Algae's effect on water colour during the winter months
In March 2021, a mysterious phenomenon occurred on Pasqua Lake that had many citizens wondering and worrying about water quality in the lake. The Water Security Agency (WSA) acted quickly to sample the affected areas and teamed up with the University of Regina to investigate the source and cause of the colour. Analysis of the Blue Water event, as it became known, found that the blue-coloured water observed in and on the lake was a natural, harmless pigment called phycocyanin.
The phycocyanin originated in cells of decaying blue-green algae (cyanobacteria) that were trapped in the ice in the fall. When the blue-green algal cells burst, the phycocyanin pigment mixed with the melting ice giving the water a blue hue.
Algal toxin tests found that the water was non-toxic. In addition, phycocyanin, the pigment responsible for the blue colour, is not toxic. Measurable toxins associated with blue-green algae were well below federal guidelines for recreational use of water.
A picture showing blue pigment from a fall blue-green algal bloom that was frozen in the ice (left). The picture on the right shows blue coloured water in a hole augered through the ice. In this case the blue colour was from pigments released from algae, not the whole algae themselves. For those interested, a link to this paper is provided at the end of this article.
Source: Haig HA, AM Chegoonian, J-M Davies, D Bateson and PR Leavitt. 2022. Marked blue discolouration of late winter ice and water due to autumn blooms of cyanobacteria. Lake and Reservoir Management.
This is the first known report of under ice water turning blue as a result of pigments being released from a fall algal bloom frozen in ice. This event required a number of factors to co-occur and is still considered to be rare. While determined to be innocuous, it is possible that this event will recur in future years. There are many factors that affect lake water colour, but the primary ones are particles suspended or dissolved in water including algae, sediment, dissolved organic matter and minerals. As in other years, coloured ice or water is anticipated to be observed in various Saskatchewan lakes and waterways this winter.
Algal colour depends on light conditions, which affects the species of algae that can grow, their abundance, and the degree of pigment or light adaptation used by the algae. Common colours imparted by algae in lakes during the winter are golden or brownish in colour, the more common green to bluish-green colour, and pink to red and purplish.
The pinkish-red coloured water observed in Perch Lake during the winter of 2015 (see pictures above) was due to a species of Planktothrix, which is a type of blue-green alga. While the red/pink colouration is not as familiar as the summertime green or blue-green colours, it is a natural algae/pigment colour. The reddish coloured pigment is part of the alga’s adaptation to low light conditions and at times grows in sufficient amounts to cause noticeable colouration of the water/ice. Similar observations have been made at Fork Lake located approximately 100 west of Saskatchewan-Alberta border and at approximately the latitude of Meadow Lake Provincial Park. Planktothrix is known to produce algal toxins so care should be taken to ensure such waters are not consumed by people, pets or livestock until the water has been tested.
What do I do if I observe a bloom? Algal blooms are common in Saskatchewan and most people have become accustomed to observing them. It is critical for people to be aware that some blooms can produce toxins and individuals should use caution around blooms. While the risk of toxin production is highest during the summer and autumn, they can be produced at other times of the year, including in winter.
If a bloom appears atypical it may be helpful to document the bloom with pictures. Blooms can be reported on Saskatchewan Health’s “Report an Algal Bloom” webpage. For atypical looking blooms, individuals can also contact the Water Security Agency and discuss their observations with a water quality ecologist (866.727.5420).
The full peer-reviewed article on the blue water event can be accessed at the following link or QR code:
https://www.tandfonline.com/doi/full/10.1080/10402381.2021.1992544
