DorsetEnvironmentalScienceCentre 15 All about Algae Algae are critical to the life of our lakes.At the base of the food chain algae convert nutrients to organic matter and oxygenate the water.Without algae there would be no fish. Thousands of species of algae live in Ontarios waters and shorelines. Some are microscopic simple cells while others can grow as mass aggregates of cells or in strands or even resemble plants. Algae thrive in areas where water is shallow slow moving and warm with ample available nutrients and visible blooms most commonly occur during late summer and fall. Many factors influence algal growth such as the amount of light that penetrates the water the concentration of nutrients in the water water temperature the surrounding food chain microscopic animals and fish that graze on algae parasitism by bacteria and fungi competition from aquatic plants for nutrients. Because algae produce oxygen as a by-product of photosynthesis and also take in oxygen for respiration a lake that has a large population of algae can experience great fluctuations in dissolved oxygen concentration which can stress fish and other wildlife in the lake. Nutrient sources such as detergents septic tank leaks and fertilizer runoff from lawns and gardens can increase algal growth or blooms. For this reason it is important to limit nutrients that enter your lake. see Page 3 Blue-Green Algae Some species of algae referred to as blue-green or cyanobacteria can release toxins that can be harmful to the health of both humans and animals. Do not swim drink or eat fish from an area with a suspected blue-green algal bloom. Note boiling water will NOT remove these toxins. Dense blue-green algae blooms may make the water look like green pea soup or turquoise paint. Report all suspected sightings of blue-green algae by calling the Spills Action Centre 1-800-268-6060. For tips about recognizing suspected blue-green algae find links at httpfoca.on.cafact-sheets-videos.