Bioaccumulation and Biomagnification

Bioaccumulation vs. Biomagnification

Bioaccumulation: The increase in concentration of a substance

greater than the outside environment Biomagnification:

The increase in concentration of a substance as it moves through a food chain

Pro: vital nutrients such as vitamins, minerals, essential fats and amino acids

Con: pollutants, metals, pesticides

For Bioaccumulation to occur The chemical must be:

Long lived – the chemical persists in the environment for long time before breaking down.

Mobile – if it will stay in one place, it is unlikely to be taken up by organisms

Fat soluble – if it soluble in water, it will be excreted by the organism

Biologically active – if it is not active biologically, it may biomagnify, but it won’t cause any problems

A Classic Example: DDT DDT – dichloro-dipheny-trichloroethane

(chlorinated hydrocarbon) It has a half-life of 15 years – that means if

100 kg of DDT is used it will break down as follows:

Year Amount Remaining

0 100 kg

15 50 kg

30 25 kg

45 12.5 kg

60 6.25 kg

75 3.13 kg

90 1.56 kg

105 0.78 kg

120 0.39 kgSo, after 100 years, there will still be about a kg of DDT in the environment!

DDT (cont’d) DDT – not very toxic for humans But

highly toxic to insects In high concentrations it can cause problems in other

animals shell-thinning and feminization in birds

Here is an ecosystem, that has been exposed to DDT.

Notice how the lowest organism on the food chain has 1 part per million DDT

Since the next organism (beetle) will eat several water boatmen, it will accumulate greater concentrations of DDT

Bioaccumulation

As the DDT moves up the food chain – there is a greater conc. 2 ppm

ppm = parts per million

3 ppm

4 ppm

7 ppm

17 ppm

Bioaccumulation occurs in each organism since the DDT is in > conc. than in the environment

17 ppm

Notice how the DDT concentration increases it moves up the Food chain

Biomagnification occurs across the food chain

• The next slide takes the information from the previous slide and shows it in a trophic level diagram

• Focus on the relationship between NRG pyramid and biomagnification.

• Notice how as we move up the pyramid, DDT conc increase and NRG decreases.

Biomagnification of DDT

Biomagnification of Other Pollutants

Substance Use and Problems

PCB’s insulators in transformersFire retardantImpairs reproductionWidespread in aquatic systems

Heavy MetalsMercury, Copper, Cadmium, Chromium, Lead, Nickel, Zinc, Tin

Mercury from gold miningMany from metal processingMay affect nervous systemMay affect reproduction

Cyanide Used in leaching of goldUsed in fishingToxic

Biomagnification of Mercury

Look at the terminology.

Notice the reference to parts per million or parts per trillion.

This is a common language used to represent concentration of pollutants.

Internet Video Link Biocourse Bioaccumulation Link

Summary Bioaccumulation and biomagnification are

natural processes Important for uptake of essential nutrients Can also lead to build up of harmful chemicals. In order to avoid biomagnification of undesirable

substances, these substances should be immobile, water soluble, short-lived, and biologically inactive

Rachel Carson "Man's attitude toward nature is today critically

important simply because we have now acquired a fateful power to alter and destroy nature. But man is a part of nature, and his war against nature is inevitably a war against himself…[We are] challenged as mankind has never been challenged before to prove our maturity and our mastery, not of nature, but of ourselves."