Blue-green algae - Cyanobacteria
Blue-green algae are a group of photosynthetic bacteria that many people refer to as "pond scum." Blue-green algae are most often blue-green in colour, but can also be reddish-purple, or brown. Blue-green algae generally grow in lakes, ponds, and slow-moving streams when the water is warm and enriched with nutrients like phosphorus or nitrogen.
When environmental conditions are just right, blue-green algae can grow very quickly in number. Most species are buoyant and will float to the surface, where they form scum layers or floating mats. When this happens, we call this a "blue-green algae bloom”.
Even if you can't see blue-green algae floating on the surface of the water, that doesn't mean they aren’t there. Blue-green algae can be suspended at various depths in the water, and their location depends on a number of factors. The most important of these are light and nutrients. Many species of blue-green algae have evolved to be able to control their buoyancy as the availability of light and nutrients change with the time of day and local weather conditions. At night, when there is no light, cells are unable to adjust their buoyancy and often float to the surface, forming a surface scum. So this scum can literally appear overnight and may linger until wind and waves scatter the cells throughout the water body.
When the numbers of blue-green algae are not excessive they, together with other algal groups, are important contributors to the aquatic biology of natural waters. They convert energy from sunlight into chemically useful forms, liberate oxygen into the water, take up minerals and produce substances which enter and support food chains. They are capable of producing TOXINS. These toxins have caused the death of wild animals, and domestic pets. In humans, rashes have occurred following skin contact, and illnesses have occurred when blue-green algae have been swallowed.
THIS POND CONTAINS BLUE-GREEN ALGAE. DO NOT LET DOGS SWIM IN THE POND. DOGS MUST BE KEPT ON A LEAD IN THIS AREA.
Stealth may be required when fishermen are in attendance.