What is blue-green algae?
Blue-green algae, technically known as cyanobacteria, are microscopic organisms that are naturally present in lakes and streams. Under certain conditions, blue-green algae can become abundant in warm, shallow, undisturbed, nutrient-rich surface waters that receive a lot of sunlight. When this occurs, blue-green algae can form blooms that discolor the water or produce floating mats or scums on the water’s surface.
Blooms can also form on rocks, along the shoreline, and at the bottom of a waterbody. Blue-green algae blooms and the toxin they produce, microcystin, are known for making people (and particularly pets) sick. Blue-green algae blooms typically happen in mid-to-late summer. Warm weather and plenty of sunshine, as well as increased nutrients, are the key factors.
What is cyanobacteria?
Blue-green algae isn’t an algae at all. It’s actually a bacteria called cyanobacteria, a division of microorganisms that are related to the bacteria. The name cyanobacteria refers to their color (from Ancient Greek κυανός (kuanós) ‘blue’), giving them their other name, “blue-green algae”, though modern botanists restrict the term algae to eukaryotes and do not apply it to cyanobacteria, which are prokaryotes.
Cyanobacteria are prokaryotic and represent the earliest known form of life on the earth. Unusually, cyanobacteria are able to photosynthesize – that is, use light to create food, which is something typically only seen in plants. There are many different species of cyanobacteria, and each one is different. In fact, the saltwater variant of cyanobacteria doesn’t look blue-green at all. Instead, it’s a slimy, reddish-brown color.
What causes blue-green algae blooms?
Blooms typically occur in late summer, when the water and weather are warm and extra nutrients enter the lake. Such nutrients typically come from a variety of sources, including storm water runoff, nearby facilities and agriculture.
“Blooms typically occur in late summer, when the water and weather are warm and extra nutrients enter the lake. Such nutrients typically come from a variety of sources, including storm water runoff, nearby facilities and agriculture.”
The top two nutrients that contribute are phosphorus and nitrogen. When these two are introduced into lakes in large amounts, blue-green algae (and other species of algae and weeds) can become out of balance with other plants and animals. They spread quickly and smother other kinds of aquatic plants. Then, the algae grows and multiplies until it uses up available resources. When the bloom begins to die, it releases a toxin (microcystin) if the cells contain it.
What does blue-green algae look like?
During its peak, a cyanobacteria bloom will look like paint or pea soup on the surface of still water. It can perculate down into the water column, rather than stay on the surface, and sometimes cells can clump together, but they will not be picked up easily. In fact, blue-green algae are not true algae, which is why cells interact with water differently than true algae, almost appearing to be a part of a water.
Although we call them algae, because they are free-floating and grow in aquatic colonies, in fact, blue-green algae are a type of bacteria – cyanobacteria. That means that it is not possible to identify individual cells or roots, like you can with aquatic plants. A blue-green algae bloom can change depending on the time of year and at different points in its lifecycle. For example, a dying bloom is less vibrant, more muted, still paint-like.
Does blue-green algae always produce microcystin?
Cyanobacteria are unpredictable, and a bloom will not always produce microcystin. It always has the potential to, though, and that is why the authorities recommend staying away from water that has a visible bloom. There is no way to tell if the bloom is toxic until the water is tested. Unfortunately, pets and livestock will drink from and bathe in any available water source in summer, and illnesses and deaths can happen if animals consume large amounts of water containing blooms, scums or benthic mats.
Another environmental problem with cyanobacteria is that it multiplies quickly. And as it does, it can cover vegetation in a slimy film that is thick enough to block out light, and plants need light for energy. Without it, they will eventually die. Unfortunately, because blue-green algae isn’t actually an algae, traditional algae killers don’t have much effect.
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