Using Diatoms to Reconstruct a Healthy Growing Environment for Wild Rice (Zizania palustris) in Northern Minnesota

Diatoms are  aquatic organisms, using them to analyze the history of a lake can provide essential information on lake chemistry, nutrient availability, and ecosystem succession. Sediment cores were taken from three lakes, Dead Fish, Perch and Rice Portage located in northeastern Minnesota on the Fond Du Lac Band of Lake Superior Chippewa Reservation. Subsamples were taken from the sediment cores and processed for diatoms, phytoliths, pollen and macrofossils.  The focus of this study is to provide a lake level reconstruction of trophic state and habitat changes over the period of transition to benthic-dominated diatom communities ~3000-1000 years ago. Changes in diatom species assemblages were analyzed to provide a baseline profile of lake depth and clarify the transition from planktonic to a highly benthic-dominated diatom community.  Phytolith, pollen, macrofossil, and lake sediment geochemistry were also analyzed to provide further evidence of the change in lake level, increased sedimentation rate, and terrestrial ecosystem change between 1000-3000 years ago. Wild rice is an important link to the past in the Chippewa culture, as well as a food source. In recent years, the lakes that have historically produced an abundance of wild rice have declined. The reasons for the decline are unknown, however, anthropologic land use change in close proximity to these lakes and diminishing water quality are believed to play a major role in this decline. This study will help us better understand how the productivity of the lake and the abundance of wild rice is linked to changes in the diatom communities.