Aquatic ecosystem facts for kids

An estuary mouth and coastal waters, part of an aquatic ecosystem

An aquatic ecosystem is an ecosystem in and surrounding a body of water, in contrast to land-based terrestrial ecosystems. Just like a forest or a desert, an aquatic ecosystem has different parts that all work together.

What makes up an aquatic ecosystem?

Living Things (Biotic Factors)

These are all the plants, animals, and tiny organisms that live in the water. They include:

1. Producers: These are like the chefs of the ecosystem! They make their own food using sunlight through a process called photosynthesis. The most common producers in aquatic ecosystems are algae and aquatic plants like seaweed and water lilies.

2. Consumers: These are the eaters of the ecosystem. They get their energy by eating other organisms. Consumers can be divided into:

• Herbivores: Plant-eaters, like snails that munch on algae or manatees that graze on seagrass.
• Carnivores: Meat-eaters, like sharks that hunt fish or otters that eat crabs.
• Omnivores: These eat both plants and animals, like some turtles or ducks.
• Decomposers: These are the recyclers of the ecosystem. They break down dead plants and animals, returning nutrients to the water. Bacteria and fungi are important decomposers.
• Detritivores: These organisms feed on dead organic matter called detritus. Examples include crabs, worms, and sea cucumbers.

Non-Living Things (Abiotic Factors)

These are the non-living parts of the environment that affect the living things. They include:

• Sunlight: Sunlight is essential for photosynthesis, the process by which plants and algae make their own food. The amount of sunlight that penetrates the water affects which organisms can live there.
• Temperature: Water temperature affects the metabolism of aquatic organisms. Different species have different temperature tolerances.
• Oxygen: Aquatic animals need oxygen to breathe, just like us! Oxygen dissolves in water, and the amount of dissolved oxygen can vary depending on temperature, salinity, and other factors.
• Salinity: This refers to the amount of salt in the water. Aquatic ecosystems can be either freshwater (like rivers and lakes) or saltwater (like oceans and seas).
• Nutrients: Nutrients like nitrogen and phosphorus are essential for plant growth. These nutrients can come from natural sources like decaying organic matter or from human activities like fertilizer runoff.
• Turbidity: This refers to the cloudiness of the water. High turbidity can reduce the amount of sunlight that penetrates the water, affecting photosynthesis.
• pH: This measures how acidic or alkaline the water is. Different organisms have different pH tolerances.

Types

Aquatic ecosystems come in all shapes and sizes! Here are some of the main types:

Freshwater Ecosystems

These ecosystems have very little salt.

• Lakes and ponds: These are bodies of standing freshwater. Lakes are generally larger and deeper than ponds. They can be home to a variety of fish, amphibians, insects, and plants.
• Rivers and streams: These are flowing bodies of freshwater. The current of the water affects which organisms can live there. Rivers and streams can be home to fish, insects, and plants adapted to flowing water.
• Wetlands: These are areas where the soil is saturated with water for at least part of the year. Wetlands can be freshwater, saltwater, or brackish (a mix of fresh and salt water). They are important habitats for many species of birds, amphibians, and reptiles.

Saltwater Ecosystems (Marine Ecosystems)

These ecosystems have a high salt content.

• Oceans: These are the largest aquatic ecosystems on Earth! They cover more than 70% of the planet's surface and are home to an incredible diversity of life, from tiny plankton to giant whales.
• Coral Reefs: These are underwater structures built by tiny animals called corals. Coral reefs are often called the "rainforests of the sea" because they are so diverse and productive.
• Estuaries: These are areas where freshwater rivers meet the saltwater ocean. Estuaries are very productive ecosystems that support a variety of fish, shellfish, and birds.
• Salt marshes: These are coastal wetlands that are flooded by saltwater tides. Salt marshes are important habitats for many species of birds, fish, and shellfish.
• Mangrove forests: These are coastal forests that grow in saltwater. Mangrove trees have special adaptations that allow them to survive in salty conditions. Mangrove forests provide important habitat for many species of fish, birds, and other animals.

Food webs in aquatic ecosystems

Just like on land, aquatic ecosystems have food webs that show how energy flows from one organism to another.

• The Sun: The sun is the ultimate source of energy for most aquatic ecosystems.
• Producers: Algae and aquatic plants use sunlight to make their own food through photosynthesis.
• Consumers: Herbivores eat the producers, carnivores eat the herbivores, and so on.
• Decomposers: Decomposers break down dead organisms and return nutrients to the water, which can then be used by producers.

Why are aquatic ecosystems important?

Aquatic ecosystems perform many important environmental functions. For example, they:

• recycle nutrients
• purify water
• attenuate floods
• recharge ground water
• provide habitats for wildlife
• are used for human recreation, and are very important to the tourism industry

Threats

Unfortunately, aquatic ecosystems are facing many threats from human activities:

• Pollution: Pollution from factories, farms, and cities can contaminate the water and harm aquatic life.
• Overfishing: Overfishing can deplete fish populations and disrupt food webs.
• Habitat destruction: The destruction of wetlands, coral reefs, and other aquatic habitats can lead to the loss of biodiversity.
• Climate change: Climate change is causing ocean acidification, rising sea levels, and changes in water temperature, which can all harm aquatic ecosystems.
• Invasive species: Invasive species can outcompete native species and disrupt food webs.

What can we do to protect aquatic ecosystems?

• Reduce pollution: Reduce your use of pesticides and fertilizers, and dispose of waste properly.
• Conserve water: Use water wisely to reduce the amount of water that is diverted from rivers and streams.
• Support sustainable fishing: Choose seafood that is caught using sustainable fishing practices.
• Reduce your carbon footprint: Take steps to reduce your carbon footprint, such as using public transportation, biking, or walking.
• Educate others: Tell your friends and family about the importance of aquatic ecosystems and what they can do to help protect them.
• Participate in cleanups: Join a local cleanup effort to remove trash and debris from aquatic ecosystems.

See also

In Spanish: Ecosistema acuático para niños

• Aquatic plant
• Hydrobiology
• Hydrosphere
• Limnology
• Ocean