question_answer

What is eutrophication? Explain its consequence on the life of plants and animals in such water bodies.

OR

What is biological magnification? How does DDT as a water pollutant undergo biological magnification?

 

Answer:

Eutrophication is excessive growth of algae, plants and animals in water bodies due to the nutrient enrichment, particularly with nitrogen and phosphorus.

Consequences ofeutrophication on the life of plants and animals in such water bodies are as follows:

(a) Presence of large amount of nutrient in such water bodies causes excessive growth of planktonic (free-floating) algae leading to algal bloom. Algal bloom caused deterioration of water quality and fish mortality. Some of them are toxic to human being and animals.

(b) Growth of water hyacinth (aquatic weed) lead to an imbalance in the aquatic ecosystem.

OR

Biological magnification or biomagnification is the increase in concentration of toxic materials like heavy metals and pesticides at each trophic level of a food chain due to their accumulation.

When DDT was used to control mosquitoes in a lake of USA, 800 times more DDT was found in the phytoplanktons than in the water of the lake. Zooplanktons had about 13 times more DDT than phytoplanktons. It was also observed that the fishes population had 9-40 times more DDT than zooplanktons and fish eating birds had 25 times more DDT than fish.