Development of the catchment of the St. Louis River Estuary (SLRE) since Euro-American settlement resulted in quantifiable impacts to the aquatic ecosystem. Zizania palustris L. (northern wild rice) is an important food commodity for the state of Minnesota and the SLRE contains several wild rice stands. Known threats to SLRE wild rice stands include excessive sediment and nutrient loading. This paleoecological study combined pollen and phytolith analyses from five sediment cores from the SLRE to investigate three objectives: (1) enhance identification procedures by distinguishing Z. palustris pollen from other aquatic and upland grasses present in the fossil record; (2) reconstruct the 250-year history of upland and aquatic plants with a particular focus on wild rice; and (3) establish the utility of these indicators for paleolimnology studies of plant communities in a lotic system. Pollen and phytolith analyses of sediment samples yielded paleo-environmental data that confirmed that wild rice microfossils can be conclusively identified from sedimentary records and that Z. palustris was continuously present in the SLRE since the mid-1700s. Although our core sites were not ideally situated for assessment of wild rice history, we documented reorganization of Zizania stands apparently associated with shifts in water level. We recommend that retrospective studies for wild rice be based on sediment collected within or closer to littoral environments that support wild rice stands.
Bibliographical noteFunding Information:
Two grants supported this work. This work is the result of research sponsored by the Minnesota Sea Grant College Program supported by the NOAA office of Sea Grant, U.S. Department of Commerce, under grant No. R/CE-05-14. The U.S. Government is authorized to reproduce and distribute reprints for government purposes, notwithstanding any copyright notation that may appear hereon. Project funding was also made available by a contract with the Minnesota Pollution Control Agency through US EPA grant #00E05302 and support from the Minnesota Clean Water Legacy Amendment. The authors greatly appreciate the field assistance of Kitty Kennedy (NRRI), Lisa Estepp (NRRI), Meagan Aliff (NRRI), Carol Reschke (NRRI), Diane Desotelle (MPCA) and Fond du Lac Band of Lake Superior Chippewa Resource Management (FDLRM) technicians Charlie Nahgahnub and Cord Timo, and program manager Tom Howes. We thank Kelly Edwards and Dulcinea Groff, University of Maine School of Biology and Ecology, for providing time, equipment and expertise to produce SEM images. Personnel at LacCore (National Lacustrine Core Facility, University of Minnesota) supported phytolith and pollen sample preparations. Reviews by George Jacobson and two anonymous reviewers improved the manuscript. Publication of this work creates no conflict of interest for the authors.
- St. Louis River Estuary
- Wild rice