Pasqua Lake Blue Water Formations Show Evidence of Cyanobacteria Blooms, Lab Testing Finds
March 19, 2020 — A Water Security Agency preliminary analysis of the deep blue water formations found on Pasqua Lake (map attached of areas tested) indicate evidence of a biological phenomenon likely caused by a late cyanobacteria bloom last fall.
WSA, in conjunction with specialists from the lab operated by Dr. Peter Leavitt, Director of the Institute of Environmental Change and Society at the University of Regina, examined the sample. They believe the bloom froze in the ice in mid-October 2020 and underwent freeze and thawing cycles over the past few weeks. Cyanobacteria exposed to these conditions release a bright blue pigment called phycocyanin, as well as microcystin, a related toxin.
Further lab testing, in cooperation with the provincial lab, confirmed that microcystin levels were very low at 0.1 parts per billion (ppb) in samples. This is well below the acceptable risk level of 20 ppb for recreational activity and below 1.5 ppb for the Canadian Treated Drinking Water Guidelines. However, even with the very low toxicity level, citizens are advised to ensure pets do not drink the water at this time.
While the formation will dissipate and decay when winter ice leaves the lake, WSA will be increasing its monitoring through the spring season to see if decaying algal bloom is reducing oxygen levels in the lake. WSA has also been alerted to other potential areas of blue ice on the Qu’Appelle River system. This system is known to have high levels of natural occurring algal development that pre-date human activity in the area.
WSA employees began collecting water samples last Friday from the formation, which spanned an area of approximately 300 meters by up to 100 meters, after local area residents and fishers first noticed them.
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