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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.

See Biomes: Wetlands at http://www.youtube.com/watch?v=1lLtfbde16A and Biomes: Freshwater at http://www.youtube.com/watch?v=tU2F36Y3AdU for additional information.

KQED: Restoring Wetlands

More than 100,000 acres of wetlands are being restored in the Northern California Bay Area, but how exactly do we know what to restore them to? Historical ecologists are recreating San Francisco Bay wetlands that existed decades ago. To learn more, see http://science.kqed.org/quest/video/wetlands-time-machine/.

For more than 100 years, south San Francisco Bay has been a center for industrial salt production. Now federal and state biologists are working to restore the ponds to healthy wetlands for fish and other wildlife. Salt marshes are rich habitats that provide shelter and food for many species, some of which are endangered or threatened. See http://www.kqed.org/quest/television/from-salt-ponds-to-wetlands for additional information.

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. See http://www.youtube.com/watch?v=clZz2OjE5n0 for further information.

Engineering River Cleanups

Contaminants released decades ago are still affecting our environment. This is particularly evident in the sediment on the floors of rivers, streams, lakes and oceans. The released toxins are absorbed by fish, affecting the ecological food chain as well as the fish we eat. Can this issue be lessened? See Engineering River Cleanups at http://youtu.be/oiHNdcdU1pM?list=PLzMhsCgGKd1hoofiKuifwy6qRXZs7NG6a for additional information.


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

Explore More

Use this resource to answer the questions that follow.

  • http://www.hippocampus.org/Biology\begin{align*}\rightarrow\end{align*} Non-Majors Biology \begin{align*}\rightarrow\end{align*} Search: Freshwater Biomes
  1. Why are freshwater biomes considered "limited"?
  2. Describe a wetland. Give examples of wetlands.
  3. What are the 3 zones of ponds and lakes?
  4. Compare the littoral zone to the profundal zone.
  5. What types of organisms can thrive in the headwaters of streams and rivers?


  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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