Blue-Green Algae: A Potentially Toxic Visitor

For some communities in Ontario, the late summer-early fall period means the return of an unwanted and potentially dangerous visitor - blue-green algae blooms.

Blue-algae (cyanobacteria) occur naturally in ponds, lakes, streams and rivers. Usually invisible to the naked eye, under the right conditions the plant-like organisms multiply rapidly and form a mass or "bloom" on the surface of water bodies. Blooms are often blue-green and thrive in areas where the water is shallow, slow moving and warm, but they may also be present in deeper, cooler water.

One of the key factors contributing to the growth of blue-green algae is the amount of available nutrients such as phosphorus and nitrogen. Blooms can be caused by agricultural and stormwater runoff as well as leaching from septic systems. In Ontario, phosphorus tends to be the nutrient that influences the growth of algae, according to the Ministry of the Environment, Conservation and Parks.

Blue-green algae can be aesthetically unpleasant as they produce taste and odour compounds. During a "harmful algae bloom," toxins are produced. Exposure to these toxins can pose a health risk to humans and animals, causing fever, diarrhoea, abdominal pain, headaches, nausea, vomiting, skin rashes and mucous membrane irritation. In the long-term, these toxins can cause liver damage and be carcinogenic.

Blooms also negatively impact aquatic ecosystems. When algae die off and sink to the bottom of rivers and lakes, they consume oxygen in the bottom sediment layers. This decreases available oxygen for the survival of aquatic life. These low oxygen levels can also cause undesirable dissolved minerals such as iron and manganese to be released from sediment into the raw water source, which causes aesthetic challenges.

OCWA works closely with local health units and the Ministry to monitor the occurrence of algae blooms. We also work in partnership with our clients to pro-actively monitor and sample before and during bloom season.

The Governments of Ontario and Canada are looking at ways to reduce harmful algae blooms, The province has a 12-point Plan outlining how it is working with its partners to fight blooms in the Great Lakes and other water bodies. And earlier this year, Canada and Ontario released the Lake Erie Action Plan, which focuses on reducing nutrients such as phosphorous to receiving bodies that can promote algae growth.

As part of our commitment to providing safe, clean drinking water and protecting the environment, OCWA collaborates with institutions conducting cyanobacteria research. We are pleased to be supporting the work of two Natural Sciences and Engineering Research Council (NSERC) Chairs with the Universities of Toronto and Waterloo.

As a partner, OCWA receives regular updates on the latest research projects, including algae blooms in the Great Lakes. One of the projects we're involved in through the NSERC is an examination of the accumulation of algae at various stages of water treatment based on presence in the raw water source. OCWA is also pursuing collaborations with other Canadian and American research institutions that have extensive experience in handling the challenges of algae blooms.

For more information on blue-green algae, please visit the Ministry of the Environment, Conservation and Parks' website or contact your OCWA Operations Manager.