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Freshwater and Wetlands Biomes

Explore different freshwater habitats and the ecosystems that thrive there.

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Freshwater and Wetlands Biomes

What may be the most biologically diverse type of ecosystem?

These are wetland marshes in Delaware. Notice the abundance of vegetation mixed with the water. And of course, where there are plants, there are animals. Wetlands are considered the most biologically diverse of all ecosystems. Plant life found in wetlands includes mangrove, water lilies, cattails, black spruce, cypress, and many others. Animal life includes many different amphibians, reptiles, birds, insects, and mammals.

Freshwater Biomes

Freshwater biomes have water that contains little or no salt. They include standing and running freshwater biomes. Standing freshwater biomes include ponds and lakes. Lakes are generally bigger and deeper than ponds. Some of the water in lakes is in the aphotic zone, where there is too little sunlight for photosynthesis. Plankton and plants, such as the duckweed in Figure below, are the primary producers in standing freshwater biomes.

Duckweed and cattails are respectively the primary producers in standing and running freshwater biomes

The pond on the left has a thick mat of duckweed plants. They cover the surface of the water and use sunlight for photosynthesis. The cattails on the right grow along a stream bed. They have tough, slender leaves that can withstand moving water.

Running freshwater biomes include streams and rivers. Rivers are usually larger than streams. Streams may start with runoff or water seeping out of a spring. The water runs downhill and joins other running water to become a stream. A stream may flow into a river that empties into a lake or the ocean. Running water is better able to dissolve oxygen and nutrients than standing water. However, the moving water is a challenge to many living things. Algae and plants, such as the cattails in Figure above, are the primary producers in running water biomes.




A wetland is an area that is saturated with water or covered by water for at least one season of the year. The water may be freshwater or salt water. Wetlands are extremely important biomes for several reasons:

  • They store excess water from floods.
  • They slow down runoff and help prevent erosion.
  • They remove excess nutrients from runoff before it empties into rivers or lakes.
  • They provide a unique habitat that certain communities of plants need to survive.
  • They provide a safe, lush habitat for many species of animals, so they have high biodiversity.



KQED: San Francisco Bay: A Unique Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the ocean. Estuaries can be thought of as the most biologically productive regions on Earth, with very high biodiversity. Estuaries are zones where land and sea come together, and where fresh and salt water meet.

The San Francisco Bay is one of the great estuaries of the world.



  • Freshwater biomes include standing water and running water biomes.
  • Wetlands are extremely important biomes. They may have freshwater or salt water.


  1. Describe a freshwater biome.
  2. Define a wetland.
  3. Why do wetlands have high biodiversity?
  4. A developer wants to extend a golf course into a wetland. Outline environmental arguments you could make against this plan.

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freshwater biome

Aquatic biome in which the water contains little or no salt; may include a pond, lake, stream, or river.


Area that is saturated with water or covered by water for at least one season of the year.

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