A PALEOLIMNOLOGY STUDY OF HISTORICAL WILD RICE (ZIZANIA PALUSTRIS) IN LAC VIEUX DESERT, MI

Lac Vieux Desert is a freshwater lake located along the border of northern Michigan and Wisconsin. The lake once supported thriving stands of wild rice (Zizania palustris), an economically important and culturally significant emergent aquatic plant for the Lac Vieux Desert Ojibwe community, but wild rice coverage and densities are now greatly diminished. The objective of this study is to understand how changes in lake conditions may have impacted the wild rice population. To understand this change, a transect of three cores were recovered by the U.S Army Corps of Engineers to be analyzed for pollen, phytoliths, and diatoms. For this study, we collected subsamples continuously at 1-cm (~ 10yr) intervals to determine the abundance and composition of diatom assemblages from the early 1800s to present day. Since diatoms are ecological indicators, a change in the abundance of a species observed in assemblages overtime relays a change in the past lake environments. At approximately 7-cm from the top of the core, (~70 years ago), there was an increase in the abundance of the benthic species Geissleria acceptata. G. acceptata is common in environments of moderate to high ionic strength, which suggests a rise in lake salinity. From 0 to 11-cm from the top (present to ~110 years ago) Staurosira construens and Staurosira venter are abundant. S. construens and S. venter thrive in benthic and planktonic environments with elevated alkalinity. The abundance of these three species indicates an increase in the water depth of Lac Vieux Desert since ~1950, when the earliest dam was constructed. Samples after ~1950 occasionally contained spikes in charcoal, which may be related to logging and increased human activity surrounding the lake. Overall, from the present to 1950, Lac Vieux Desert transitions from being more abundant in benthic species to becoming more tychoplantonic, indicating an increase in water level during this time span.