Blue-green algae, also known as cyanobacteria, are microscopic organisms found naturally in all types of water. In warm, nutrient-rich environments, cyanobacteria can multiply quickly, creating blooms that spread across the water’s surface. These blooms can create toxins that are harmful to humans and pets. Algal blooms at Blue Marsh Lake occur annually, however environmental and lake conditions from August through October enable the algal blooms to become potentially harmful.