Development of an Empirical Model for Predicting the Stream Invertebrate Fauna of the Greater Yellowstone Ecosystem

Authors(s): C. Hawkins and T. Simmons

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Publication Date: 0000-00-00

Type: progress report

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Abstract: Objectives The objectives of this study are to develop an accurate, sensitive, and ecologically meaningful method to assess the biological integrity of streams in the Greater Yellowstone Ecosystem (GYE). By collecting physical habitat data and benthic macroinvertebrate samples from a large number of relatively pristine streams, most of them located in Yellowstone and Grand Teton National Parks, we can use multivariate statistical methods to generate a mathematical model that predicts the macroinvertebrate species composition at a potentially impaired stream. Comparison of the expected species composition (based on modeling) with that actually found at such a stream allows us to draw inferences about the biological integrity of the stream. The GYE is the largest relatively intact ecosystem remaining in the lower 48, but is under considerable pressure from urbanization, as well as traditional resource based industries. The bioassessment tool we are developing will allow us to determine the degree to which these activities are negatively impacting aquatic resources in the GYE. Findings and Status Thus far, we have collected data from 47 streams and rivers in Yellowstone National Park, 8 streams in Grand Teton National Park, as well as over 50 streams in the GYE outside the Parks. We have used these data to build a multivariate predictive model that accurately predicts the benthic invertebrate fauna of GYE streams. We assessed the accuracy of the prediction by measuring the ratio of observed (O) to expected (E) taxa (O/E score) at relatively pristine sites. The mean value of O/E for reference sites is 1.0, as would be expected if the model performs correctly. The standard deviation (SD) of the reference site O/E scores is a measure of model error. For our model, the SD of O/E scores is 0.128, which is quite good for these kinds of models. We are in the process of using the model to assess the biological integrity of 19 "test" streams in the GYE that are potentially impacted. The results of these analyses will help us to determine which land use activities may be having the greatest impact on aquatic resources in the GYE. In addition, we will be using these data to assess whether changes in stream biodiversity are adversely affecting stream ecosystem processes in an upcoming phase of the project.

Keywords: Greater Yellowstone Ecosystem, Grand Teton National Park, Yellowstone National Park, animal, habitat, invertebrate, human activity, suburban area, Bridger-Teton National Forest, Targhee National Forest, management