Trophic State Evaluation for Selected Lakes in Yellowstone National Park

Abstract

The purpose of this study was to tentatively classify the trophic level for selected lakes, except Yellowstone Lake, in Yellowstone National Park. This paper also documents the monitoring methods and perspectives used in this study as meeting current acceptable practice. For selected lakes in Yellowstone National Park, phosphorus, nitrogen, chlorophyll-a, and other lake characteristics were studied to identify short­term lake behavior and to classify the annual average trophic state of the lakes. By studying short-term lake behavior, there may be a greater understanding of how the trophic state of a lake can be averaged annually. Both the annual average trophic state and short-term lake behavior may help to understand the longer term trophic state of a lake. There is concern that natural processes and human activity on and around the lakes are causing the water quality to decline. We were unable to find any previous studies that defined the trophic state of the lakes. Therefore, an objective of this study is to evaluate the current trophic state of the lakes and develop a preliminary baseline to which future evaluations can be compared. This study has provided a benchmark trophic state survey not only for comparison to future evaluations, but to identify possible areas of concern. The greater the trophic state, the greater the level of eutrophication that has taken place. As lakes advance in the eutrophication process, water quality generally decreases.