A 400-year phytolith-based reconstruction of wild rice (Zizania palustris) abundance from Mud Lake core sediments, Fond du Lac Band of Lake Superior Chippewa Reservation, Minnesota, USA.

Wednesday, 17 December 2014
Ricardo Munoz, University of California Santa Cruz - UCSC, Department of Earth and Planetary Sciences, Santa Cruz, CA, United States, Emilia Caylor, University of Houston Downtown - UHD, Department of Natural Sciences, Houston, TX, United States, Chad L Yost, University of Arizona, Department of Geosciences, Tucson, AZ, United States, Christa Drake, University of Minnesota Twin Cities - UMinn, Saint Anthony Falls Lab, Minneapolis, MN, United States, Jammi Lynn Ladwig, University of Minnesota Twin Cities - UMinn, Department of Anthropology, Minneapolis, MN, United States, Amy Myrbo, University of Minnesota Twin Cities, Continental Scientific Drilling Coordination Office, Minneapolis, MN, United States and Tom Howes, Fond du Lac Resource Management, Natural Resources, Cloquet, MN, United States; Fond du Lac Resource Management, Department of Natural Resources, Cloquet, MN, United States
Wild rice (Zizania palustris L.) is an aquatic grass with spiritual and subsistence significance to Native people of the Great Lakes region of North America. Mud Lake (Mashkiigwaagamaag), located on the Fond du Lac Band of Lake Superior Chippewa Reservation in Carlton County, Minnesota, USA, once supported an extensive population of wild rice (manoomin). However, early 20th century attempts to ditch and drain surrounding wetlands for landuse intensification severely altered the natural hydrological system that supports wild rice. Fond du Lac Resource Management (FDLRM) technicians are currently working to increase the wild rice population in Mud Lake. As part of these efforts, this phytolith study was undertaken to better understand how wild rice abundance has fluctuated over the past 400 years, with particular emphasis on the 19th and 20th centuries. Phytoliths are microscopic opal silica plant remains that are incorporated into soils and lake sediments after the plant-parts that contain them decay. Wild rice produces phytolith morphotypes that are unequivocally diagnostic. Mud Lake core MNMN-MUD11-1C-1P-1 (46°43'38.39"N, 92°42'2.45"W) was piston cored by LacCore (National Lacustrine Core Facility) and FDLRM technicians on 24 May 2011. Initial core descriptions, multi-sensor core logging, phytolith sampling and phytolith extractions were completed during the summer of 2014 at LacCore. Wild rice phytolith identification and quantification was conducted on twelve samples using brightfield microscopy at 400x magnification. Wild rice phytolith concentration values ranged from 68 to 2,300 phytoliths/cm3. Wild rice accumulation rates ranged from 9 to 383 phytoliths/ cm2/yr, peaking in 1952 AD. Wild rice abundance in Mud Lake appears to be influenced by a complex set of variables that include anthropogenic disturbance, climatic events and aquatic plant community succession.