Question: 156 Which of the following statements is correct?
(1) Presence of large amount of nutrients in water restricts ‘Algal Bloom’
(2) Algal Bloom decreases fish mortality
(3) Eutrophication refers to increase in domestic sewage and waste water in lakes.
(4) Biomagnification refers to increase in concentration of the toxicant at successive trophic levels.
Answer: Option (4)
Explanation:
Biomagnification is the phenomenon in which the concentration of non-biodegradable toxic substances increases progressively at each higher trophic level in a food chain.
As these toxicants move from producers to primary consumers and then to higher consumers,
their concentration becomes maximum at the top trophic level.
Presence of excess nutrients in water promotes algal bloom rather than restricting it.
Algal bloom leads to depletion of dissolved oxygen in water, which increases fish mortality.
Eutrophication refers to nutrient enrichment of water bodies,
not merely the increase in domestic sewage and wastewater.
Therefore, the correct statement is that biomagnification refers to increase in concentration of the toxicant at successive trophic levels.