Blue-Green Algal Blooms in Brownlee Reservoir

Document Type

Student Presentation

Presentation Date

April 2017

Faculty Sponsor

Shauna Anderson


In July 29, 2016, the Southwest District Health in conjunction with the Idaho Department of Environmental Quality, issued a health alert warning the public to avoid direct contact with the waters of Brownlee Reservoir (Southwest District Health, 2016). Over the summer, this specific reservoir, and others throughout the Snake River, had developed high concentrations of blue green algae, also known as cyanobacteria, which can be harmful to the waterbody’s ecosystem as well as animal and human health (Southwest District Health, 2016).

Such algal blooms are a natural phenomenon, but their severity can be exacerbated by many factors including anthropogenic influence. The National Lakes Assessment of 2012 has shown a nationwide increase in lake cyanobacterial concentrations of 8.3% between 2007 and 2012 (Environmental Protection Agency, 2012). This increase in cyanobacteria is positively correlated with the intensity of agricultural land use in surrounding areas (Carney, 2009). These findings suggest that the runoff of fertilizers from agricultural lands may spur the rapid and unnatural growth of cyanobacteria. The nitrogen and phosphorous present in fertilizers is already known to encourage bacterial and algal growth (Center for Earth and Environmental Science).

My study focuses on uncovering the primary factors which may have led to the 2016 cyanobacterial bloom in Brownlee Reservoir. Much of the land up river from Brownlee is dedicated to agriculture, indicating one of the causes of the algal blooms was likely agricultural runoff. However, because this study seeks explanations for past events, it is important to keep in mind that any results produced can never indicate causation, but only suggest possible links between phenomena.

First, I began by studying cyanobacteria, its specific lifecycle and needs. I then proceeded to research the factors that lead to its growth. I also studied nationwide trends in algal growth, since these may give insight into the factors that led to the blooms in Brownlee. Lastly, I studied the environmental trends in the regions surrounding regions, including weather trends.

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