Wednesday November 2, 2022
Idaho Department of Health and Welfare —
Each fall as the weather cools, the Department of Health and Welfare gets questions from anglers eager to cast lines in lakes or rivers where water quality warnings were made.
Water quality warnings are often because of detection of harmful cyanobacterial blooms (“harmful algal blooms”), caused by cyanobacteria and the toxins they can produce. Cyanobacterial blooms, which can be made worse by such things as nutrient pollution and warm water, can have public health, environmental, and economic effects.
As days shorten and the weather cools, it’s the final phase of the annual bloom season. Cyanobacteria populations are still present —but are beginning to decline. However, cyanobacteria do not disappear, and a portion of the bacteria will remain near the surface of a water body even when most of the population settles to the bottom.
Idahoans who love fishing, swimming, and dog walking should consider avoiding areas that were recently still blooming and keep pets away. The toxins the bacteria produce are not visible and may remain in the water after the bloom has vanished.