Sun

• The sun is the supplier of all life. The beginning of any food chain, it provides the energy needed for basic food sources to grow. In the case of a lake, phytoplankton (composed mainly of algae) is the basic food source. Phytoplankton is a photo-synthesizer, requiring adequate sunlight and temperature to grow.
  
  

Producers

• In the lake ecosystem, phytoplankton is referred to as a producer. Along with sunlight, it requires inorganic ingredients such as phosphorous and nitrogen to prosper. A healthy ecosystem requires just the right amount of phytoplankton at any given time. Too little and there is not enough food to go around. Too much and there is not enough light.
  
  

Primary Consumers

• Primary consumers are zooplankton. Zooplankton are the animal portion of the free-floating, living particles in water. As primary consumers, they eat bacteria, algae, detritus and sometimes other zooplankton.
  
  

Secondary Consumers

• Secondary consumers, such as planktivorous fish or predaceous invertebrates, eat zooplankton. Secondary consumers include benthic (bottom-dwelling) organisms like invertebrates and bottom-feeding fish. Small fish, such as sunfish and perch, eat primarily zooplankton, putting them in this category of feeders as well.
  
  

Tertiary Consumers

• Tertiary consumers include larger fish and other carnivorous animals (loons, grebes, herons, and otters). They prey on small fish. Depending on the size and location of the lake, you find different species.
  
  

Decomposers

• Decomposers, which include bacteria, fungi, and other microorganisms, are the other end of the food chain. They feed on the remains of all aquatic organisms, breaking down or decaying organic matter. Once it has been returned to its inorganic state in this way, it is readily available for new plant growth, and the cycle of life continues.
  
  

Importance

• Our health and many of our activities depend on the health of aquatic ecosystems. If a lake or river system is unhealthy, the water may be unsafe to drink or unsuitable for industry, agriculture, or recreation--even after treatment. This is why humans should try to have as little impact as possible on nature's delicate ecosystems, helping to preserve them at all cost.