Recent Projects

Historical and modern water quality in the Lake Minnetonka Watershed
Contemporary water quality and sediment cores were analyzed from 18 lakes and bays in the Lake Minnetonka watershed to compare measured modern water quality to historical (pre-European settlement) water quality as inferred from diatom remains in sediment cores. Results showed that both modern water quality and historical water quality were variable across the watershed. Bays with direct connection to the main body of Lake Minnetonka were shown to have mesotrophic water quality in historical and modern times, whereas upgradient bays and lakes tended to have eutrophic to hypertrophic modern conditions and meso- to eutrophic historical water quality. Funded by the Minnehaha Creek Watershed District. See Research Reports for a downloadable report.

Historical water quality in North-central Minnesota lakes
We used paleolimnological techniques to reconstruct the trophic and sedimentation history of five lakes (Winona, Big Sandy, 1st Crow Wing, Dixon, Margaret) in northcentral Minnesota that are impaired or considered at risk for impairment by excess nutrients. All lakes showed some ecological change in the last 200 years. Most lakes showed an increase in sedimentation rates and a shift in diatom communities in the late 1800s likely in response to wide scale logging in the region. Secondary shifts occurred in most lakes in the 1960s-1980s during times of landuse change such as installation of a WWTP or development around the lakes. Funded by Minnesota Pollution Control Agency. See Research Reports for a downloadable report.

Historical water quality on Grand Portage tribal lands
Sediment cores from Swamp and Trout (aka Speckled Trout) Lakes, located on tribal lands within the Grand Portage Indian Reservation, were analyzed for biogeochemical signals of historical environmental change to help set nutrient standards. Trout Lake is a clear, deep lake and contrasts Swamp Lake, which is a large, shallow, wild rice lake. Sediment accumulation rates increased in the early-mid 20th century in both lakes, likely in response to logging. Historical diatom communities and diatom-inferred TP levels in Swamp Lake and Trout Lake showed only small changes in the past 200 years, although Swamp Lake has been and remains a more productive system. Funded by USGS and the Grand Portage Band of Chippewa and USGS. See Research Reports for a downloadable report.

Demonstrating benefits of conservation grasslands on water quality
Conservation grasslands are agricultural lands, planted in grass or other perennial cover as part of state and federal programs to minimize crop overproduction, to create wildlife habitat, and to reduce soil erosion and nutrient loss that otherwise would pollute lakes and streams. The research aims to quantify whether there is a critical amount or placement of grassland needed to produce a measurable reduction in erosion. Because lakes tend to trap most of the sediment that enters them, the rate of lake-sediment accumulation is a measure of erosion in the contributing watershed. Lakes in western and southern Minnesota have been selected according to the amount of conservation grasslands in their watersheds. Sediment cores from these lakes are being analyzed for accumulation rates of both sediment and phosphorus to see if these rates correlate with changes in land use. Funding for this project is provided by the Legislative and Citizen Commission on Minnesota Resources (LCCMR).

Continuation of the long-term mercury cycling study at the Marcell Experimental Forest
This project builds on a long-term ecosystem-scale experiment in which sulfate deposition to a boreal wetland was increased in order to examine the synergistic effects of atmospheric sulfate and mercury on production and export of the bioaccumulative neurotoxin, methylmercury. Previous work established a whole-wetland irrigation system for amending sulfate deposition through simulated rainfall. Results from the first six years of the experiment showed a consistent increase in mercury concentration and export from the wetland following sulfate addition, although the response differed markedly depending on the season of application and preceding climatic conditions. The focus of the investigation now shifts to the recovery of the wetland from chronic sulfate enrichment and the ultimate reduction in methylmercury production with the cessation of sulfate addition. Three specific questions concerning the rate of the response will be addressed: (1) what is the fate of the added sulfate and how is it recycled and ultimately sequestered in the peat, (2) how do water-table fluctuations and climate variability affect sulfur cycling and mercury methylation, and (3) what causes the observed seasonal differences in methylmercury production (following sulfate additions)—temperature, availability of labile carbon, speciation of inorganic Hg?

Restoring habitat "For the Birds"
Populations of many grassland-nesting songbird species such as Eastern meadowlark, bobolink, and Henslow sparrow have declined significantly in the past few decades. Correspondingly, the habitat that these birds prefer for nesting has also decreased significantly over the last 50 years. This project, directed by Shawn Schottler in cooperation with Great River Greening and Standing Cedars Community Land Conservancy, restored old fields to prairie habitat, with the specific goal of creating and evaluating improved grassland habitat complexes for these species. Three separate plantings of native species have been planted on lands at Standing Cedars, overlooking the St. Croix south of Osceola, Wisconsin. Distinct seed mixes, using different species compositions, will create areas of differing "structures"—short to medium height prairie with high forb diversity; tall, dense forb-rich prairie; and short structure grass-dominated prairie. The importance of having high plant diversity in prairie reconstructions has gained acceptance; this project will demonstrate that structural diversity is equally important. Creating prairie with distinct structural difference (e.g. tall vs. short) is likely a key element in improving grassland songbird habitat. Locally-grown seed has been harvested in preparation for plantings in later 2008 and 2009, to create new structures "for the birds."

Sources of Suspended Sediment in Minnesota's Rivers
A series of projects is examining the sources of suspended sediment to rivers and streams in Minnesota's agricultural areas. Current projects involve studies of Lake Pepin on the Mississippi River, the South Fork of the Crow River, and Redwood and Seven Mile Creeks, and other tributaries to the Minnesota River. These projects use atmospherically-deposited radio isotypes to fingerprint eroding sediment sources, and compare these fingerprints to suspended sediments in rivers and lakes. Funded by and in collaboration with Minnesota Pollution Control Agency.