Mon March 14, 2011 By: Theodosia Lourdes Thomas

If the concentration of DDT were 0.2 ppm in water of a lake, what would be its likely concentration in fish in the following food chain? Plankton -> Fish -> Fish-eating birds. Sir/Mam please explain how to calculate.

Expert Reply
Mon March 14, 2011
Dear Student,
Organisms higher in the food chain consume DDT every time they feed on organisms lower down in the food chain, if they are contaminated with DDT.

The biomass at each level in a food chain gets less, so the concentration of DDT will increase.

The increase in concentration of pesticides in a food chain is called bio-magnification.

DDT concentration:

Producer (Plankton 0.2ppm)--------- Primary consumer ( Fish1.0ppm)-------- secondary consumer(Fish eating birds.5.0ppm)

Based on the above explanation, we can say that DDT becomes concentrated in the tissues of organisms of three successive trophic levels in a food chain.The process of concentration goes right on up the food chain from one trophic level to the next.
We hope that clarifies your query.




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