Solution:

(a) Eutrophication –

It is the natural aging process of a lake induced by nutrient enrichment caused by the influx of nutrients such as fertilizers, animal wastes, and sewage from land, resulting in enhanced lake fertility. As a result, the ecosystem’s primary production has skyrocketed, resulting in increased algae growth and, algal blooms. The degradation of these algae limits oxygen supply over time, causing aquatic animal life to perish.

(b) Biological magnification

Pesticides are widely employed to protect crops from a variety of illnesses and pests. These pesticides are absorbed by plant components together with minerals and water from the soil when they enter the soil. As a result of rain, these chemicals can infiltrate water sources, as well as the bodies of aquatic animals and plants, and hence into the food chain. Since these compounds cannot be dissolved, they accumulate at all trophic levels, with the majority of the accumulation occurring at the level of the top carnivore. This is known as biological magnification, and it occurs when the concentration of dangerous contaminants increases as the tropic level rises. A pond, for example, was developed with high DDT concentrations. DDT levels in the producers (phytoplankton) are 0.04 ppm. The concentration of DDT in the bodies of zooplankton was found to be 0.23 ppm because this phytoplankton was absorbed by the consumers, zooplankton. When this is swallowed by small fish, more DDT is accumulated in their bodies. As a result, large fish (top carnivores) preying on various little fish had the highest levels of DDT.

(c) Groundwater depletion and ways for its replenishment

The level of groundwater has dropped in recent years. Water availability from sources is fast dwindling with each passing year as a result of rising water pollution and population growth. Water is being removed from water bodies such as rivers and ponds to supply the need for water. As a result, the groundwater supply is rapidly diminishing, as the amount of groundwater removed for human consumption exceeds the amount restored by rainfall. Due to the lack of vegetative cover, very small amounts of water enter the ground. A rise in water contamination has also contributed to a decrease in groundwater supply.

Measures to replenish groundwater are as follows:

(i) Over-exploitation of groundwater must be prevented

(ii) Water use must be optimized and water demand must be reduced

(iii) Promote and encourage rainwater harvesting

(iv) Prevent deforestation

(v) Promote afforestation, plant more trees