Cyanobacteria: What's the issue?

Cyanobacteria blooms and toxic events have been on the rise across Canada in recent years, from blooms so big you can see them from space in Lake Erie or small day-long-lived blooms in small lakes. As our summers stay warm and water temperatures remain high, risk for cyanobacteria blooms will continue. In the past year, four dogs have lost their lives due to ingesting cyanobacteria along the Wolastoq [St. John River] causing obvious concern for pet owners, researchers, government officials and river lovers.

So, what are cyanobacteria?

Cyanobacteria or blue-green algae as they are sometimes called due to confusion from early scientists who thought they were an algae, are actually photosynthetic bacteria. Some species, but not all, produce toxins that are toxic to humans and other vertebrates that cause different reactions from nervous system and organ impacts to gastrointestinal illness and skin irritation.

Cyanobacteria are naturally occurring in waterbodies and have existed for billions of years; however, human impacts on water quality can increase the abundance of cyanobacteria. Cyanobacteria thrive in warm waters with excess nutrients. Many human activities can cause an increase in the availability of nutrients entering our lakes and rivers, particularly phosphorus.

Phosphorus can be found in many sources including:

  • cleaners

  • fertilizers

  • runoff from lawns, agricultural land, and forestry operation sites, and

  • is naturally occurring in topsoil and sediment

When phosphorus levels are high, cyanobacteria can quickly dominate the habitat with these extra nutrients, creating either a bloom or an abundance of benthic mats.

Through research in the Lawrence lab at UNB Fredericton, it has been discovered that in the Wolastoq [St. John River] there are two types of cyanobacteria of concern: species that form surface blooms and species that form mats.

Example of a surface cyanobacteria bloom in a New Brunswick

Example of a surface cyanobacteria bloom in a New Brunswick

Surface bloom forming cyanobacteria are more common and what people generally think of when the issue of cyanobacteria comes up. These are the blooms that you can see on the surface or in the water column that look green or blue-ish green and will form in warm, slow moving water like the many lakes and bays within the watershed. These blooms can still contain species capable of producing toxins, the most common being microcystin, that are known to cause skin irritation, gastrointestinal illness, and liver damage.  Many lakes have had advisories for these blooms – Grand Lake, Lac Baker, Washademoak Lake, and Nashwaak Lake to name a few. A full listing of cyanobacteria advisories can be found here:

Example of a surface cyanobacteria bloom in New Brunswick

Example of a surface cyanobacteria bloom in New Brunswick

The newly discovered large cyanobacteria mats in the river are made of up species capable of creating potent neurotoxins (anatoxins) are far less studied and a new concern in our river system. Unlike a surface bloom, these mats can be present in water that looks completely clear with only a scum on the rocks and therefore looks okay for swimming, increasing the risk of exposure to these toxins. The Environment Canterbury Regional Council states that benthic cyanobacteria mats present as “substrate covered in thick brown or black mats that have a slimy/velvety texture and earthy/musty smell”.

According to researchers at UNB, these mats have formed in many areas along the main stem of the river on cobble and muddy substrates and have also been found on other aquatic vegetation. When they grow to an abundance or ‘bloom’, parts of the mat can be broken off and travel downstream where it can get washed up on shore. This causes people and pets to be exposed fairly easily if walking along the waters edge. Exposure to these toxins through ingestion or inhalation of aerosols can be fatal to everything with a nervous system. Have a listen to this interview with Dr. Janice Lawrence to learn more about her research.

Example of a cyanobacteria benthic mat found in New Zealand (photo from RNZ: )

Example of a cyanobacteria benthic mat found in New Zealand (photo from RNZ:

Reduce your risk

To reduce your and your pet’s risks to cyanotoxins exposure, inspect the water and substrate for cyanobacteria, avoid contact with the water when cyanobacteria advisories are in place, do not ingest or drink any contaminated water – even boiling will not remove toxins - and inform the New Brunswick Department of Environment and Local Government Regional office in your area if you suspect a bloom.

What can you do to help?

  • Reduce the use of phosphorus on your property

  • Reduce runoff into waterbodies by creating or protecting buffer areas between the lawn and watercourses by planting native trees and shrubs

  • Install rain gardens and rain barrels to reduce over-land runoff

  • Prevent erosion by keeping streambanks and riparian areas naturalized with good tree and shrub cover

  • Properly maintain septic systems

To learn more about cyanobacteria in the Wolastoq and expert recommendations have a listen to this three part expert panel here:

Part one -

Part two -

Part three -

Want to learn even more? Here is some additional reading:

Blue-green algae in New Brunswick Lakes: Questions and Answers

Government of Canada’s cyanobacteria and cyanotoxin guidelines for recreational waters

New Brunswick Department of Environment and Local Government - Algae