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Headings: What causes algae blooms? Name that algae. Is algae bad? Can I get rid of it? Excessive amounts of nutrients that enter our lakes leads to eutrophication (accelerated plant growth). Sometimes plant growth may be in the form of nuisance algae that “bloom,” turning the water pea green and sometimes even causing fish kills. Algal blooms are an unusually dense growth of aquatic single celled plants (algae). They occur, frequently to the point where they discolor the water, when ideal factors combine to promote growth—generally light, temperature, salinity and nutrients. Algal blooms are a natural phenomenon but their frequency, duration, extent and density are all increased in waters where human activities on land increase nutrient runoff. If your algae look like fluffy clouds or cotton candy, there’s a good chance it’s probably filamentous algae, sometimes called “moss” or “pond scum.” Cladophora feels “cottony,” while spirogyra is bright green and very slimy to the touch, and pithophora (or “horse hair”) has a very coarse texture like horse hair or steel wool. As algae grows, it produces oxygen that gets trapped in the entangled strands of algae. This entrapped oxygen makes the algae buoyant and causes it to rise to the surface. Algae are necessary for a healthy lake ecosystem, but there can be too much algae. When this happens, the grazers who eat the algae can’t keep up. As the uneaten algae die off, they sink to the lake bottom and decay. The process of decay requires bacteria, which in turn require oxygen. If there is an abundance of dead algae, bacteria use up too much oxygen, and there isn't enough left over for all of the animals, like insects and fish. Too much algae can also give lakes an unpleasant green color or a surface scum. Unlike toxic blue-green algae which is blue-green in color (but can be brown or purple) and appears cloudy or like thick pea soup, Cladophora, pithophora and spirogyra are from the green algae family. Green algae don’t produce toxins but it is still important to think about practicing good hygiene, such as washing off, if you come in contact with it. Short term, the best method for homeowners to remove filamentous algae is to rake out the floating clumps and compost these piles or use them in your garden as mulch. Chemical control requires a permit from DNR. Long term, lake property owners and farmers can limit the amount of water and nutrients reaching the lake. Reducing fertilizer use, maintaining septic systems, keeping animal waste out of water ways and storm drains, preventing soil erosion on farms and construction sites, planting buffers along waterways, and keeping leaves and grass clippings out of the streets are just a few of the ways that we can all reduce phosphorus runoff over the long run to help keep the problem from getting worse. |
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