What are individual algae cells that are suspended on the surface of the water called?

Individual algae cells that are suspended on the surface of the water are known as planktonic algae. This term refers to algae that float freely in the water column, as opposed to being attached to surfaces or substrates. Planktonic algae are a vital component of aquatic ecosystems, contributing to primary production and serving as a food source for various aquatic organisms, including zooplankton and small fish.

Benthic algae, on the other hand, are those that grow attached to the bottom substrate of water bodies. Filamentous algae refer to algae that form long, thread-like structures, creating visible mats or tufts, and are often found attached to surfaces rather than floating freely. Rooted algae does not apply in this context since the term generally refers to algae anchored in sediments or dirt, not suspended in water. Thus, planktonic algae is the most accurate term to describe individual algae cells suspended in the water.