Question

Sudden mass death of fish is likely to occur in
A) Eurotrophic lake
B) Mesotrophic lake
C) Oligotrophic lake
D) Olixotrophic lake

Answer 1

Hint: The sudden mass death of water animals mainly fishes occur due to the depletion of oxygen in the water body. We should be well aware of the characteristics of the given lakes to identify which among is the one that causes this fate.

Complete answer:
We might be aware of the term Eutrophication. This process that occurs is the main cause behind the sudden mass death of fishes in the water body. The eutrophic lake is where this sudden death occurs.

The accumulation of organic mass in the water body leads to the depletion of the dissolved oxygen in the water which is caused due to the decomposing bacteria. Along with this, there is also seen the growth of algal mass which occurs due to the organic and inorganic nutrients that leads to eutrophication. This causes the atmospheric oxygen to stop combining with the water body. The algal bloom even contributes to the build-up of the organic mass. Therefore, it all leads to a condition called hypoxia i.e. depletion of oxygen in the water body that leads to the death of the fishes. There can be seen a huge mass of dead bodies that float in the body due to depleted oxygen.

Therefore the correct answer is option ‘A’.

Note: Eutrophication is considered a serious threat to the environment as it results in the degradation of water quality as well as the depletion of oxygen in the water body leading to loss of living organisms in it. Eutrophic water can reach a point where it becomes a “dead zone” which cannot support life.