Why Study Food Webs?
The study of food webs is critical to understanding the route by which
pollutants get concentrated (bioaccumulated) up the food chain (e.g., in
game fish such as bass). Current examples of bioaccumulation that the USGS
is studying are mercury in the Florida Everglades, selenium in the Central
Valley, and selenium and mercury in San Francisco Bay.
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