Monitoring and classifying trophic states of selected lakes in Yellowstone Park, USA

Miller, A.

This paper discusses the monitoring and management of 40 lakes in Yellowstone National Park, USA, and presents the updated trophic state classifications for these lakes. The paper also documents that monitoring methods and perspectives used in this study meet current acceptable practices. For selected lakes in Yellowstone Park, phosphorus, nitrogen, chlorophyll-a, and other lake characteristics are studied to identify lake behavior and classify the annual average trophic state of the lakes over the past 12 years. The four main trophic states are oligotrophic, mesotrophic, eutrophic & hypereutrophic. The greater the trophic state, the greater the level of eutrophication that has taken place. Eutrophication is the natural aging process of a lake as it progresses from clear and pristine water to more shallow, turbid, and nutrient rich water where plant life and algae are more abundant. Human interaction tends to speed up eutrophication by introducing accelerated loadings of nitrogen and phosphorus into aquatic systems. As lakes advance in the eutrophication process, water quality generally decreases. Four models are used to classify the trophic state of the lakes; Carlson Trophic State Index, Burns Trophic Level Index, and the Vollenweider and Larsen-Mercier Models. Simple models are commonly used where steady-state conditions and lake homogeneity are assumed. There is concern that natural processes and human activity on and around the Yellowstone Lakes are causing the water quality to decline. Objectives of this study are to identify possible areas of concern and develop a baseline to which future evaluations can be compared.

Monitoring and classifying trophic states of selected lakes in Yellowstone Park, USA

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