Cyanobacteria are a type of photosynthetic bacteria commonly referred to as blue green algae. Like many bacteria, some cyanobacteria can produce toxins harmful to humans, pets, livestock and wildlife. When cyanobacteria begin to grow rapidly this can result in a bloom, which is a dense and often scummy accumulation of cyanobacteria cells and colonies. During blooms, the cyanobacteria become the dominant life in their environment. This is also the time when the largest number of toxins are found in water, representing the greatest threat to public health.