(a) Eutrophication
It is the natural aging of a lake by biological enrichment of its water because of excessive growth of algae, plants, and animals in water bodies due to the nutrient enrichment, particularly with nitrogen and phosphorus. Thus, it is natural and cultural or accelerated. It results in the loss of biodiversity and causes chemical accumulation in the food chain and aging of the water body.
(b) Biological magnification
An increase in the concentration of persistent toxic chemicals at successive trophic levels is called biological magnification or biomagnification. It is because of a toxic substance that gets accumulated by an organism that cannot be metabolized or excreted and is thus passed onto the next trophic level, e.g., DDT.
(c) Groundwater depletion and ways for its replenishment
It is a term that is often defined as long-term water-level declines which are caused by sustained groundwater pumping. Groundwater depletion is experienced by many areas of India. The most severe outcome of excessive groundwater pumping is the water table, which can be lowered in the presence of water. The well has to be deepened, or drill a new well, or at least attempt to lower the pump if groundwater level declines too far. Measures for replenishing groundwater:
(i) Prevent overexploitation of groundwater
(ii) Improvement in water use and reducing water demand
(iii)Rainwater harvesting
(iv)Deforestation can be prevented and plantation of more trees can be initiated.