Nicolas Buer

Date of Award

January 2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Philip Gerla

Abstract

A degraded wetland with a history of human-induced hydrologic alterations lies within northwestern Minnesota's Skull Lake Wildlife Management Area (WMA). Although conservation practices have been enacted by the Minnesota Department of Natural Resources (MNDNR), there remains interest in the wetland's potential for ecological restoration. Restoration should not be undertaken without an understanding of underlying factors leading to degradation. A paired study between the disturbed wetland at Skull Lake WMA and the relatively natural wetland in the nearby Caribou WMA was designed to help understand near surface pore water geochemistry in an effort to determine causes of degradation and the potential for reversal. Shallow groundwater samples collected along and perpendicular to a major ditch flowing through the wetland were analyzed for pH, Eh, sulfide (H2S), soluble reactive phosphorus (SRP), sulfate (SO4), nitrate (NO3), and nitrite (NO2). Data revealed nutrient gradients and characterized nutrient transport relative to State Ditch 84. Wetland geochemistry comparisons between the disturbed cattail marsh and undisturbed sedge meadow showed increased concentrations of SRP, Eh, and pH. This indicates that Caribou WMA is a low nutrient ecosystem and suggests that Skull Lake WMA has become a phosphorus sink. Correlation between distance to State Ditch 84 and geochemical constituents indicated increased acidity and nitrite concentrations and possible SRP export out of the system during the fall. Ecological restoration through prescribed burning and water level control

may reduce invasive macrophyte communities, but altered pore water chemistry and increased pore water SRP concentrations may inhibit the full restoration potential of Skull Lake WMAs wetland.

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