Watersheds may be contaminated by fertilizers and other pollutants. When these substances enter a waterway, they can cause algal blooms, which are rapid overgrowths of algae. When the algae die, the decay uses up a large portion of dissolved oxygen. Declining oxygen levels can then cause large die-offs of animals in the waterway.



What will an algal bloom in a watershed most likely cause?

A

a decrease in the watershed's ecosystem diversity, which would improve its ability to supply large volumes of water

B

an increase in the watershed's species diversity, which would improve its ability to supply large volumes of water

C

a decrease in the watershed's biodiversity, which would reduce its ability to supply clean and safe drinking water

D

an increase in the watershed's genetic diversity, which would reduce its ability to supply clean and safe drinking water