Summary
Persistent toxins like DDT become more concentrated at each higher trophic level.
In depth
Persistent, fat-soluble chemicals (DDT, mercury, PCBs) are not metabolised or excreted and accumulate in tissues. Concentration rises up the food chain: DDT thinned the eggshells of birds of prey and caused declines in eagles and peregrines.
Rachel Carson's Silent Spring (1962) drew attention to it.
It requires persistence, fat solubility and slow excretion. Bioaccumulation is build-up within an organism; biomagnification is increase along food chains.
Example: PCBs concentrate in orcas and polar bears.
Examples include DDT, which thinned eggshells in birds such as peregrine falcons, brown pelicans and bald eagles; Rachel Carson's Silent Spring (1962) raised awareness, and DDT agricultural use was banned in the USA in 1972, after which populations recovered. Methyl mercury, produced by bacteria in sediments, magnifies in fish, and caused Minamata disease in Japan from industrial discharge in the 1950s.
Bioaccumulation (build-up in an organism over time) differs from biomagnification (increase up the chain). Persistent organic pollutants travel long distances; Arctic marine mammals and Inuit people carry high PCB levels. The Stockholm Convention bans many such chemicals.
Example: DDT concentration can rise from 0.000003 ppm in water to 25 ppm in fish-eating birds, about a ten-million-fold magnification.
Frequently asked questions
What is Biomagnification?
Persistent toxins like DDT become more concentrated at each higher trophic level.
Which area of biology covers Biomagnification, and how advanced is it?
Biomagnification is one of the 54 topics in Ecology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Eutrophication, Trophic Levels, Trophic Cascade.
Can you give an example of Biomagnification?
Tuna and swordfish carry mercury and are limited in pregnant diets.
What should I learn before Biomagnification?
Work through the Beginner topics in Ecology first, such as Ecology, Ecosystem, Biotic and Abiotic Factors, then return to Biomagnification. Intermediate topics assume the Beginner vocabulary.
What topics are related to Biomagnification?
The closest topics to Biomagnification are Eutrophication, Trophic Levels, Trophic Cascade, Microbial Ecology. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Biomagnification?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Biomagnification. To practise the whole of Ecology, use the Ecology quiz.
How is Biomagnification different from Eutrophication?
Biomagnification: Persistent toxins like DDT become more concentrated at each higher trophic level. Eutrophication: Nutrient enrichment of water bodies causing algal blooms, oxygen depletion and fish kills. Read both side by side and note what each one explains.
How should I study Biomagnification step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Eutrophication and explain the difference aloud. Finally, take the Ecology quiz and come back to this page for any question you miss.