Aquatic plants provide shelter and food for a variety of fish and insect larvae.  Bacteria, worms, crustacean and insect larvae live in the stream bed. Frogs, turtles and salamanders live in freshwater streams during some part of their lives. All these organisms are part of food chains and food webs.

Energy is passed from one living thing to another through food chains.  Plants, the primary producers in a food chain, capture energy directly from the sun through a process called photosynthesis.  All food chains start with plants. In a stream, algae, other living plants, dead leaves and plant debris that fall into the stream serve as food for aquatic organisms. The energy from plants will eventually pass through several different living organisms. 

Insects, amphibians, crustaceans and some larval stages of fish eat plant material in the streams.  Plant-eating animals, or herbivores, gain some of the energy stored in the plant material they eat.  Other organisms, such as adult fish, birds and mammals eat herbivores and again, energy is passed up the food chain. 

Food chains are relatively short.  Many food chains consist of one plant connecting with three or four species of animal.  Food chains are short because energy isn’t transferred very efficiently up the food chain.

Food webs are more complex than food chains.  While each species may have a unique food chain, there may be a point in the chain where several species depend upon the same food source.   As a result, these food chains interlink to form a food web.

Example of an aquatic food web.