Bioaccumulation in relation to food webs

Food chains show how energy is transferred through a series of living things, by the process of eating and being eaten. A food web is made up of several food chains. Living things that can use the energy of the sun and non-living things (inorganic material such as air, water, and dirt) to produce food (organic material) are called producers. In the sea, these include seaweeds and phytoplankton.

Living things that consume other living things for food are called consumers. Consumers that eat producers are called herbivores. Consumers that eat herbivores are called carnivores. Each of these steps is called a trophic level. As most animals eat more than one kind of thing, food webs can get quite complex, with each trophic level relying on the level below for sustenance. This complexity is what makes the tremendous diversity of life in the oceans possible. Changes at one trophic level, such as an increase in population, affects other trophic levels. No matter where living things might be on the chain, when they die, they end up being consumed by decomposers that convert the organic materials into simpler inorganic nutrients that can be used by producers.

Bioaccumulation

Roughly bioaccumulation means "you are what you eat."

All living things accumulate chemicals in their bodies through the air they breathe, food they eat or the water they drink or live in. Chemicals that are not used up or excreted can become concentrated in the body as one animal eats another in the food chain.

Marine mammals accumulate and store chemical pollutants in their fat. Many marine mammals eat other aquatic animals that have consumed pollutants. The toxins that their prey have consumed are accumulated by the mammalian predators and deposited in their fat.

Marine mammal mothers then pass these toxins on to their suckling offspring through their milk, which has high concentrations of fat. This is a serious problem found in the beluga whale populations of the St. Lawrence, and is also found in other whale populations throughout the world.

Goksenin Sen
Marine Educator


Reference:
Untangling Food Webs and Bioaccumulation. In Secrets at Sea. Retrieved from http://www.secretsatsea.org/story/2a.html in June, 2012.
Photo credits: European Commission Glossary. Retrieved from http://ec.europa.eu/health/opinions/en/dental-amalgam/glossary/abc/bioaccumulation-bioaccumulate.htm