Interaction among species: Lakes

Lakes are pools of water, where the temperature, oxygen, and light create an environment for organisms to live. They are full of plants, algae, fish, insects, and micro-organisms such as bacteria or fungi. All of these living and non-living things in lakes create an ECOSYSTEM. The living organisms in the lakes share space and resources with others. They often depend on each other and have to interact.

They form a BIOCOENOSIS. Plants and algae produce oxygen and their own food through photosynthesis. Therefore, they are called PRODUCERS. Some algae are so small that they are practically invisible. They float freely in the water.

This is why we call them PHYTOPLANKTON, which means “wandering plants”. Other organisms use oxygen to breathe, and they eat phytoplankton, plants or other animals. They are CONSUMERS. For example, phytoplankton is eaten by tiny crustaceans such as water fleas. These, in turn, become food for fish, such as carp.

Carp can be eaten by a bird like a heron. In this way, organisms are connected in a FOOD CHAIN. Usually, animals eat more than just one kind of food. They belong to different food chains, creating a FOOD WEB. The carp eats phytoplankton, water fleas and insects, so it’s their PREDATOR, but it can be eaten by a heron or a northern pike.

It becomes PREY. This is called PREDATION. There are also organisms such as fungi and bacteria, which eat or decompose dead algae, animals, and plants at all levels of the food chain. We call them DECOMPOSERS. Decomposers break down dead organisms into simple substances such as nutrients.

These are used again by algae to produce food. Organisms which eat the same kind of food, COMPETE with each other. For example, herons compete with other herons to catch carp. They belong to the same species. This is INTRASPECIFIC COMPETITION.

But herons will also compete with pikes, which belong to a different species. Then it’s INTERSPECIFIC COMPETITION. Some organisms form very close relationships. This is called SYMBIOSIS. For example, green algae and aquatic fungi, grow together to form lichen.

Thanks to that, it’s easier for them to survive and they can grow bigger. Both fungi and algae gain something from this relation. It’s a type of symbiosis, called MUTUALISM. A different example of symbiosis is the relationship between pondweed and rainbow smelt fish. The fish finds protection from predators among the pondweed.

The pondweed does not benefit from that but it is not harmed. This kind of symbiosis is called COMMENSALISM. Sometimes one organism benefits and the other one is harmed, and that can also be an example of symbiosis. For instance, Ich parasite attaches itself to a fish and feeds on it. The fish is harmed because the parasite causes a disease.

This is called PARASITISM. Organisms in lakes interact in different ways. They can eat or be eaten by other organisms in a predation relation. They can cooperate forming mutualistic symbiosis, or use other organisms to their own benefit in commensalism or parasitism... Or - like decomposers - they can break down dead organisms and return nutrients back to the environment.

In the end, everything is closely connected within the ecosystem of the lake.