Which term describes extremely small plankton, typically less than 2 micrometers, including many cyanobacteria?

Which term describes extremely small plankton, typically less than 2 micrometers, including many cyanobacteria?

• A. Phytoplankton
• B. Picoplankton
• C. Plankton
• D. Nekton

Answer: (B)

Size-based classifications of plankton identify picoplankton as the group consisting of the tiniest cells. These are typically less than 2 micrometers in diameter, and they include many cyanobacteria, such as Prochlorococcus and Synechococcus, which are abundant in many ocean waters. The reason this term fits best is that it specifically designates that extremely small size class, capturing what the question describes. Broader terms don’t fit as well: phytoplankton covers photosynthetic plankton of all sizes, plankton is the entire drifting community, and nekton refers to larger, actively swimming animals rather than drifting microorganisms.

Size-based classifications of plankton identify picoplankton as the group consisting of the tiniest cells. These are typically less than 2 micrometers in diameter, and they include many cyanobacteria, such as Prochlorococcus and Synechococcus, which are abundant in many ocean waters. The reason this term fits best is that it specifically designates that extremely small size class, capturing what the question describes. Broader terms don’t fit as well: phytoplankton covers photosynthetic plankton of all sizes, plankton is the entire drifting community, and nekton refers to larger, actively swimming animals rather than drifting microorganisms.