marshlands) is typically humid and moist; hydrophytes flourish in such areas. The animals found in these marshlands include shellfish and shrimp.
Some Interesting Facts
- Areas which surround the meeting point of rivers and sea water are known as estuaries. These regions exhibit great diversity and variety in terms of flora and fauna owing to high amount of nutrient deposition.
- This biomes account for 20% of the world's total area.
- Precipitation and ice are the important sources of water. These sources help maintain the freshwater ecosystem.
- Few of the plants growing in freshwater possess flat leaves and some of them also have air-filled capsules. These features keep the plants floating on the surface.
- 'Winterkill' is a phenomenon that can be observed in lakes in cold countries. In the winter season, a layer of ice is formed over the surface, which blocks sunlight; it also lowers the level of oxygen. The combined effect of this whole process is that plants and animals get killed to some extent.