Write critical notes on the following :
(a) Eutrophication .
(b) Biological magnification .
(c) Groundwater depletion and ways for its replenishment .

Explanation

a. Domestic sewage and fertillizers add large quantities of nutrients such as nitrates and phosphate to the fresh water ecosystem . The rich supply of these nutrients make blue green algae, green alage and other planktons to grow abundantly . This increased productivity of water bodies brought about by nutrient enrichment is known as equatrophication.
(b) Some chemicals used in biocides are not degradable or degraded very slowly in nature . The long range effects of such chemicals are in fact a threat to our ecological security. Indiscriminate used of such chemicals could make them an intergral part of our biological , geological and chemicals could be metablosied or excreted out. These pollutants get deposited in fat contaning tissue . For instance, if a non -degradable pollutant DDT enters a pond , it is taken as such by the plants , then reaches to zoo plankton , the to fishes and finally in the body of brids who eat the fish. More threatening factor is the DDT concentration continuously increases in successive trophic levels in a food chain . This phenomenon is called bioloigcal amphification or biological magnification.
c . Due to overpopulation and urbanisation the level of groundwater is decreasing. This depletion can be replenished by harvesting rain water , protecting natural water bodies, subtainable use of water , etc .