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| Filamentous green algae, cyanobacteria/blue-green algae |
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Filamentous Green Algae Algae are a diverse group of simple organisms, once considered by scientists to belong to the plant kingdom. They form the base of most aquatic food chains and are therefore important to a healthy lake system. Some algae exist as single cells, others form masses with many cells clumped together. Some can swim, while others live attached to rocks or plants. One of the ways this varied group was historically classified was by their coloration, such as green, brown, red, golden-brown, or yellow-green algae. The green algae are common in lakes and sometimes get attention when certain types form green, stringy, often slimy-feeling masses as the result of high levels of nutrients. These are actually long strands, or filaments, composed of thousands of individual single-celled green algae connected end-to-end. The most common mat forming alga is Spirogyra; often studied in high school biology classes. When large quantities of green algae begin to decay, it can become a nuisance, creating offensive odors and depleting surface waters of dissolved oxygen. The resulting loss of oxygen can stress or even kill other aquatic organisms such as fish. Blue-Green Algae/Cyanobacteria Blue-green algae were once included with the other algae. It is generally agreed by scientists, however, that they should be classified with bacteria, an ancestral group, and be called cyanobacteria. Cyanobacteria can be important for supplying certain mineral nutrients to the aquatic environment, but generally do not serve as a primary food source like true algae. Under nutrient rich conditions, these microscopic single-celled or colonial organisms can multiply rapidly to form extensive "blooms" that cause the water to become green colored. They may eventually float to the surface and accumulate near shore as a thin bright green surface scum which cannot be picked up like a filamentous green algae mat. When a bloom dies, the water surface may become colored with a mixture of bright blue and white material, often mistaken for a paint spill. When in bloom, some blue-green algae may also contribute to potential health and water quality problems. For reasons not well understood, a few species occasionally produce toxins known to kill wildlife and domestic animals. They may also impart distasteful flavors to drinking water in addition to producing foul smelling masses as they die and decompose. |
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