Blue-Green Algal Bloom Underway in Northern Arm of Hayden Lake

Our water quality and biotic community monitoring expert is predicting the algal scum buildup that is typical of the late stages of an algal bloom to occur in the next couple weeks. The bloom result should be experienced in the northern arm of the lake but winds could drive the scum elsewhere. The prediction is based on water quality samples collected as part of the Hayden Lake Watershed Improvement District’s monitoring of the lake. Water quality samples collected a foot and a half deep in the waters near Sportsmans Access indicate a buildup of the blue-green algae, Anabaena. This blue-green is of particular concern, because some species produce a toxin. The Department of Environmental Quality has been informed and may issue warnings dependent on the Anabaena species concerned.

The District’s monitoring is specifically designed to detect the early signs of such blooms so these may be addressed by simple chemical additions. Blue-green algal blooms occur in the more phosphorous rich northern arm of the lake during low runoff years like we are experiencing. The low runoff deprives the lake’s waters of the plant growth nutrient, nitrate. The blue-green algal species are capable of fixing atmospheric nitrogen. With all the other nutrient resources left to the blue greens alone these species multiply rapidly into what is referred to as a bloom. A simple small nitrate addition to these waters of the lake can pre-empt this condition maintaining balance in the algal planktonic communities. Unfortunately, the District is just in the process of developing the water quality data base to justify such nitrate additions to DEQ and EPA. These measures cannot be employed this year, but with long term monitoring of the chemical and biotic condition of the lake we hope to manage such incidents in the future.