Part 1 Begin by selecting a freshwater or marine aquatic ecosystem as a model for your food web. Be specific. Choose a specific lake. Or, if you choose an ocean ecosystem, identify its geographical area and depth. Keep in mind that deep-sea organisms live in a completely different environment than surface aquatic organisms. Next, conduct research on the following conditions in the ecosystem you chose. They influence the types of organisms that can live there.

geographical features
temperature
depth/light availability
salinity
pH
unique features that contribute to the ecosystem, such as other bodies of water that connect to it, unusual chemistry, and climate
Using the information you gathered, write a paragraph that describes conditions in the ecosystem.
Part 2
Now conduct research on the types of organisms that live in the ecosystem you chose. Note that quaternary consumers and even tertiary consumers can include land animals that rely on the animals in the aquatic ecosystem for food. Collect information based on these guidelines:

Producers: Identify 2-3 species.
Primary (or first-level) consumers: Identify 2-3 species.
Secondary (or second-level) consumers: Identify 2-3 species.
Tertiary (or third-level) consumers: Identify 2-3 species.
Quaternary (or fourth-level) consumers: Identify 1-2 species.
Write down the species you’ve identified for each consumer level in the ecosystem.
part 4 Changes in ecosystems can be attributed to natural causes, such as natural disasters, seasonal variations in climate, currents, and tidal activity. Many of these changes can affect the amount of food resources available in an ecosystem. Research one natural change that currently affects or could affect the aquatic ecosystem you chose. Use your food web model to explain how this change can affect the competition of food resources in your aquatic ecosystem.
part 5 In addition to natural factors, human activity can also alter ecosystems. Conduct research on a human activity that currently affects or can theoretically affect your chosen ecosystem. Use your food web model to explain how this change can affect the competition for food resources.