Bioaccumulation and Biomagnification

Bioaccumulation vs. Biomagnification 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 100 kg 15 50 kg 30 25 kg 45 12.5 kg 60 6.25 kg 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 kg So, 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

Smart Board Diagram Students come up and interact with it

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

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

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 Biomagnification occurs across the food chain Notice how the DDT concentration increases it moves up 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

Focus on the relationship between NRG pyramid and biomagnification.

Biomagnification of Other Pollutants Substance Use and Problems PCB’s insulators in transformers Fire retardant Impairs reproduction Widespread in aquatic systems Heavy Metals Mercury, Copper, Cadmium, Chromium, Lead, Nickel, Zinc, Tin Mercury from gold mining Many from metal processing May affect nervous system May affect reproduction Cyanide Used in leaching of gold Used in fishing Toxic

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."