Blue Green Algae in the Coldest Deepest Lake in BC

In 2017 the bays on Quesnel Lake were pictures here with blue green algae. Interior Health was contacted - as many residents take their water from the lake and were concerned about the health and safety of their families and pets. Interior Health explained that they do not usually test a lake unless the Ministry of Environment requests that they test, and the Ministry has not reported any issues with the lake, When I wrote Interior Health and stated that in that case it must be safe to use the water, drink it, swim in it etc., They sent someone out to test the water.... We, the residents on the Lake received no report, no reassurance, no follow up! What caused the Blue Green Algea on the Coldest deepest lake in BC? vvvvvvvv