Under which circumstances should we try to control the population numbers of pfiesteria?

Pfiesteria species generally found in estuaries, the population of which are needed to be controlled only when they becomes toxic. Presence of large of fish triggers toxicity in Pfiesteria.

Explanation:

Pfiesteria are known to be associated with fish kills as for example large fish kill in the seas of North Carolina. It also causes blooming of algae in enormous numbers thus make the water bodies, hostile for survival of fishes and other marine lives. It affects human too by release of toxins in air and water often resulting in respiratory problems, infections of gastrointestinal system, headaches and fatigue. In this type of grave circumstances, leading to outburst of population of Pfiesteria, there is an urgent need to control.

a

explanation:

correct answer is a. and d.