Question: 129 Which one of the following statements is NOT correct?
(1) Water hyacinth grows abundantly in eutrophic water bodies and leads to an imbalance in the ecosystem dynamics of the water body.
(2) The amount of some toxic substances of industrial waste water increases in the organisms at successive trophic levels.
(3) The micro-organisms involved in biodegradation of organic matter in a sewage polluted water body consume a lot of oxygen causing the death of aquatic organisms.
(4) Algal blooms caused by excess of organic matter in water improve water quality and promote fisheries.
Answer: Option (4)
Explanation:
Water hyacinth is an invasive aquatic plant that proliferates in eutrophic water bodies and
disturbs ecosystem balance, so statement (1) is correct.
Toxic substances from industrial waste water undergo biomagnification,
leading to increased concentration at successive trophic levels,
so statement (2) is correct.
Micro-organisms decomposing organic matter in sewage polluted water consume large amounts
of dissolved oxygen, resulting in hypoxia and death of aquatic organisms,
so statement (3) is correct.
Algal blooms formed due to excess organic matter actually deteriorate water quality by
blocking sunlight and reducing dissolved oxygen; they do not improve water quality or promote fisheries.
Therefore, statement (4) is NOT correct, making Option (4) the correct answer.
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