Lesson 42 Aquatic Ecosystem: Lakes and Ponds

As geographers study the many ecosystems around the world, many similarities or patterns become evident from one ecosystem to another.

This allows scientists to group ecosystems into categories. Ecosystems can be categorized into two major types: aquatic ecosystems and terrestrial ecosystems.

The key to the meaning of terrestrial ecosystems lies in the word “terrestrial”, which generally means anything occurring on land.

In our last few lessons we learned about terrestrial ecosystems. We learned about the deciduous forest, the tropical rain forest and the temperate grasslands.

Aquatic ecosystems generally refer to interaction of living and non- living entities in the presence of water.

Aquatic ecosystems, or water- based ecosystems, may be fresh water (lakes and ponds) or saltwater (oceans, estuaries and saltwater marshes).

Today we will learn about the freshwater aquatic ecosystem of the lakes and ponds.

Ponds and lakes are found all over the world on every continent of the world.

A lake is a large body of freshwater surrounded by land and a pond is a smaller body of freshwater.

Pond and lake ecosystems do not have a characteristic climate related with them.

For example, a pond in the Amazon in the winter would still be warmer than a pond in the Artic during the summer.

Lake and pond ecosystems are strongly affected by whatever terrestrial ecosystem surrounds them.

People and animals need freshwater to survive. Only 3% of all water on the Earth is freshwater.

Ponds and lakes can range in size from a few yards wide to thousands of miles across.

Ponds and lakes can be divided into 3 zones: the Littoral Zone, the Limnetic Zone and the Profundal Zone.

The Littoral Zone is the part of the lake or the pond that is shallow, usually along the shoreline.

Life is abundant in this zone. The sun shines in, warming the water and feeding the algae and plants.

The algae and plants then provide protective cover and food to insects, crustaceans and animals.

Off shore where the water is deeper the surface area is called the Limnetic Zone.

Here the water is still warmed by the sun supporting tiny slow moving life forms.

There is plant life in the form of phytoplankton and animal life in the form of zooplankton.

Where there is tiny life there is bigger life to eat it, like fish.

Finally, beneath the limnetic zone is the profundal zone, the deep end. Here the water is darker and colder.

The remains of the creatures above settle here after they die. They are consumed by organisms or they decompose.

Since most ponds and lakes are isolated from other bodies of water, the introduction of different species from new locations is non-existent.

There are thousands of organisms associated with lakes and ponds, but for this lesson we will only list some basic typical ones.

These include producers (plant life) like algae, cattails, and lily pads.

One adaptation a plant has to better suit the pond or lake environment is the formation of aerenchyma.

Aerenchyma is tissue with large air spaces in the leaves of the plant making it buoyant. The air pockets in the leaves help the plant to float and get oxygen from the atmosphere directly.

Another adaptation is that many plants have very flexible branches with tapered tips so that in running water, the leaves can be dragged through the water with very little resistance and therefore no tearing.

Animal life includes small organisms such as isopods, arthropods and plankton.

One animal adaptation is that zooplankton and daphnia have become transparent so they can not be seen by predators. This makes it easier for them to survive and reproduce.

Larger organisms are fish, frogs, herons, beavers and turtles.

The producers such as cattails, algae and lily pads get their energy from the sun.

Small organisms such as arthropods and plankton get their energy from these producers.

Larger animals such as beavers and turtles also get their energy from these producers.

Fish get their energy from plankton and isopods and frogs get their energy from insects and arthropods.

The heron gets its energy from frogs, turtles and fish.

The biggest threat today to lakes and ponds is agriculture and industry. Farms and factories use chemicals to help crops grow or factories run. Those chemicals run off into lakes and ponds, disrupting the balance of life.

=tU2F36Y3AdU =tU2F36Y3AdU Let’s watch this video about lakes and ponds

Let’s review what we have learned about lakes and ponds. Answer the attached questions on the worksheet entitled L#42 lakes and ponds.

In our next lesson we will learn about oceans.

Good Job Today! And remember to….

See you next time!