Question

A lake with an inflow of domestic sewage rich in organic waste may result
A) Dry of the lake very soon due to algal bloom
B) An increased production of fish due to lot of nutrients
C) Death of fish due to lack of oxygen
D) Increased population of aquatic food web organisms.

Answer 1

Due to being rich in organic waste, the growth of algal bloom and other aquatic species takes place and decreases the amount of oxygen level in water.

Complete answer:
First we should know about water pollution to answer this question. The contamination of seas, oceans, lakes, groundwater, rivers, and reservoirs constitutes water pollution. This is normally activated because of human actions. Scientifically, water contamination affects the physical, chemical or biological properties of water, and can have a negative effect on any living organism.
Now, let us find the solution from the options-

The growth of algal bloom can occur due to the inflow of domestic sewage rich in organic waste, but the lake does not dry. Thus, the option A is incorrect.
Due to a lot of nutrients the fish not only increases in water, the growth of different aquatic species also takes place due to which they compete for each other for their nutrients and space. Thus, the option B is incorrect.
A lake rich in nutrients from domestic waste can contribute to eutrophication. Eutrophication is where nutrients become abundant in the environment. In underwater ecosystems, such as lakes, this can be a concern as it can induce growth of algal blooms and other aquatic plants. Thus, it will cause overcrowding and plants will fight for sunlight, oxygen, and space. It's enough to deoxygenate the water to kill fish and other species.
Due to growth of algal bloom, and other aquatic plants, the water becomes deoxygenated and causes death of many aquatic organisms. Thus, the option D is incorrect.

Thus, the correct answer is option C Death of fish due to lack of oxygen

Note: Water Pollution also affects the natural food chain. Small aquatic animals consumed toxins such as lead and cadmium. Later, fish and shellfish eat these species, and the food cycle continues to be affected at all higher levels.