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The Water Security Agency (WSA) believes it has an answer about the odd, purple-blue water found by ice fishers in and on Pasqua Lake two weeks ago.
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The provincial water manager said in a media release test results show the discoloration was 鈥渃aused by a late cyanobacteria (algae) bloom last fall.鈥�
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Like what University of Regina (U of R) water scientist Dr. Peter Leavitt told the Leader-Post last week, researchers 鈥渂elieve the bloom froze in the ice in mid-October 2020 and underwent freeze and thawing cycles over the past few weeks,鈥� the WSA said. 鈥淐yanobacteria (algae) exposed to these conditions release a bright blue pigment called phycocyanin, as well as microcystin, a related toxin.鈥�
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Leavitt, who heads the U of R鈥檚 Institute of Environmental Change and Society, said the colour pigment is equivalent to 鈥渁n organic dye,鈥� not harmful to humans; it results from the freeze-thaw cycle busting up algae cells.
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He and the WSA agreed the amount of microcystin found in the purple-blue samples is not particularly toxic 鈥� 0.1 parts per billion, the WSA said in its release.
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The acceptable risk level, the WSA said, for 鈥渞ecreational activity is 20 parts per billion,鈥� and for drinking water is 鈥�1.5 parts per billion.鈥�
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Leavitt cautioned high levels of microscystin could be an issue: It鈥檚 a cancer-causing toxin that will attack an organism鈥檚 liver. Humans tend to pass it through their systems quickly, by ingesting algae-covered water. He suggested avoiding chronic exposure to it.
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鈥�(Microcysitn) is found in many if not all of the lakes of southern Saskatchewan, but at fairly modest levels.
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鈥淲hat we鈥檙e seeing is these blooms are becoming more toxic,鈥� because of global warming and increased nutrient run-off (phosphorus and nitrogen) from farmers鈥� fields, he said.
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The WSA is to continue studying Pasqua Lake into the spring to check how or if algae blooms there are choking off its oxygen.
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