Cyanobacteria 101: Blue-green Algae

Cyanobacteria 101

(Blue-green algae)

There is growing concern over those tiny algae-like creatures, commonly called blue-green algae.  Technically they are a type of bacteria that is commonly found in ponds and lakes.  The acronym for these creatures is HAB (harmful algae blooms.)  The fall issue of LakeLine, journal of the North American Lake Management Society (NALMS) is devoted exclusively to HABs.

The central question is: What kind of threat do these organisms pose to public health?

Here is the problem.  A few species of cyanobacteria are capable of producing toxic chemicals.  These species do this to protect themselves from predators.  Unfortunately, some of those toxins can harm people, producing liver and kidney damage. 

Perversely, cyanobacteria toxins are more poisonous to wildlife, farm animals and humans than to aquatic life.  I expect millions of years of natural selection generated changes in the DNA of aquatic organisms to enable them to adjust to the toxins.

Dogs, with their penchant to drink from ponds and shallow lakes, are particularly vulnerable to death by ingestion of toxic algae.

According to LakeLine, the effect of cyano-toxins on humans is a function of the concentration of cyanobacteria cells in the water.

Here are the symptoms:

  • Itchy skin rashes
  • Hay fever like symptoms
  • Gastro-intestinal upset
  • Allergic reactions
  • Headaches,
  • Mouth blistering
  • Fever

LakeLine reported a study that found that “people who used personal watercraft on lakes with high cyanobacteria concentrations were twice as likely to report symptoms, particularly respiratory symptoms, than those who used their personal watercraft on lakes with lower cyanobacteria concentrations.”  I’m guessing ingestions of direct spray may be the conduit for HABs to enter the body.

Most Minnesota lakes do not pose threats to water lovers, but a few do:  shallow lakes with intensive algal blooms in the heat of a hot summer can put humans, and particularly dogs, at risk.

There are no federal regulations on acceptable levels of cyanotoxin concentrations, although the World Health Organization has some guidelines.  Lack of such information can put health officials and resource managers in a difficult dilemma.  Do you close a body of water that curtails tourism in an area but where the cyanobacteria concentration actually is within acceptable limits?  Or, do you keep the beach open, running the risk that cyanobacteria concentrations are actually not safe?

Oklahoma has taken the lead on this issue.  They passed legislation that requires the Oklahoma Tourism and Recreation Department to provide monitoring information about HABs to the public via a website

Darby Nelson

One Response to Cyanobacteria 101: Blue-green Algae

  1. ted redalen

    with the onset of contract
    poisoning in southern minnesota
    area lakes a few years back which
    kills all the vegetation in the
    whole lake i have seen much
    heavier concetrations of algae
    and the water is cloudier overall
    contiuously in east lake
    jefferson in le sueur county than
    it was prior to the heavy

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