Aquatic Habitats

An aquatic habitat is a habitat with water. It includes areas that are permanently covered by water and surrounding areas that are occasionally covered by water.

Estuaries, rivers, and marshes are examples of aquatic habitats.

The water in the estuary contains small pieces of plants, detritus (waste or debris of any kind), microscopic organisms, and algae in the water. Water is more salty closer to the sea, less salty as you move up the river. Salt in the water makes the water heavier than freshwater. This is why it is easier to float in ocean water than a lake. At the bottom of an estuary, the soil or mud is thick and deep. Small organisms live and breathe in the top layers of mud, which contains some oxygen. Many plants live in different parts of the estuary. Some plants grow in marshes, their roots grow in the mud, and the stem submerged when the tide comes in.

Some plants and animals live completely underwater, such as the sea lettuce. Then there are plants and animals that float and drift in the water, such as phytoplankton and zooplankton. There are animals that live underwater, in the top layer of mud, such a oysters. There are some free-swimming, such as the striped bass.

Notes on Surface and Ground Water


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Natural events affect aquatic environments.

Climate, weather, temperature change, drought and flooding are natural factors that affect estuaries and rivers.

Tides affect salinity (amount of salt ). Rising levels of ocean water at the shore pushes more saltwater up into the estuary and river. During low tide, ocean water draws back from the estuary.

Flooding causes the estuary to get more freshwater from the river. When a river floods it deposits nutrient rich sediment on the banks, bits of vegetation washes into the water and become food for aquatic organisms. Floods replenish lakes and ponds, it raises the water table.

Flood through extreme events can be detrimental to aquatic system until balance is reached.


Human Activities affect aquatic environments.

Human activities affect aquatic environment in the most disruptive way.

Humans affect aquatic habitats in activities such as oil sands, aggregate mining, forestry, wildlife hunting and tourism.

These activities affect the water cycle, interferes with the level of streams and flow of water, drain wetlands, and eliminate aquatic organisms. Some of these activities uses a lot of our water resources such as oil sands and mining.

Picture 1: Water pouring from a drain pipe to the river, polluting the environment. 2: Fossil fuel is burned and sulfur dioxide and nitrous oxide gases are release into the air. 3. These gases dissolve in raindrops that fall to earth as acid rain. It destroys plant and 4. flows into streams and lakes. Many species are unable to survive in this type of aquatic habitat.

When people build dams, they change freshwater ecosystems from a flowing system into a still system.

Dams can disrupt the reproductive cycles of organism. It causes water temperatures to be warm or cold. This confuses organism whose growth and reproduction is triggered by temperature changes. Many fish leave large lakes and oceans and swim up stream to lay their egg. Dams can keep these fish from reaching their spawning grounds.

All life is made of water and needs water. Water is our most threaten resource. The decreasing amounts and polluted, unsafe water is leading to sickness and death. This is the most important reason we should protect our aquatic habitats and all habitats.

Learn more of this under the topic of ecosystems and cycles.


Make a list of things that live in estuaries and rivers. Discuss how a few of these things would fare if the water they live in was saltier, or if there was a flood. Go to the CHAT. Click on the link below.

Essay: Write a short paragraph explaining why you think it is important to save Earth’s Coral reefs.