Pond Ecosystem

Freshwater pond ecosystem

The freshwater pond ecosystem consists of the areas of the pond bottom, mid-water, pond surface, pond margin, and above the pond system. Let's look into each component and how they are interrelated in the ecosystem.

At the pond bottom, there are low levels of oxygen and light, and as organic matter falls to the bottom of the pond, it is home to decomposers and scavengers.

The mid-water is where the fish and the aquatic insects live, and food is found on both the surface of the pond and the bottom of the pond. Animals living here breathe through their skins and gills. Some examples include the stickleback fish and dragonfly nymphs. On the pond surface, there is a lot of light and oxygen, and the animals found here breathe through lungs, gills, and skin such as ducks, tadpoles, and midge larvae. In the pond margin or the edge of the pond, there is lots of light and oxygen creating a habitat for plants like marsh marigolds to thrive. The plants that grow there provide shelter for insects and small animals, for example, frogs and damselflies. Above the pond system is where birds and insects such as kingfishers, herons, and dragonflies live. They feed in and around the pond.

Nutrient cycling in the freshwater pond ecosystem

Nutrients are vital in ecosystems as they are food that fuels the growth of animals and plants. In the freshwater pond ecosystem, nutrients can be found from three sources.

• One source is the chemicals in the atmosphere that are washed out by rain
• When rocks and minerals are weathered and broken down into the soil, they add nutrients
• Bacteria absorb chemicals from the atmosphere and are stored in the soil.

Nutrients that are found in soil are taken in by producers such as plants for growth. Consumers eat the producers gaining the energy to grow, and when producers and consumers die, they are broken down by decomposers into organic matter and into nutrients.

Pond ecosystem food chain

The balance of the pond ecosystem is regulated by the food chain. The food chain is how each organism gets food and passes on energy and nutrients from one organism to another. It is made up of producers and consumers.

An example of a pond ecosystem food chain would be the first producers, phytoplankton, and aquatic plants like algae that photosynthesis to create glucose from sunlight. Then there are consumers such as small aquatic animals like caddis who would eat producers for their sugars. There are also consumers who would eat other consumers to receive energy for example small fish like a stickleback who eats the caddis and birds like the kingfisher who would eat the fish.

Pond ecosystem food web

The food web of the pond ecosystem shows the relationships between all the producers and consumers.

From the diagram, you can see at least four different food chains. The detritus, algae, and microscopic plants are producers who are at the beginning of the food chains and are eaten by the primary consumers of midge larvae, blackflies, mayflies, and aquatic worms.

The primary consumers are then eaten by the great diving beetle, stonefly, caddis, and dragonfly who are the secondary consumers.

The secondary consumers are eaten by fish who are the tertiary consumers (also fish can be secondary consumers as they feed on mayflies as well.)

Then the tertiary consumers are eaten by quaternary consumers, herons, and kingfishers.

Threats to pond ecosystem

As pond ecosystems are reliant on the balance between biotic and abiotic components, changes to either can threaten the ecosystem. There are both natural and human-made threats to the pond ecosystem.

Natural threats

Lack of rainfall can cause the water levels in a pond to drop. Without water, the pond margins can dry out and the plants die. Less water leads to lower oxygen levels. This can then lead to fewer fish in the pond.

Natural succession can also be a threat to the pond ecosystem. Natural succession is a series of processes of habitats and species changing in an environment. In the case of the pond, over time it is filled up with soil and plant debris which leads to the pond becoming dry land.

Human-made threats

Introducing another species into the pond such as a predatory fish could decrease the number of insects that are usually preyed on by frogs and affect the numbers of the population. Removing another species can be just as destructive as a species reliant on the species for energy could die out without it. Both change the balance of the food web and affect the pond ecosystem.

There have been examples of ponds being drained to make space for farming. This completely destroys the ecosystem. The fertiliser used in farms leeching into the pond can also affect the ecosystem as it can cause algae to thrive and use up the oxygen in the water and the other organisms in the water die of lack of oxygen. Pesticides can also be leaked into the pond to pollute and kill the living organisms in the pond.