Dr. Stephanie Schmidt
Assistant Professor, Departments of Biology and Environmental Studies
Ph.D. in limnology and marinesScience at the University of Wisconsin, Madison
E-mail - schmidts@stolaf.edu
Phone - 507-786-3984
Office - Regents Hall 432
Classes - Ecological Principles, Biogeochemistry, Conservation Biology, Introduction to Environmental Studies
Research - My research uses food web approaches, biogeochemistry and stable isotope ecology to ask questions relating to ecological variation over time or across ecosystems. Given human disturbance of ecosystems worldwide, the study of how food webs and nutrient processing change temporally and spatially is becoming increasingly important. Stable isotope analysis (i.e. d13C, d15N, dD, and d18O) is used to characterize food webs and identify important processes involved in nutrient cycling across the landscape. The projects listed below include broad research questions that are I am currently pursuing.
Stable isotope analysis of aquatic food webs
Stable isotope analysis (d13C and d15N) is a useful tool for characterizing food web structure and new quantitative methods have emerged for comparing multiple food webs in time or space.
Historical food webs of North American Great Lakes
For my Ph.D. research, I used stable isotope analysis and museum-preserved specimens to reconstruct the historical food webs of the Great Lakes. Understanding how the food web structure of the Great Lakes has changed due to over-fishing and non-native species introductions can provide important insight into future management policies, including the reintroduction of extirpated native species. I plan to continue working in the Great Lakes, comparing contemporary food webs of native fishes in Lake Superior and Lake Nipigon to this historical analysis.
Land-use impacts on stream food webs and food web linkages
I am currently investigating aquatic food webs across a broad landscape-level in the Cannon River watershed (Minnesota). I am interested in how differences in land-use impact aquatic and riparian food webs, and how these differences also influence aquatic-terrestrial food web linkages. We are studying two sites within the watershed that differed in their land-use characteristics (cultivated vs. forested land-use). No ecosystem exists completely in isolation and there has been a shift in food web ecology to consider the importance of linkages across ecosystems. As such, future research on this project this spring will involve characterization of the terrestrial riparian food web and quantification of food web subsidies (using d13C and dD) across the aquatic-terrestrial ecosystem boundary.
Biogeochemistry of aquatic ecosystems
Aquatic ecosystems are important centers of nutrient processing, receiving inputs of nutrients from the surrounding landscape. Understanding nutrient processing in these systems will provide a better picture of the ecosystem services they provide.
Land-use impacts on stream biogeochemistry
Nutrient loading from agricultural practices often results in degraded water quality in aquatic ecosystems. Research last fall, spring and summer revealed differences in nitrate (NO3) concentrations in two subwatersheds (located in southern Minnesota) of varying land-use practices; patterns in NO3 also changed with season. Determining the exact cause of these trends is important for managers interested in improving water quality. We are continuing to monitor the seasonal biogeochemistry of these watersheds and are also fine-tuning the GIS analysis to help interpret our nutrient data.
Research on stream biogeochemistry led to another research project on tracking sources of nitrogen in streams. Stable isotope analysis (d15N and d18O) of nitrate can help us identify sources (nitrified fertilizer vs. septic/manure) of nitrogen and processes, such as denitrification, involved in nutrient transformations in the two subwatersheds. This research project involves collaboration with a watershed organization, the Cannon River Watershed Partnership (Northfield, MN), interested in targeting sources of nitrogen pollution in the watershed for future management efforts.
Carbon cycling in restored wetlands
Wetlands, while diverse ecosystems and important centers of ecosystem services, are also a source of the trace gas, methane (CH4), which is a powerful greenhouse gas. We need a better understanding of how methane is produced and consumed (by methanotrophic bacteria) if we are to assess the net benefits of wetland restoration efforts, and predict how wetland structure and function might respond to future environmental changes. Our objective in this work is to improve our understanding of these processes, both spatially and temporally, by using stable isotopes to investigate CH4 dynamics in wetland soils on the St. Olaf College campus. Furthermore, we are using d13C analysis of taxon-specific microbial phospholipid fatty acids (PLFAs) to measure rates of methane consumption and assess the role of microbial diversity in determining rates of this critical process.