Knowing Lake Food Chains


Each organism found within the pelagic and benthic zones serves an important ecological role in the complex food chains that support all levels of life found within and around lakes. All organisms in those food chains are influenced by non-living (abiotic) factors and living (biotic) factors in their environment. Abiotic conditions (e.g., temperature, pH, clarity, dissolved oxygen, nutrients, etc.) and biotic conditions (e.g., predation, disease, etc.) of the lake impact organisms in the food chain and help to provide a natural balance to the aquatic ecosystems.

Clearly not all lakes are alike. Some lakes are shallow, warm and contain many species of aquatic algae, fish and other life. Other lakes are deep, with a large volume of cold, well-oxygenated water. These lakes support fewer varieties of plant life and usually provide habitat for trout.
Lakes of all sizes and depths are found across Montana. The biggest threat to these lakes is deteriorating water quality. Once good water quality is lost, it is extremely difficult, if not impossible, and expensive to restore.

Food Chains and Food Webs
Food Chains follow just one path of energy as animals find food.
A Simple Food Chain Example
Phytoplankton are eaten by zooplankton
Zooplankton are eaten by small fish
Small fish are eaten by large fish
Large fish are eaten by osprey

    Typical Lake Food Chain. Diagram courtesy Flathead Lake Biological Station

Food Webs consists of many food chains. They show how plants and animals are connected in many ways to help them all survive.

A Simple Food Web Example
Trees produce nuts which are food for insects and mice
Mice provide food for snakes and coyotes
Nuts and insects are also food for birds and skunks
Skunks and mice provide food for hawks and foxes


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