What Are Algae?
Aparna Vidyasagar
Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis. By virtue of these characteristics, the general term algae includes prokaryotic organisms — cyanobacteria, also known as blue-green algae — as well as eukaryotic organisms (all other algal species). Their cells are more organized. Though they are capable of conducting oxygen-producing photosynthesis and live in many of the same environments as eukaryotic algae, cyanobacteria are gram-negative bacteria, and therefore are prokaryotes. In freshwaters, cyanobacteria are the main toxin producers, though some eukaryotic algae also cause problems.