How are blue-green algae blooms in Alberta impacted by precipitation and temperature changes?

Project Summary

Blue-green algae blooms, or cyanobacteria, are a common occurrence during the summer months in Alberta. These algae blooms consist of naturally occurring cyanobacteria that become more abundant in slow-moving, shallow, warm water, which are the summer conditions of many Alberta lakes. The presence of the cyanobacteria is natural; however, with climate change impacting precipitation and temperature, and land-use intensification changing across the province, the occurrence of blue-green algae blooms is also changing. These blooms pose a threat to humans as they have potentially toxic impacts if consumed or contacted. Quantifying the impact that climate change poses on algae blooms will help inform future decisions surrounding health advisories and the commonality of these occurrences. This study aims to determine any links between climate change and blue-green algae blooms in and across Alberta to help predict the future trajectory of blooms and to help bring awareness to one of the many local impacts of climate change.

Data for blue-green algae blooms (or lack thereof) was obtained for 136 lakes across Alberta from 2009-2023, along with extrapolated climate data for the township the lakes were located in from 2010-2023. Five measurements of cyanobacteria were considered: total cyanobacterial cell count, Microcystin, Microcystis mcyE, Anabaena mcyE, and Planktothrix mcyE. The focus of the study was on the average total cyanobacterial cell count across ecoregions. This data was pooled together by natural ecoregions found in Alberta (Boreal, Foothills, Grassland, Parkland) to determine general trends across the province. Climate data considered included the annual average maximum and minimum temperatures; total annual precipitation received; and the modeled snow water equivalent for the year.

With the above-mentioned data, it was determined that temperatures (average maximum and average minimum temperatures) and precipitation (Snow water equivalent and precipitation) are changing, but they cannot be directly linked to an impact on blue-green algae blooms. There was a different response seen across Alberta ecoregions, which is important to recognize, with large interannual variations in all measurements. For cyanobacteria, there was also no direct trend found, with variations seen within and across ecoregions. Analyzing the climate variables to the changes in algae blooms illustrates how each ecoregion has a different response based on the changes to precipitation and temperature. Precipitation increases led to increases in algae blooms in the Boreal and Parkland ecoregions and decreases in the Foothills and Grassland ecoregions. SWE increases led to an increase in algae blooms in the Parkland ecoregion, little to no impact in both the Boreal and Foothills, and a decrease in the Grassland. Temperature follows the same trend for both maximum and minimum, with a positive relationship seen between temperature increases and cyanobacteria increases in the Foothills and Grassland ecoregions, with the opposite being seen in the Boreal and Parkland ecoregions. All climate variables were found to be weakly or have a negligible correlation to cyanobacterial growth, with maximum temperature having the greatest impact out of the variables considered.

Image 1. Anabaena sp., a common genus of cyanobacteria in Alberta1.

Keeping this in mind, it is essential to understand how precipitation and temperature are impacting the occurrence of these events to have better information for the public surrounding the potential trends in algae blooms and the impacts that climate change may have on the persistence of these events in coming years. This is a concern for many people as it impacts recreation, health of people and their pets, and the aesthetics of Alberta's lakes.

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