Effects on the Lake

These cyanobacterial blooms pose a problem for a few reasons.

  1. When the blooms are large enough, they can produce thick mats on the surface of the water.  This may make various activities on the water difficult and can have an impact on the tourism industry.[3]
  2. Another serious problem is that some species can produce, and when they bloom near water intake pipes (like what happened in Toledo) they can poison the water.  This may make water activities dangerous due to risk of ingesting toxins.
  3. Additionally, the decomposition of the organisms can deplete the oxygen from the surrounding area, which can kill off fish and other higher organisms.  This could effectively kill the lake.  These dead zones can also change the water chemistry to allow heavy metals in the sediment of the lake to be reabsorbed, adding another toxic element to the lake.

For all of these reasons, it’s important for people to understand the nature of the organisms, what to do if a bloom is encountered, and what can be done to reduce or fix the problem.

Effects on People and other Animals

Since the toxic organisms are quite diverse, the toxins produced by them are diverse as well. The toxins can affect all higher life including plants, though the effects will differ from species to species.  Most importantly these toxins can affect humans, pets, livestock and fish.  The most common toxin (called microcystin) affects the liver, but causes a number of serious symptoms to other parts of the body as well.  Some general toxin symptoms are listed in the chart below.  These toxins can be fatal if ingested in large quantities, or even if consumed in smaller quantities over a long period of time. Although few humans have ever died from consuming microcystin, other animals (including pets and livestock) have not been so lucky.[6]


Image courtesy of Kansas State University.

See page: what to do if you are affected.