Blue-Green Algae: A Growing Problem

Blue-Green Algae:  A Growing Problem

by Steve Auger

Blue-green algae, also known as cyanobacteria, is a type of bacteria that has been around for billions of years, providing a significant contribution to the marine environment by reducing carbon and nitrogen, while producing oxygen.  In most cases cyanobacteria is harmless but sometimes the blue-green algae produces toxins that can significantly affect the health of humans, animals and fish alike.


Meech Lake, 30 minutes from Ottawa (Canada) had one beech shut down during the summer of 2007 as a result of toxic blue-green algae.  

The frequency and duration of blue-green algae blooms have been increasing in Canadian fresh water lakes.  This may be a result of increasingly hot summers and increased nutrient (phosphorus and nitrogen) concentration.  Nutrients enter into lakes and rivers due to many human activities including use of detergents  and phosphorus-based fertilizers as well as discharge of untreated sewage.

Toxic Cyanobacteria

The toxins produced by blue-green algae are summarized in the table below:

Toxin	Example	Symptoms
Dermatotoxins Gastrointestinal	Lyngbyatoxin lipopolysaccharide endotoxins	Allergy-type reactions such as rashes, eye/nose/throat irritation, and asthma Headaches, fever, and gastroenteritis (nausea, stomach cramps, vomiting, diarrhea)
Hepatotoxins	Microcystins nodularins	Gastroenteritis, tissue damage, muscle weakness, paralysis, and respiratory failure (with acute exposure) Tumors, and possibly liver cancer (with long-term, chronic exposure)
Cytotoxins	Cylindrospermopsin	malaise, headache, anorexia, vomiting, chromosome loss, DNA strand breakage, and damage to organs
Neurotoxins	anatoxin-a saxitoxin (associated with paralytic shellfish poisoning)	seizures, paralysis, respiratory failure or cardiac arrest

Note:  The source of the above information is from Wisconsin Department of Natural Resources

Exposure to Toxins

Exposure to these toxins can occur through skin contact (swimming), through inhalation (water skiing or boating), or by swallowing contaminated water.  Children are at greater risk than adults because they do not understand the health risks (e.g. they may swallow water) and they weigh less.

Some cyanobacteria toxins are known to accumulate in the liver and kidneys of fish and shellfish.  The W.H.O. advises that people who eat fish (originating from water where blue-green algae bloom is suspected) should do so in moderation.  Care should be taken not to cut into organs when filleting the fish and the fish should be rinsed thoroughly with clean water.  The guts of the fish should not be eaten.

What Can Be Done?

As an individual you can minimze your ecological footprint by:

• Eliminate fertilizer particularly on lawns;  use phosphorus-free fertilizer when necessary
• Use only phosphorus-free detergents for daily living
• Fix leaking septic systems

As an (government or business) entity:

• Maintain native vegetation along lake/river shorelines
• Minimize activities that result in erosion