Lichens and air quality in Grand Portage National Monument: Final Report.

Abstract

This study of the lichens of Grand Portage National Monument was designed to collect lichens for a lichen flora and for elemental analysis, to study the health and distributions of species most sensitive to air pollution, and to assess the air quality on the lichens. Six localities were studied, both near the shore of Lake Superior and on the Pigeon River. Samples of four species were collected and analyzed for element accumulations. The lichen flora was quite diverse for so small an area. There were 183 taxa of lichens present and numerous species very sensitive to sulfur dioxide. The distributions of the most sensitive species did not show patterns that would suggest air quality problems. The lichens studied by elemental analysis showed, in most cases, normal accumulations. The reason for the higher magnesium in three species at Fort Charlotte is unknown but the slightly elevated lead levels at Mt. Rose may be due to automobile traffic. Therefore, there seem to be no indications of air quality problems in the park now. Recommendations are for annual elemental analysis of lichens to detect any changes due to the reactivation of the power plant at Schroeder. A complete restudy of the lichen flora should be done every 3-5 years.