Why Study Food Webs?

The knowledge of how species interrelate is also necessary to understanding how natural and man-made environmental pressures affect ecosystems. These include destructive pollution (toxic chemicals such as PCBs, DDT, mercury, and selenium) which can break or alter the food chain, and nutrient pollution which can shift whole ecosystems toward nutrient-hungry species. An example of the latter is crop fertilizers, sewage, and animal waste escaping into lakes and streams, causing massive algae blooms at the expense of fish and other species.

See some examples of other applications of isotopes to food web studies.
 
 
 

Fig. 2. This diagram shows the relations between typical aquatic organisms. The arrows connect the prey (diet) to the predator (consumer). Several different food webs are shown. View larger image.