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Wiki Education Foundation-supported course assignment[edit]

This article was the subject of a Wiki Education Foundation-supported course assignment, between 1 September 2020 and 20 December 2020. Further details are available on the course page. Student editor(s): Tpc1999, Jmb15006. Peer reviewers: RenLK.

Above undated message substituted from assignment by PrimeBOT (talk) 15:47, 16 January 2022 (UTC)Reply[reply]


Bioaccumulation & Biomagnification 04/03/02

Based on Mader, Sylvia S. 1996. Biology - 5th Ed. WCB and Cox, G.W. 1997. Conservation Biology - 2nd ed. WCB

In this section, we will examine how pollutants move through the various trophic levels in an ecosystem. To understand this material, you have to understand trophic levels, food chains, and food webs, as well as pyramids of biomass. If you haven't reviewed basic ecology yet; perhaps you better do so now: Review Basic Ecology

There are two basic terms we are discussing here. Bioaccumulation refers to how pollutants enter a food chain; biomagnification refers to the tendency of pollutants to concentrate as they move from one trophic level to the next. Here are some definitions of these terms: oneday i will be rich and famous T.M. Bioaccumulation: increase in concentration of a pollutant from the environment to the first organism in a food chain Biomagnification: increase in concentratore it can become dangerous. If it is not mobile, it will stay in one place and is unlikely to be taken up by organisms. If the pollutant is soluble in water it will be excreted by the organism. Pollutants that dissolve in fats, however, may be retained for a long time. It is traditional to measure the amount of pollutants in fatty tissues of organisms such as fish. In mammals, we often test the milk produced by females, since the milk has a lot of fat in it and because the very young are often more susceptible to damage from toxins (poisons). If a pollutant is not active biologically, it may biomagnify, but we really don't worry about it much, since it probably won't cause any problems.

Classic example: DDT DDT stands for dichloro, diphenyl trichloroethane. It is a chlorinated hydrocarbon, a class of chemicals which often fit the characteristics necessary for biomagnification. DDT has a half-life of 15 years, which means if you use 100 kg of DDT, it will break down as follows:


Amount Remaining 


100 kg 


50 kg 


25 kg 


12.5 kg 


6.25 kg 


3.13 kg 


1.56 kg 


0.78 kg 


0.39 kg 

This means that after 100 years, there will still be over a pound of DDT in the environment. If it does bioaccumulate and biomagnify, much of the DDT will be in the bodies of organisms. DDT actually has rather low toxicity to humans (but high toxicity to insects, hence its use as an insecticide). Because it could be safely handled by humans, it was extensively used shortly after its discovery just before WW II. During the war, it was used to reduce mosquito populations and thus control malaria in areas where US troops were fighting (particularly in the tropics). It was also used on civilian populations in Europe, to prevent the spread of lice and the diseases they carried. Refugee populations and those living in destroyed cities would have otherwise faced epidemics of louse-born diseases. After the war, DDT became popular not only to protect humans from insect-borne diseases, but to protect crops as well. As the first of the modern pesticides, it was overused, and soon led to the discovery of the phenomena of insect resistance to pesticides, bioaccumulation, and biomagnification.

By the 1960's, global problems with DDT and other pesticides were becoming so pervasive that they began to attract much attention. Credit for sounding the warning about DDT and biomagnification usually goes to the scientist Rachel Carson, who wrote the influential book Silent Spring (1962). The silent spring alluded to in the title describes a world in which all the songbirds have been poisoned. Her book of course was attacked by many with vested interests.

I recently came across an essay from Jonathan Tolman at the Competitive Enterprises Institute which completely misses the main point we get from Silent Spring. I guess the fact that people are still scared of the book 35 years later says something about its message. Sure, scientific discoveries have shown weaknesses in some of Carson's positions, but the basic message that indiscriminate use of pesticides will have lasting and detrimental effects remains strong. The author's point in the CEI essay seems to be that if nature makes dangerous chemicals, why should we be concerned when humans make more dangerous chemicals and in huge quantities, then spread them around out of airplanes so everyone gets a dose? It's amazing what people will say to make a buck. I note that his on-line resume lists a bachelor's degree in Political Science, presumably that degree qualified him for work as an environmental and chemical analyst. Anyway, back to science:

Case study: Long Island Estuary (Figure 22.1 in Cox) In your textbook, Cox reports on a study done in 1967 on Long Island Sound. The levels of DDT in tissues of various animals in the sound showed bioaccumulation factors of 800x, and biomagnification factors up to 31 times. When we look at the whole food chain, the overall magnification is over 200,000x!

water to zooplankton:


zooplankton to fish #1: 31x fish #1 to fish #2: 1.7x fish #2 to gull: 4.8x overall: 202,368x

While DDT isn't particularly lethal (except to insects, and we need many of them around), it has a number of sub-lethal effects. Most prominent is the phenomenon of shell-thinning in birds, particularly carnivorous birds (raptors) - birds that eat other birds, birds that eat carrion (dead animals), and birds that eat fish. Ospreys are one of the raptors that have been adversely affected, as have bald eagles. Other fish-eating water birds have been affected as well. Because of the DDT, the shells are too thin to brood. Many populations have recovered following the banning of DDT in the US, but migratory birds may be exposed to pesticides in other countries. Recently, some studies have shown effects on sex ratios in some species of birds, with the males becoming "feminized", presumably the result of compounds in the environment mimicing the female hormone estrogen.

Heavy metals and other substances DDT is not the only toxin to biomagnify. All of the following have the potential to biomagnify:


Use & Problems 

PCB's polychlorinated biphenyls insulators in transformers plasticizer fire retardant biomagnifies impairs reproduction widespread in aquatic systems

as airborne contaminants 

in sediments in the Mississippi River

PAH's polynuclear aromatic hydrocarbons component of petroleum products carcinogenic

Heavy metals: mercury copper cadmium chromium lead nickel zinc tin (TBT or tributyltin)

mercury from gold mining 

many from metal processing may affect nervous system may affect reproduction

from an interesting student project 

heavy metals in the Mississippi River - great source!

cyanide used in leaching gold used in fishing toxic

effects on coral reefs 

health information proposed gold mine and its effects report of a spill of cyanide

selenium concentrated by farming desert soils reproductive failures toxic

selenium at a wildlife refuge in Wyoming 


Modern pesticides, such as carbamates and organophosphates, are "safer" in that they are not persistent, one of the requirements for biomagnification. They are, however, more toxic, and insects are developing resistance to them. It must be remembered that we use pesticides for more that making pretty produce. Pesticides are sometimes necessary to protect a basic food supply and to protect human health. The concept of integrated pest management, or IPM, has been developed to improve control of pests while decreasing the need for pesticides. IPM uses a variety of methods to control pests. These include biological controls, and cultural practices such as timing planting and harvest to avoid periods of peak activity by pest species, and scouting to determine how big a problem the pests are actually causing (rather than just spraying to prevent a problem that may never arise). Economics are watched closely; pesticides are never used if the cost of the pesticide would exceed the cost of the crops being saved (you'd be amazed at how often people have spent more on pesticides than the crop was worth). IPM relies heavily on information, and the internet is being used extensively.

Other pollutants: Other pollutants of importance are plastics, radioisotopes (which may be both toxic and radioactive!) and oil. Plastics are eaten by many organisms and can cause mechanical injury, strangulation, or starvation. Radioisotopes can damage biological molecules, particularly DNA, leading to cancer, other illnesses, or death. Oil smothers aquatic organisms, cutting them off from oxygen. It can also infiltrate the insulating feathers of seabirds (or fur of sea-going mammals) and cause them to die from hypothermia (or cause them to sink). Oil spills are a serious problem in marine environments.

Regulations: Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) 1972 requires registration of pesticides for specific uses London Dumping Convention 1972 ratified by 64 countries bans deliberate discharge of various toxic or other wastes International Convention for the Prevention of Pollution from Ships (MARPOL) 1988 prohibits dumping of plastics at sea ratified by 40 countries More Federal Acts

Environmental Biology Top Page About Sequences About Ecosystems

Biomagnification of radioactives[edit]

This possibility should be included in the article if a meltdown occurs at the Japanese nuclear power facilities at Fukushima located next to the ocean, the pollution could reach alaskan fishing waters due to the ocean currents flowing in a circular pattern. Far ranging fish such as salmon may also be afflicted.AnimeJanai (talk) 14:21, 15 March 2011 (UTC)Reply[reply]

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Hi (talk) 13:45, 8 December 2021 (UTC)Reply[reply]


1) Bioaccumulation 2) Biomagnification Bioaccumulation • Bioaccumulation is the gradual accumulation of pollutants, chemicals (chronic poisoning) or other substances in an organism. • Bioaccumulation occurs when the rate of loss of the substance from the body of the organism through catabolism (breakdown of complex molecules in living organisms), or excretion is lower than the rate of accumulation of the substance. • As persistent organic pollutants like DDT are long-lasting, the risk of bioaccumulation is high even if the envi- ronmental levels of the pollutant are not high.

Biomagnification:- • Biomagnification refers to progressive bioaccumulation (increase in concentration) at each tropical level with the passage of time. • In order for biomagnification to occur, the pollutant must have: 1. a long biological half-life (long-lived), 2. must not be soluble in water but must be soluble in fats. E.g., DDT. • If the pollutant is soluble in water, it will be excreted by the organism. • Pollutants that dissolve in fats are retained for a long time. • Hence it is traditional to measure the amount of pollutants in fatty tissues of organisms such as fish. • In mammals, milk produced by females is tested for pollutants since the milk has a lot of fat in. Biomagnification of DDT in an Aquatic Food Chain (talk) 02:44, 18 July 2022 (UTC)Reply[reply]

Wiki Education assignment: ENGW3307 Adv Writing for the Sciences 14214[edit]

This article was the subject of a Wiki Education Foundation-supported course assignment, between 7 September 2022 and 14 December 2022. Further details are available on the course page. Student editor(s): Sterna25 (article contribs).

— Assignment last updated by Sterna25 (talk) 16:20, 18 November 2022 (UTC)Reply[reply]

Edit Plan[edit]

Hi! Here are some of the things I'm planning to improve with this article:

- substances that biomagnify has no inline citations, add those or fix in another way

- deal with pop-up at top of the page, make sure there are enough in-line citations

- A lot of the current sources are 15-30 years old- I want to look at current literature and see if anything has changed since then Sterna25 (talk) 15:28, 22 November 2022 (UTC)Reply[reply]

more precise terminology regarding biomagnification and nouns toxic and toxin[edit]

I have revised the terminology to make it more precise. As well explained in Toxin toxicologists use the word toxin to refer to toxicants of biological origin, but in lay usage the nouns toxin and even toxic are used to refer to harmful substances of artificial origin. Moreover, biomagnification, and its opposite biodilution, are natural processes which can occur for any substance, not only artificial or harmful ones. CharlesHBennett (talk) 14:12, 21 January 2023 (UTC)Reply[reply]

Old Wives Tail[edit]

"A well known example of the harmful effects of DDT biomagnification is the significant decline in North American populations of predatory birds such as bald eagles and peregrine falcons due to DDT caused eggshell thinning in the 1950s."

Does anyone actually still believe this is true?!?! (talk) 19:38, 25 August 2023 (UTC)Reply[reply]