Which of the following is NOT a common type of planktonic algae?

Waterhyacinth is not a type of planktonic algae because it is a rooted aquatic plant rather than a form of algae. Planktonic algae are typically unicellular or colonial organisms that float in the water column and are primarily responsible for photosynthesis in aquatic environments.

Microcystis, Nostoc, and Chlorella, on the other hand, are all examples of types of algae. Microcystis is a genus of freshwater cyanobacteria that can form harmful algal blooms. Nostoc is a genus of cyanobacteria that can exist as free-floating colonies or in a symbiotic relationship with plants. Chlorella is a green microalga known for its high photosynthetic efficiency and is often studied for its potential health benefits.

In summary, while Microcystis, Nostoc, and Chlorella are all categorized as planktonic algae, Waterhyacinth is a vascular plant and therefore does not belong to the same category.