What is the significance of dissolved reactive phosphorus (DRP) in water quality?

• A. DRP is not bioavailable to aquatic life.
• B. DRP is 100% bioavailable to aquatic life, unlike total phosphorus which includes sediment-bound phosphorus.
• C. DRP is less bioavailable than total phosphorus.
• D. DRP is only present in wastewater.

Answer: (B)

Dissolved reactive phosphorus is the portion of phosphorus that’s dissolved in water and in a form that aquatic organisms can take up readily. Because it’s in solution, it moves with the water and becomes available quickly, so it can fuel rapid algal growth and contribute to eutrophication. Total phosphorus includes both this dissolved portion and particulate forms, including phosphorus bound to sediments, which are not immediately available to organisms. That distinction is why DRP is the more relevant measure for predicting short-term nutrient-driven water-quality impacts: it represents the fraction that can be immediately used by algae and aquatic plants. The other statements don’t fit because DRP is indeed bioavailable, it’s not limited to wastewater, and while DRP is the most readily available form, the choice’s claim of 100% bioavailability is a simplification; the core idea is that DRP is the readily usable portion, driving quick ecological responses.