Question

How pesticides, herbicides and fungicides are affecting the ecosystems? Explain about bioaccumulation and biomagnification with examples.

Answer 1

• Biomagnification stands for Biological Magnification, which means the increase of contaminated substances or toxic chemicals that take place in the food chains. These substances often arise from intoxicated or contaminated environments. The contaminants include heavy metals namely mercury, arsenic, pesticides such as DDT, and polychlorinated biphenyls (PCBs) compounds which are then taken up by organisms because of the food they consume. The harmful substances then build up inside the organism’s cells. When organisms in the higher food chain consume the organisms containing the toxins below their trophic levels, the toxins gradually become concentrated in the higher food chain. Because this is a repetitive process in the ecosystem and throughout the entire food chain, the higher organisms are the ones that will accumulate most of the toxins. Agricultural pesticides, fungicides, herbicides, and chemical fertilizers, among other agricultural chemicals, are highly toxic and often find the way into the soils, rivers or lakes and the seas through surface stormwater runoff. It disrupts the interconnected relationships within the food chain. An example of biological magnification and its dangers is any small fish that eats plankton that has been tainted with mercury.
  
• Bioaccumulation is the accumulation of substances, such as pesticides, or other chemicals in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost by catabolism and excretion. An example of bioaccumulation is the use of DDT as an insecticide in the 1950s and 1960s. Birds of prey were badly affected because it made the shells of their eggs very thin, causing them to break easily when the birds tried to incubate them.