Microbes are also important in environmental studies. The breakdown of sewage and oil slicks (spills) returns the environment to its desired original condition. This return to the original environment is called bio-remediation. In the food chains of nature, microbes are often one of the early sources of energy needed to maintain the community. Microscopie algae convert sunlight into useable food and small protozoans and bacteria serve as a primary (bottom) step in food chains. This microscopic plankton is essential ion water communities.