Agriculture student researches impact of mining on wild rice in Minnesota lakes

July 11, 2013
Giselle Varrientos

PLATTEVILLE, Wis. – What is causing the wild rice in Minnesota’s lakes to die?

Giselle Varrientos, a University of Wisconsin-Platteville junior soil and crop science major with an emphasis in plant breeding and genetics from Kenosha, Wis., is conducting research to try to find the answer.

The purpose of her research is to help reconstruct the history of the area surrounding Minnesota’s Bingwi Lake, also known as Little Sandy Lake, to determine what is causing the wild rice to die. Wild rice historically has been a major source of food for the Fond du Lac, Wis., Native American tribe.

Varrientos is under the mentorship of UW-Platteville geography professor Dr. J. Elmo Rawling III. The research project, which began in late March, is funded by the Wisconsin Alliance for Minority Participation and is being conducted in partnership with Dr. Amy Myrbo and her undergraduate research assistant, Stefanie Mayer, from LacCore, a laboratory facility in Minneapolis, Minn., that provides free or low-cost support for the collection and study of lake sediment cores. The facility is funded by the National Science Foundation and the University of Minnesota.

“When iron mining began, lakes like Bingwi Lake were a major source of rice for the Fond du Lac Native American tribe,” Varrientos stated. “Over time, the wild rice plants began dying. The research that Dr. Myrbo and Stefanie conducted examined sulfate levels in Minnesota lakes and how those levels impacted the content of organic matter. Tests conducted on more than 100 lakes and rivers across the state revealed high levels of sulfate, which can come from decaying plants and animals, but can also come from industrial processes and mining facilities. They noted that wild rice was not abundant in water with higher levels of sulfate.”

“My research is an extension of the work that they have done. By scientifically studying the history of the lakes, we hope to reconstruct the environmental changes that have had an impact on Bingwi Lake – especially changes associated with events such as climate change, human impact and other processes,” Varrientos continued. “We want to determine what is causing this ecosystem to die. Is the rice dying as a result of the effects of an industrial process or is it dying as a result of a natural phenomenon?”

Working in UW-Platteville’s Tree-Ring, Earth and Environmental Sciences laboratory, Varrientos has spent hours completing background reading and research as well as numbering and ordering samples taken from more than 300 samples from six different cores extracted from Lake Bingwi. Pre-treatment of the cores is the next step.

“Pre-treatment will begin in mid-July,” Varrientos stated. “Accurate readings of core samples can only be done if all organic materials are removed. We pre-treat the sediment by adding hydrochloric acid, hydrogen peroxide or nitric acid, which eliminates all organic materials, leaving pure sediment. We can then measure the percentages of sand, clay and silt with a laser diffraction particle-size analyzer.”

“By closely examining the different layers in the sediment, and then measuring the quantities of sand, silt and clay, we can reconstruct the lake’s history,” Varrientos said. “This will help us figure out what caused the wild rice plants to die and when that phenomenon began. Understanding what is causing the wild rice to die may give us insight into how to prevent it from happening in the future.”

She anticipates that pretreatment and data analysis will be completed by October.

“I am excited to be a part of this research,” Varrientos said. “As a student, this type of research keeps my hunger for knowledge alive and keeps me aware of current political and environmental issues. It also gives me the chance to meet intellectual people who have so much knowledge about these issues and are willing to share it.”

Written by: Laurie A. Hamer, communications specialist, College of Liberal Arts and Education, (608) 342-6191,


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