Water Biome: Fresh water
A biome is a large area with similar climate and plants. There are a number of biomes on earth, but it is generally agreed that there are seven main biomes.
About three quarters of the earth's surface is covered with water. The water biome is divided into fresh water (water with little or no salt in it in ponds, rivers, streams) and marine, or salt water (ocean).

Ponds and Lakes

©[2008] Jupiterimages Corporation

A pond is a shallow hole where water collects. Plants generally grow around the edges of the pond, and often right across the whole pond. The temperature of the water is similar at the surface and at the bottom of the pond. The bottom is generally covered with mud. There are usually no waves. In places where winters are very cold, the whole pond can freeze solid. Some ponds are seasonal, and only fill at certain times of the year when there is rain.

A lake is bigger than a pond, sometimes thousands of square metres. Plants can only grow along the shoreline because the water is too deep away from the edges. Some lakes are so big that there are waves.

In summer, the temperature of the water in a lake is not the same: the top part of the water gets more of the sun's heat and is warm (about 19-25ºC), the middle layer is cooler because it gets less of the sunlight (aobut 8-19ºC) , and the bottom layer, which does not get any sunlight, is quite cold (about 4-8ºC).

©[2008] Jupiterimages Corporation

'Winterkill' and 'Summerkill' in lakes
More creatures live in the warmer layer of water. Even in the coldest places, most lakes are so big and deep that they don't freeze solid in winter, but a layer of ice can form across the surface. The ice blocks out the sunlight, and oxygen levels in the water drop, killing some plants and animals. This is called 'winterkill'.

algae©[2008] Jupiterimages Corporation

In all freshwater areas around the world, algae (say al-gee) can be found. Algae are not plants, animals or fungi.

There are different kinds of algae, and most are single-celled but some have more than one cell. As they make their food by photosynthesis, algae release oxygen into the water. Photosynthesis uses sunlight as a source of energy to combine carbon dioxide, water and salts to form chlorophyll . This means algae are most abundant in summer.When there is too much algae, the decaying algae reduce the oxygen levels in the water, and this can kill plants and animals. This is called 'summerkill'.


Rivers and Streams
©[2008] Jupiterimages Corporation

Rivers and streams are moving strips of water. The water flows in a channel. The bottom of the channel is called the bed and the sides of the channel are called banks. Rivers are large and flow into the ocean. Rivers and streams make up about 3% of the earth's total fresh water.

Rivers and streams drain the earth of excess water. Water falls from the sky (precipitation) as rain, hail, snow or sleet. Once it reaches the ground, some of the water is absorbed by trees and other plants and the rest filters down into the ground. Most water runs off the surface and eventually joins a creek or stream. Small streams join together to form rivers.

Sometimes small rivers join together to become extremely large rivers. When this happens, the small rivers are called tributaries.

©[2008] Jupiterimages Corporation

A watershed is an area of land where rain water, streams and small rivers all drain into one large area of water such as a large river, lake or ocean. Because ground water also drains from a watershed, all kinds of pollution can find its way to the ocean from many kilometres away. The biggest rivers have the biggest watersheds. Therefore, biomes with lots of consistent rain have more rivers and streams.

Deserts have little rain and fewer rivers. Desert rain is short but very intense, so dry rivers and lakes suddenly become full for a short period of time.

©[2008] Jupiterimages Corporation

The mouth of a river is where it meets the ocean.

Rivers carry soil along as they move, and this is dropped at the mouth of the river as it enters the ocean, and gradually builds up, making new land. This is called a delta. Rivers tend to branch off in many directions through the delta, creating many islands.

A river delta

Rivers that are permanently frozen are called glaciers. Glaciers are found in places such as Antarctica, the frozen continent where the South Pole is located, but glaciars are also found in countries where there are very high mountains. Even though they are frozen, glaciers are indeed rivers and do move very slowly down the mountain to the sea.

Click here to find out about Rivers of the World

 

Wetlands



Find out about other biomes:
Rainforest
Desert
Tundra
Taiga
Deciduous forest
Grassland
Biomes main page

If you use any part of this in your work, acknowledge it in your bibliography like this:
Sydenham, S. & Thomas, R. Water Biome : Fresh Water . [Online] www.kidcyber.com.au (2002)

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