Over abundance of nutrients in the water is most likely to cause harm to which group of organisms?

A. Any organism that uses calcium carbonate to build support or protection.

B. Top tier predators that eat a lot of smaller fish

C. All organisms because it creates giant dead zones where nothing can survive.

D. Human populations through sea level rise

The flow of nutrients from the sewage and industries is the cause of the nutrient pollution in water bodies. These chemicals get accumulated in the water bodies affecting the aquatic ecosystem to a very large extent.

The increased level of nitrogen and phosphorus causes eutrophication which is also known as algal-boom. These nutrients cause the massive growth of algae which decreases the oxygen level of the water bodies. This increases BOD level of the water bodies which does not allow the growth of other aquatic species.

As a result of this, the dead zones are created where nothing can survive and therefore is the correct answer.

Thus, Option-C is the correct answer.