Hot topic: Understanding blue-green algae

Hot topic: Understanding blue-green algae

Sunday, July 11, 2021 - 11:00am
DARYL BAUER Nebraska Game and Parks Commission         

It is midsummer, it is hot and that means prime time for blue-green algae blooms.

There is not a body of water here that does not have blue-green algae, which has been present in Nebraska waters forever.

There are many species and types of algae. Different groups or families of algae bloom throughout the year. Under certain conditions, one type of algae will bloom and die off, then another type will bloom and replace it. This happens year-round. Blue-green algae is just one group, one family of algae that tends to dominate during the warmest months.

Blue-green algal blooms typically look like pea green soup or like someone spilled a can of John Deere green paint on the water. Some species may look like grass clippings floating on the water. It typically is found along windblown shorelines. If you see water like that, avoid bodily contact and ingestion. Keep your pets out, too.

In the blue-green algae family, some species produce toxins called microcystins. Those toxins are produced only under certain conditions. The microcystins are released by the blue-green algae while they are alive; they do not have to die to release the toxins. However, microcystins can persist for some time, usually days, after the algae dies.

Blue-green algae thrive in fertile waters. There is not a body of water in Nebraska that could be considered infertile. Blue-green algae typically blooms and dominates when nutrient levels, particularly phosphorus, are elevated. Elevated phosphorus levels are a particular problem in man-made waters with years of silt and sediment accumulation. Nutrients are carried on those sediments. Housing developments around water bodies, fertilizers from lawns, and nutrients leaching from septic systems also can add nutrients to the aquatic ecosystem and eventually fuel blue-green algae blooms.

Nobody worried about them until a few years ago because nobody tested for blue-green algae toxins. In recent years, technology has made the tests easier and less expensive. Also, a few years ago, some pets died near a private sandpit and testing done on those pets attributed their deaths to microcystins.
Following that incident, Nebraska’s Department of Environment and Energy began testing waters around the state for microcystins. Testing is done weekly and you can see the results and any health alerts that have been issued at
NDEE tests water bodies for the presence of microcystins. It would be senseless to test for blue-green algae because blue-green algae is everywhere, and only certain species produce toxins under certain conditions. It can be present without there being elevated levels of microcystins.
Health alerts are issued when microcystin levels exceed action levels. NDEE does not take samples all over a body of water. Sampling is concentrated in areas of heavy use, especially swimming areas.
Action levels for health alerts have changed in recent years. When microcystin levels exceed 8 ppb, NDEE issues a health alert advising people to keep themselves and their pets out of the water and avoid bodily contact and ingestion of water. Activities such as swimming and water skiing would not be recommended, but activities such as fishing need not be curtailed.
The blue-green algae toxins do not persist in the flesh of fish, so even though there may be a blue-green algae health alert, it does not mean you cannot consume fish from that body of water. Tests are done on water bodies around the state every week. Health alerts are issued weekly and now last for only one week.
Blue-green algae toxins do not directly cause fish kills. Extreme algae blooms can cause fish kills due to overnight oxygen sags, but microcystins do not kill fish. Algae blooms can be so thick that fish may be difficult to catch in those areas or they may move to areas of clearer water, but the algae does not affect fish behavior.