Answer: The given statement is False.
Phytoplanktons play a significant role in the aquatic ecosystem. By performing photosynthesis, they provide food source to other organisms. They form the basis of the aquatic food web.
An increase in the number of phytoplankton is always not beneficial because it can result in the Harmful Algal Blooms ( HAB).
Harmful algal blooms refer to the tremendous growth of algae in the aquatic ecosystem. These blooms release highly toxic compounds which have a deleterious impact on aquatic as well as terrestrial lives.