July 14, 2022 at 12:24 p.m.
Warm weather may bring about blue green algae blooms
Warm weather may bring about blue green algae blooms
Gina LaLiberte is the Department of Natural Resources (DNR) statewide harmful algal bloom coordinator and has done many presentations for the public on the dangers of Cyanobacteria as well as how to identify blooms. Cyanobacteria, she has said, is present in all waterbodies, but only becomes a problem in some. Planktonic cyanobacteria is seen floating in the water. It looks like tiny green specks or a green "dust" on the water. They tend to be a mint green color while they are actively growing, she said.
The Jar Test
The "jar test" as it is known, is an easy way to determine if a person is looking at cyanobacteria. It is conducted by scooping some lake water into a jar and shaking the jar. Once it has settled, cyanobacteria will float to the top of the water. True algae will usually sink, she said. The Minnesota Pollution Control Agency has a document explaining the test. It is easy to find by searching "Minnesota jar test" on the internet.
LaLiberte said it is important to look closely at the jar, however. Small plants such as duck weed or water meal can be confused with algae, but are plants. Duck weed will have roots which can be seen upon closer inspection.
The Stick Test
The "stick test" can help determine if floating green mats are Cyanobacteria or filamentous green algae. LaLiberte said if a stick put into the green mat comes out looking as though it is covered in green paint, it is likely Cyanobacteria. If it resembles long, green hair, it is likely filamentous green algae, which is not harmful. Color is important here, she said, as Microseira, a type of cyanobacteria, can look hair like, but will look black to the naked eye.
Blooms
Excessive growth of Cyanobacteria to nuisance levels are blooms. Some cyanobacteria can make individuals sick if they are ingested. Some people can also have skin irritations from cyanobacteria. For that reason, these blooms are called Harmful Algal Blooms or HABs. No official quantification exists, where a level can or cannot be considered a bloom, however.
LaLiberte said nuisance levels of plankton cyanobacteria can make the water look green. A "pea soup" color and look to the water is a good indicator of a HAB, she said.
Large blooms tend to occur in lakes that have high nutrients as it takes a great deal of nutrients to fuel growth of blooms. During calm conditions, planktonic scums can float to the surface and form. Unusual colors can be pigments being released from blooms as they start to break down.
Blooms can also be caused by wind blowing Cyanobacteria across the lake. This can happen even in lakes with low nutrient levels when calm conditions are followed by some wind for several days. The blooms will be pushed into bays and shorelines by the wind. For that reason, they may show up in places they are not normally seen on a lake.
Floating mats from the lake bottom can come to the surface in late summer. This happens more in lakes with clear water, LaLiberte said. They grow on the bottom, using photosynthesis, until they float to the top.
HABs come in a variety of colors as well. They can be blue, green, brownish, or even white. In general, if something seems different, the best course of action is to avoid the area.
What causes blooms?
Cyanobacteria require excessive nutrients to fertilize bloom growth. Warm water and calm weather promote scums. Cyanobacteria grow well in warmer water, as is seen in mid summer in the Northwoods. Scums will form in calmer weather. Shallow reservoirs and impoundments are more vulnerable to blooms as well. Blooms, though, can happen in any waterbody.
The exact cause of a bloom on a particular waterbody may be very complex, she said. It could have something to do with nutrient inputs years ago, other species in the waterbody and a variety of other things.
Protection
Blooms of highest concern can be seen with the naked eye. While not all blooms create toxins, it is best to assume toxins are present. People and pets should do their best to stay away from shallow, warm and stagnant waters. Blue-green algae mats may have formed on the bottom in areas such as these and may dislodge with any activity.
LaLiberte said it is best to stay away from any place with "lots of organic stuff." This could indicate high bacteria levels. Areas such as this may also have cyanobacteria blooms hidden in them.
"When in doubt, keep out!" LaLiberte said. Lake-goers should avoid swimming and boating through blue-green water scums and "pea soup" water. If an adult cannot see their feet in knee-deep water, it is best to move on to another location.
When swimming with children and pets, it is best to choose the clearest water possible. Even then, it is best to avoid swallowing water whenever possible, no matter how clean it looks.
Children and pets, as well as adults, should shower as soon as possible after swimming in a lake, river or pond. This will work to wash away any bacteria that may have been present in the water, even if it looked clean.
LaLiberte said signs of cyanotic poisoning, water intoxication and heat stroke can seem similar in dogs. Give dogs frequent breaks from playing in the water. When throwing object in the water, flat objects will minimize water ingestion. She also recommended providing shade and clean drinking water for dogs while at the beach.
More information about Cyanobacteria can be found on the DNR website and harmful blooms can be reported via email at [email protected].
Beckie Gaskill may be reached via email at [email protected].
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