What are Freshwater Ecosystems

Ecosystem is defined as a system of all living and nonliving objects and their interactions in a specified volume of space. As per the simple definition, an ecosystem contains more than one object and interactions among those objects. In an ecosystem, both non-living and living species are given equal status. Ecosystems are the main sources that control the energy balance of the planet. The structure and the function of an ecosystem are controlled by various factors. Organisms are one key factor that often affects the function and structure of an ecosystem. Their trophic activities such as predation, herbivory, and decomposition, or engineering activities such as shelter construction, burrowing etc. have a major effect on the ecosystem. Similarly, non-living objects always control ecosystems by controlling supplies and movement of water, air, nutrients etc. Moreover, the temperature is another important factor that can control many interactions of an ecosystem.  

Ecosystem Classification

Many ecologists have proposed various classification systems to classify ecosystems. However, there is no such universal classification of ecosystems. Based on the fauna and flora diversity, non-living objects and the structure, we can identify few major ecosystems in the world.

  • Tropical moist forests
  • Temperate forests
  • Arid and semiarid ecosystems
  • Boreal forests
  • Arctic and alpine systems
  • Grasslands, and
  • Aquatic ecosystems

Aquatic ecosystems are again classified into two broad categories; marine and freshwater. Freshwater ecosystems include,

  • Rivers
  • Streams
  • Creeks
  • Springs
  • Ponds
  • Lakes
  • Reservoirs
  • Wetlands

All these freshwater ecosystems mainly contain freshwater in either standing (lentic) or flowing (lotic) condition or in both conditions.

What are Freshwater Ecosystems

Peyto Lake in Banff National Park, Alberta, Canada

What are Freshwater Ecosystems 

Rivers, streams, and creeks are flowing water ecosystems that differ in many aspects such as shape, volume, size, flora and fauna diversity etc.

Rivers are the largest flowing water ecosystems in the planet and carry water for thousands of kilometers. The largest river in the world is the Amazon river in South America, while the second largest river is the Congo river in Africa.

Streams and creeks are smaller flowing water bodies but are still important as they make hydrographic networks of watersheds. These types of ecosystems can be temporary, especially in arid or semi-arid regions due to extremely dry weather conditions during some parts of the year. 

Springs originate from the ground water. Springs have a very narrow water flow with reduced flow rate.

Ponds are small natural water-filled shallow areas with permanent vertical circulation. Water in the ponds can be fresh, saline or brackish. Ponds can be either permanent or temporary bodies of water.  

Lakes are very large water bodies with shallow depths. The water in the lakes can be fresh, saline or brackish. The water quality of lakes depends in the hydrogeological characteristics of their watersheds. Lakes and ponds are classified by their surface area. A pond usually has a surface area of less than 0.1 km2, while a lake has a surface area of more than 0.1 km2. The largest lake in the world is the Caspian Lake, while the second largest lake is the Lake Superior.

What are Freshwater Ecosystems - 1

The three primary zones of a lake

Reservoirs are the man-made lakes with lentic ecosystems. These freshwater systems can be either shallow or deep and are associated with rivers. The largest reservoir in the world is the Volta reservoir in Ghana, while the second largest is Bratsk in Russia.

Wetlands are the areas where the soil is saturated with water. These lands can be extended to hundred of kilometers and can be found with areas of floating or emerged vegetation of aquatic plants. The fauna diversity is often extremely high in wetland ecosystems. Wetlands can be lentic (if associated with a lake) or lotic (if associated with a river). They can be permanently flooded or temporarily dry in certain periods of year.


Freshwater ecosystems are extremely important to maintain the energy balance in the food chain and to carry nutrients from terrestrial ecosystems to marine habitats. Moreover, freshwater ecosystems are known as biological hotspots on the planet Earth due to great flora and fauna diversity.


Sven Erik Jorgensen, Jose Galizia Tundisi and Takako Matsumura Tundisi, Handbook of Inland Aquatic Ecosystem Management (2003), CRC press, NY.

V. Krishnamurthy, Textbook of Biodiversity (2003), Science Publishers Inc, USA.

Image Courtesy:

“Peyto Lake-Banff NP-Canada” By Tobias Alt, Tobi 87 – Own work (GFDL) via Commons Wikimedia

“Primary zones of a lake” By Geoff Ruth – CK12 Earth Science (page 484) (CC BY-SA 3.0) via Commons Wikimedia

About the Author: Yashoda

Yashoda has been a freelance writer in the field of biology for about four years. He is an expert in conducting research related to polymer chemistry and nano-technology. He holds a B.Sc. (Hons) degree in Applied Science and a Master of Science degree in Industrial Chemistry.