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Biological Characteristics of Lakes

Zones within a lake provide for different varieties of biological lake communities. There are two major water zones discussed here: the littoral zone and the limnetic zone.

The littoral zone is the nearshore area where sunlight penetrates all the way to the bottom of the lake and allows aquatic plants to grow.

The limnetic zone is the open water area where light does not usually penetrate all the way to the bottom. Floating near the surface are microscopic algae called phytoplankton and cyanobacteria. These organisms produce oxygen and are the food for zooplankton. The zooplankton in turn provides food for fish and other aquatic organisms.

These organisms are all part of a food chain or web. A food chain is a linear connection between one organism and another relying on one another to survive. A food web is an interconnected web that illustrates the many connections between organisms.

There are two basic life-sustaining processes in lakes:

• Photosynthesis
• Respiration

The interaction of photosynthesis and respiration by plants, animals, and microorganisms characterize the food web.