Write critical notes on the following:

(a) Eutrophication

(b) Biological magnification

(c) Groundwater depletion and ways for itsreplenishment

(a) Eutrophication:- It is the natural ageingprocess of a lake caused due to nutrient enrichment. It is broughtdown by the runoff of nutrients such as animal wastes, fertilizers,and sewage from land which leads to an increased fertility of thelake. As a result, it causes a tremendous increase in the primaryproductivity of the ecosystem. This leads to an increased growth ofalgae, resulting into algal blooms. Later, the decomposition of thesealgae depletes the supply of oxygen, leading to the death of otheraquatic animal life.

(b) Biological magnification: - To protectthe crops from the several diseases and pests, a large number ofpesticides are used. These pesticides reach the soil and are absorbedby plants with water and minerals from the soil. Due to rain, thesechemicals can also enter water sources and into the body of aquaticplants and animals. As a result, chemicals enter the food chain.Since these chemicals cannot be decomposed, they keep on accumulatingat each trophic level. The maximum concentration is accumulated atthe top carnivore’s level. This increase in the concentrationof pollutants or harmful chemicals with an increase in the trophiclevel is called biological magnification. For example, high DDTconcentrations were found in a pond. The producers (phytoplankton)were found to have 0.04 ppm concentration of DDT. Since many types ofphytoplankton were eaten by zooplankton (consumers), theconcentration of DDT in the bodies of zooplankton was found to be0.23 ppm. Small fish that feed on zooplankton accumulate more DDT intheir body. Thus, large fish (top carnivore) that feed on severalsmall fish have the highest concentration of DDT.

(c) Ground water depletion and ways for itsreplenishment: - The level of ground water has decreased in therecent years. The source of water supply is rapidly diminishing eachyear because of an increase in the population and water pollution. Tomeet the demand of water, water is withdrawn from water bodies suchas ponds, rivers etc. As a result, the source of ground water isdepleting. This is because the amount of groundwater being drawn forhuman use is more than the amount replaced by rainfall. Lack ofvegetation cover also results in very small amounts of water seepingthrough the ground. An increase in water pollution is another factorthat has reduced the availability of ground water.

Measures for replenishing ground water:-

(i) Preventing over-exploitation of groundwater

(ii) Optimizing water use and reducing waterdemand

(iii) Rain water harvesting

(iv) Preventing deforestation and plantationof more trees