Food Web

An expression of the flow of energy through various communities of organisms in ecosystems, typically consisting of four or more trophic levels. Food webs dissipate energy, spreading it out laterally to communities of organisms living at the same trophic level. Most stream and river ecosystems are comprised of food webs, not food chains. For example, sunlight, in-stream macrophytes, macro invertebrates, trout and other insect-eating fishes, predators of trout. Many macro invertebrate and fish species feed on in-stream insects, thus taking away from the flow of energy towards the top trophic levels.

Links
  http://ib.berkeley.edu/labs/power/index.shtml