Food Chains & Food Webs
Plants form the base of Great Lakes food chains. They’re called producers, because they make their own food by converting sunlight through photosynthesis. In the process, they provide food for other organisms.
In the Great Lakes, most producers are phytoplankton (see sidebar), or microscopic floating plants. An example of phytoplankton is green algae. Large rooted plants, another type of producer, provide food and shelter for different organisms, fish and wildlife.
The next level in the food chain is made up of primary consumers, or organisms that eat food produced by other organisms. Examples of primary consumers include zooplankton (see sidebar), ducks, tadpoles, mayfly nymphs and small crustaceans.
Secondary consumers make up the third level of the food chain. Examples of secondary consumers include bluegill, small fish, crayfish and frogs.
Top predators are at the top of the aquatic food chain and include fish such as lake trout, walleye and bass, birds such as herons, gulls and red tailed hawks—and humans!
In reality, many different food chains interact to form complex food webs. This complexity may help to ensure survival in nature. If one organism in a chain becomes scarce, another may be able to assume its role. In general, the diversity of organisms that do similar things provides redundancy, and may allow an ecological community to continue to function in a similar way, even when a formerly dominant species becomes scarce.
However, some changes in one part of the food web may have effects at various trophic levels, or any of the feeding levels that energy passes through as it continues through the ecosystem.