Miller and Snow: Trophic Classification of Selected Lakes in Yellowstone National

TROPHIC CLASSIFICATION OF SELECTED LAKES IN YELLOWSTONE NATIONAL PARK +

A. WOODRUFF MILLER+ DAVID H. SNOW CIVIL & ENVIRONMENTAL ENGINEERING BRIGHAM YOUNG UNIVERSITY + PROVO + UT

+ EXECUTIVE SUMMARY coefficient. (See the Models section of the complete report for further explanations.) The purpose of this study is to evaluate the trophic state of five lakes in southern Yellowstone As would be expected, the trophic state of National Park in order to detennine if the human the lakes varied from month to month. Generally the activity in the local area is having a negative lakes bordered between the oligotrophic and environmental impact and possibly increasing the mesotrophic states. is classified as eutrophication rate. While some previous analyses slightly oligotrophic while and Heart have been done on these lakes, this study is intended Lake are classified as slightly mesotrophic. Riddle to be a preliminary trophic state evaluation to which Lake is classified as mesotrophic and Duck Lake future analyses can be compared. borders on the slightly oligotrophic and slightly mesotrophic state classification. The results are The five lakes sampled are Shoshone Lake, summarized in the table given below. Lewis Lake, , Riddle Lake, and Duck Lake. Each lake, with the exceptions of Riddle Lake Nitrogen was also measured in the samples and Duck Lake, was sampled at several locations. so as to detennine the nitrogen-phosphorus ratio (N :P These samples were taken during the months of June ratio) in the lakes. This was done to detennine if through August of 1999 by Woodruff Miller and nitrogen or phosphorus was the limiting nutrient in Dave Anderson of the BYU Civil & Environmental algal growth. Every sample from all five lakes is Engineering Department. phosphorus limited except the August sample of Shoshone Lake at DeLacy Creek (northeast side) and The Carlson Trophic State Index, the the July sample of Lewis Lake at Vollenweider Model, and the Larsen-Mercier Model (middle north side). were used to determine the trophic state of the lakes at each sampling location. The laboratory results This trophic state evaluation is meant to be a were plotted on the applicable model. The Carlson preliminary study to which future studies can be Model requires measurements of the total phosphorus compared. Further sampling of the lakes and concentration, total chlorophyll-a concentration, and tributaries at different times and different locations transparency. The Vollenweider Model requires the will be necessary in the future. Complete 40 page total inflowing phosphorus concentration and the reports of these trophic state classifications have been hydraulic residence time. Finally, the Larsen­ sent to the Yellowstone Center for Resources at Mercier Model utilizes the mean inflowing Mammoth and to the Snake Ranger District at the phosphorus concentration and a phosphorus retention South Entrance.

Published by Scholars Repository, 1999 1 142 University of Wyoming National Park Service Research Center Annual Report, Vol. 23 [1999], Art. 11

The chlorophyll-a analyses were conducted analyses of the samples. Finally, we appreciate the at the Pacific Northwest Regional Laboratories of the interest and fmancial contribution from the Bureau of Reclamation in Boise, Idaho. We wish to Yellowstone Center for Resources who partially express our thanks to them for their gratuitous work supported this research project in conjunction with and contribution to this project. We also wish to the Brigham Young University Civil and thank the Utah State Health Department, Division of Environmental Engineering Department. Laboratory Services for partially supporting the

Summary of Trophic Classifications of Sampling Sites Location Classification Shoshone Lake DeLacy Creek (Northeast Side) Meso trophic Shoshone Creek (West Side) Slightly Oligotrophic Near Outlet (Southeast Side) Border of Oligotrophic & Mesotrophic Shoshone Lake Average Slightly Oligotrophic Lewis Lake Dogshead Creek (Northeast Side) Meso trophic Lewis River (Middle North Side) Slightly Mesotrophic Boat Dock Near Outlet (South Side) Border of Oligotrophic & Mesotrophic Lewis Lake Average Slightly Mesotrophic Heart Lake Witch Creek (Northwest Side) Slightly Oligotrophic Witch Creek (Southwest Side) Slightly Mesotrophic Heart Lake Average Slightly Mesotrophic Riddle Lake North Side Mesotrophic Duck Lake East Side Border of Oligotrophic & Mesotrophic

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