You may notice a green, red or brown film on your favorite boating or swimming area in the summer. This coloring could mean that the water is affected by harmful algal blooms. Harmful algal blooms are an accumulation of tiny organisms known as algae and can release harmful toxins into the environment. Pictured is Microcystis ehrenbergii from Pinto Lake, California under light microscopy.
Credit: Dr. Barry H. Rosen , U.S. Geological Survey