Figure 1.7 Cyanobacteria. Also known as blue-green algae, cyanobacteria are bacteria capable of conducting photosynthesis. These organisms can grow rapidly under highly fertile conditions, producing large floating mats in the water that can be toxic to animals, as illustrated in this photo of Lake Mendota, Wisconsin.

Photos by Lee Wilcox (top) and M I (Spike) Walker/Alamy (inset).