Blue-green algae are making a scene

Facts about algae in surface water 

Image of a poster showing cartoon algae enjoying the sunshine


What are the risks associated with blue-green algae in Alberta?

Where did this concern about blue-green algae come from?

Blue-green algae (cyanobacteria) produce toxins that are harmful to humans, livestock, pets, and wildlife, causing illness and, in rare cases, death. Blooms often produce a distinct taste and odour, and are a nuisance and health hazard for many ranchers, boaters, swimmers, and other surface water users. 

Given the disturbance algal blooms cause to water bodies, they are sometimes mistaken for an invasive species. Though blooms occur naturally they can have negative consequences on aquatic ecosystems, which are heightened as blooms get larger and become more frequent. 

When the mass of algae eventually dies, it decomposes, using up valuable dissolved oxygen and disrupting other natural processes. When dissolved oxygen is too low, fish and aquatic organisms may struggle to survive. 

Managing algal blooms is important for the entire aquatic ecosystem and for land based water users including livestock, wildlife, and humans. While problematic for water quality, algal blooms (including those due to blue-green algae) are a natural phenomenon in Alberta that is often accelerated by human induced factors.

What is the science behind blue-green algae (cyanobacteria) blooms?

Blue-green algae occur naturally in surface waters and there are more than 100 species in Alberta, ranging in size and shape. 

When optimum surface water conditions are reached, the organism can reproduce rapidly forming a “bloom.” Conditions that promote growth include warm temperatures, sunshine, slow-moving water, and high levels of nutrients. 

Not surprisingly, the most common time for algal blooms in Alberta is July to September when air temperatures are high, the sun is shining, and water levels are low.

While these conditions occur naturally during the summer, regardless of human interaction with the surface water, it is the unnatural loading of phosphorus into lakes that accelerates algal growth. 

Algal blooms have been linked to human presence ever since phosphorus addition to surface waters was identified as a key contributor to excessive algal growth. Phosphorus is an essential element for plant growth, and while it is found naturally in decaying organic matter, rocks, and soils, it is also a common ingredient (and is present in much greater concentrations) in fertilizer and household cleaning products. 

Runoff from urban and agricultural areas transports phosphorus from fields and soils to rivers and ponds, septic fields contribute effluent to shallow groundwater, and wastewater treatment plants in urban areas release treated wastewater into rivers. 

Nitrogen is another key nutrient found in wastewater and fertilizers and, once in the aquatic environment, further boosts the growth of aquatic plants including blue-green algae.   

What is being done about blue-green algae?

Blue-green algae are a natural part of the Bow River Basin ecosystem. Management goals are not focused on eradicating blooms completely, but rather limiting the excessive growth of unnatural blooms caused primarily by high phosphorus loading to water bodies from human activities. 

In the Bow River Basin, about 21% of phosphorous in the Bow River comes from point sources such as wastewater treatment plants, while non-point sources like stormwater runoff, irrigation, and stream bank erosion account for about 78% during open water season. Point sources can be more straightforward to manage than non-point sources, because it is easier to locate the source of loading, but this would only address a small part of the problem. Runoff and non-point sources typically involve far more people across a much greater spatial and temporal scale, but collectively these sources contribute the most phosphorus loading. Conversations about how to reduce phosphorus loading to rivers, and consequently reduce algal blooms, must include each of the many stakeholders to find a collective solution. 

To manage phosphorus loading to surface waters, Alberta Environment released an interim policy on effluent limits in 2008. Following this policy, Alberta Sustainable Resource Development brought together a diverse group of stakeholders to address phosphorus loadings in the Bow River, from point and non-point sources throughout the basin. Government and non-government representatives, both urban and rural, came together to develop the Bow River Phosphorus Management Plan released in 2014. The plan defines the issues and proposes strategies and actions for managing phosphorus in the Bow River. Through its implementation, this plan will create a model for other areas suffering from excessive phosphorus and troublesome algal blooms.

Additional measures taken by the Government of Canada include limits on phosphorus in laundry detergents, which have been in place for decades, as well as a 2011 ban on the use of phosphates (the problematic form of phosphorus) in dishwasher detergents. These measures help reduce phosphorus loading from municipal wastewater effluent point sources. Reduction of phosphorus in wastewater effluent, a point source in the river, is an ongoing area of research, and best practices continue to be updated and implemented whenever possible. However, non-point sources such as urban and agricultural runoff remain high in both phosphorus and nitrogen and continue to be major contributors to algal blooms across the country.

Short term chemical control of algae is prohibited and creates additional issues for natural lakes, so it is well accepted that longer term regional solutions to reduce nutrient loadings to surface water will be key for managing algal blooms. 

To minimize the risk to human health from direct exposure, Alberta Health Services posts active blue-green algae advisories online in addition to signage around lakes known to experience or be experiencing elevated levels of algal blooms. This helps protect lakeside visitors from potential exposure to the algae and their associated health impacts. 

What can I do about blue-green algae?

Limiting nutrients entering the water helps reduce the possibility of blue-green algae blooms. Reducing fertilizer use and using holding tanks instead of septic fields near lakes are some ways to minimize contributions to surface waters. 

Choosing cleaning products with lower phosphorus levels and avoiding the use of fertilizers on your lawn will also reduce the nutrient runoff to streams and rivers. 

Best management practices for agriculture and ranching operations are available through Alberta Agriculture, such as grassed waterways and buffer strips to manage nutrient loading to ponds and dugouts. 

When blue-green algae advisories are in effect, it is best to avoid all contact with the bloom. Wading and swimming in areas of a water body with blue-green algae could cause skin and eye irritation. Alberta Health Services recommends not eating fish from the lake or feeding it to pets. 

Drinking or cooking with water from the lake is not recommended, especially since boiling the water will not remove toxins produced by blue-green algae. If contact with a bloom occurs, showering with clean water as soon as possible can reduce effects of skin exposure. 

Sources and additional information

Alberta Environment and Parks. (n.d.). Cyanobacterial Blooms and Toxicity.

Alberta Environment & Sustainable Resource Development. (2014). Bow River Phosphorus Management Plan. Retrieved from 

Alberta Health Services. (n.d.). Frequently asked questions: Blue-green Algae (Cyanobacteria). Retrieved from 

Canada moves to cut phosphates to fight algae problem. (2008). Retrieved June 22, 2017, from 

Detergent change makes for dingy dishes. (2011). Retrieved June 22, 2017, Retrieved from

Elger, S. (2015). Blue-Green Algae (Cyanobacteria) in Surface Water Sources for Agricultural Usage. Retrieved from:$department/deptdocs.nsf/all/wqe15283/$file/blue-green-algae.pdf?OpenElement

Koning, C. W., Camm, E., & Kerr, J. (2017). Water Quality and Phosphorus. Bow River Phosphorus Management Plan.