Question

Noticing large amounts of algal growth in her small farm pond, a farmer adds about 20 grass carp to feed on the abundant algae and plants. After several years, the carp grow large, exceeding 20 pounds each in size. Late one summer, the farmer notices that the carp and most of the other fish are dead. The water also smells very bad. Which one of the following is the most likely explanation for the death of these fish?

A. the algae overgrew the pond and produced toxic levels of ozone
B. carbon dioxide released by the carp and algae eventually suffocated the fish in the pond
C. the large carp grew so large that they could not get enough oxygen
D. bacteria feeding on the large volume of carp feces depleted the oxygen

Answer 1

D. bacteria feeding on the large volume of carp feces depleted the oxygen

Step-by-step explanation:

In the context, it is given that in a small farm pond, the owner added 20 grass carp and feed them with the abundant plants and algae that is found on her pond. The carp grew large after many years but one summer the owner found the grass carps along with other fishes were dead.

The most possible explanation for the dead of the fishes in the pond because the bacteria feeds on the carp feces which depletes the dissolved oxygen present in the water. Thus the fishes could not breathe and were finally dead.

Therefore, the correct option is (D).