Monitoring Algae Levels in the Clark Fork River

Abstract

In response to public concern over attached algae levels in the Clark Fork River that sometimes interfere with beneficial uses, a public-private consortium has developed a voluntary plan to reduce nutrient loads. A long term data base is needed to evaluate to what extent algae levels respond to changing nutrient loads in this river. To initiate such a data base, algal biomass was measured at 15 sites in the Clark Fork and compared to historic data. Recommendations are made for a long term monitoring plan and for criteria for algal levels. Algal levels exceeded the proposed criterion throughout the river in 1987 and in the upper river in 1995. Middle river algal levels were well below the criterion in 1995.