Hydrologic Change and Nutrient Cycling

Excess nitrogen and phosphorus contribute to harmful algal blooms and hypoxic conditions that threaten environmental, wildlife, and human health. Wetlands can filter excess nutrients, protecting vulnerable downstream ecosystems, and are considered sustainable solutions to water resource management. However, projected increases in the frequency of drought and extreme precipitation events associated with climate change will lead to more frequent sediment drying and re-flooding. When dried sediments rapidly re-flood, they often release nutrients, inhibiting a wetland’s ability to support biodiversity and improve water quality, two common goals of wetland creation, restoration, and management.

I am establishing a research program at Kent State University with the goals of:
1) characterizing hydrologic change associated with climate change and wetland management,
2) elucidating the biogeochemical mechanisms behind hydrology-influenced changes in nutrient cycling in order to
3) assess trade-offs associated with management scenarios, particularly for Great Lakes area ecosystems.    

Vulnerability of a Unique Microbial System to Environmental Change

The recent discovery of the staggering diversity of unculturable microorganisms presents challenges and opportunities to better understand the physiological mechanisms driving ecosystem functions. In Lake Huron near Alpena, MI, submerged karst features vent groundwater carrying ions from 400 million year old evaporites, establishing a high-conductance, high-sulfur, low-oxygen environment in which taxonomically and metabolically unique benthic microbial mats grow (link nature education paper). The sinkholes are located in an area subject to many stressors, including nutrient and contaminant pollution, and their valuable communities may be vulnerable to short and long-term disturbances associated with anthropogenic change. In collaboration with researchers at the University of Michigan, Grand Valley State University, NOAA's Great Lakes Environmental Research Lab (GLERL) and Thunder Bay National Marine Sanctuary, I am characterizing vertical stratification of microbial community structure and function across the sediment-water interface and into sediments in this unique system. 

Effects of Drying and Reflooding on Wetland Phosphorus Retention

Throughout most of America’s history, wetlands have been systematically drained and “reclaimed,” for agricultural use. In recent decades, the values of wetland ecosystems have been recognized, and many historically drained areas are now being re-flooded in wetland restoration projects. Re-flooding historically drained areas can have negative unintended consequences, particularly release of sediment phosphorus (P), which can establish eutrophic conditions and be exported to vulnerable downstream ecosystems. To better understand effects of altered hydrology on wetland sediment P release, I 1) monitored P dynamics in a restoration that entailed re-flooding a historically drained wetland and 2) experimentally desiccated and re-flooded sediments from biogeochemically diverse wetlands in the lab during my dissertation research in Steve Hamilton’s lab at Michigan State University's W.K. Kellogg Biological Station.
            In the wetland restoration, sediments released substantial amounts of P after reflooding, establishing eutrophic conditions throughout the wetland and exporting excess P to downstream ecosystems. Although the restored wetland released P, experimentally desiccating and re-flooding a more diverse array of sediments revealed that sediments display different rates of P flux after re-flooding, depending on their biogeochemical characteristics. Sediments that displayed the highest P release rates contained large amounts of easily mobilized P, reflecting a history of excess P loading (i.e., from anthropogenic fertilization) and disturbance. It is clear from my dissertation research that many sediments, especially those that have been historically drained and cultivated, are susceptible to P release, potentially limiting achievement of restoration goals. However, the rate of P release depends on biogeochemistry, and some ecosystems are more susceptible to P release than others. In general, it is important to weigh the risk of sediment P release against the potential benefits of wetland restoration when making management decisions.

Kinsman-Costello, L.E., J.M. O’Brien, and S.K. Hamilton. 2014. Re-flooding a historically drained wetland leads to rapid sediment phosphorus release. Ecosystems 17(4): 641-656. DOI: 10.1007/s10021-014-9748-6
O’Brien, J.M., S.K. Hamilton, L.E. Kinsman-Costello, J.T. Lennon, and N.E. Ostrom. 2011. Nitrogen transformations in a through-flow wetland revealed using whole-ecosystem pulsed 15N additions. Limnology & Oceanography 57(1): 221-234. 
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Phosphorus-fueled toxic algal bloom in western Lake Erie on August 4, 2014. NASA image courtesy Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team at NASA GSFC.
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Purple microbial "fingers" carpet the benthos in Lake Huron's Middle Island Sinkhole.
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A restored wetland in southwest Michigan rapidly released large amounts of phosphorus when historically drained sediments were re-flooded.
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The effects of experimental drying and re-flooding on sediment-water phosphorus flux depend on sediment biogeochemical characteristics.

Dissolved Organic Carbon in Freshwater Ecosystems
Dissolved organic carbon (DOC) plays many important roles in aquatic ecosystems, depending on the amount of DOC present and its chemical characteristics. As a researcher in Gary Lamberti’s lab at the University of Notre Dame, and with Paul Frost, James Larson, and others, I investigated the role of colored DOC in ultraviolet radiation attenuation in streams and the relationship of DOC quantity and quality to aquatic ecosystem biogeochemistry. This research was conducted in the Upper Peninsula of Michigan in and around the University of Notre Dame Environmental Research Center.

Frost, P.C., L.E. Kinsman, C.A. Johnston, and J.H. Larson. 2009. Watershed discharge modulates relationships between landscape components and nutrient ratios in stream seston. Ecology 90(6): 1631-1640.
Frost, P.C., J.H. Larson, L.E. Kinsman, G.A. Lamberti, and S.D. Bridgham. 2005. Attenuation of ultraviolet radiation in streams of northern Michigan. Journal of the North American Benthological Society 24: 246-255.