Answer:
A: A decrease in the watershed’s biodiversity, which will reduce its ability to supply clean and safe drinking water.
Step-by-step explanation:
As already indicated, algal bloom resulting from excessive enrichment of watersheds by pollutants leads to a decline in dissolved oxygen level available for other aquatic organisms. Consequently, aquatic starts dying off due to inadequate oxygen, otherwise known as hypoxia.
The death of aquatic organisms results in a decreased watershed's biodiversity which in turn affects some ecosystem services, including water purification.
Potential water pollutants are usually filtered off or bioremediated as water moves through the various aquatic biodiversity, leading to the promotion of clean and safe drinking water.
Hence, a decrease in water biodiversity will eventually reduce its portability.
The correct option is A.