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Research Highlights

Nitrogen uptake and hydrologic connectivity in streams and flow-through wetlands

Human alterations of nutrient cycles have jeopardized the status of many water bodies.  Currently, there is a need to understand how individual water bodies- which range widely in shape, size, and hydrology- may contribute differentially to nutrient transport and transformation through river networks.  For example, wetlands can be important sites of nutrient cycling and organic matter settling, but the role of wetlands depends partly on internal hydrologic connections between nutrient sources and sinks.

 

Lakeshore residential development and largemouth bass growth: a cross-lakes comparison

As humans develop lake shorelines, several aspects of the terrestrial and aquatic habitats are altered, and these changes have potential effects that can ripple through aquatic food webs (Engel and Pederson 1998, Francis and Schindler 2009).  Modifications to habitat structures along with direct human impacts, such as increased angling effort with lakeshore residential development (NRC 1992), may drive changes in game fish ecology.

Drivers of gas flux from temperate lakes: Partitioning the energetic contributions of wind and convection in 42 lakes

Estimating the flux of carbon dioxide (CO2) from lakes is important for understanding the role of these ecosystems in regional and global carbon budgets.  The efflux of partially soluble gasses such as CO2 is controlled by near-surface turbulence.  Lakes receive turbulent inputs across the air-water interface via two primary mechanisms: wind shear and negative buoyancy flux (convective cooling).  We examined the relative importance of wind and convection in 42 temperate lakes from multiple countries that covered gradients in latitude, size, and water clarity.

Genetic diversity of cyanobacteria in four eutrophic lakes

We explore the genetic diversity of cyanobacteria in four eutrophic NTL core study lakes (Lakes Mendota, Monona, Kegonsa, and Wingra) using a culture-independent genetic method (Miller and McMahon 2011).  The goals of this study were to 1) describe the phylogeny of cyanobacteria in each lake, and 2) examine genotype richness and evenness as the determinants of cyanobacterial diversity.

 

Crytal Lake Mixing REU Experience

Ellen Heyn's Juday Fellowship at UW Trout Lake Station has given her the opportunity to explore the interface between her two chosen fields of study—journalism and environmental studies. As the outreach specialist for the Crystal Lake Mixing Project,she has worked to bridge the scientific community with the general public by creating meaningful relationships between the worlds of science, academia, and daily life in Wisconsin’s Northwoods.

Integrating surface waters into a regional carbon budget

Recent syntheses suggest that globally, about half of the annual net global carbon input from the atmosphere to terrestrial ecosystems is passed on to streams, lakes and rivers.  This flux is of great consequence to the global C cycle, but is currently very poorly constrained.  To address questions about carbon cycling and potential climate change feedbacks we gathered a collaborative team of researchers and constructed a carbon budget for the ~6400 km2 Northern Highlands lake district (NHLD), integrating lake, stream, wetland and forests into the same framework.  We used a combination of approaches including new field surveys in wetlands, tower-based CO2 flux measurements, modeling using NTL-LTER and other data, and published literature.  This is one of the first ever complete carbon budgets at a regional scale to incorporate aquatic ecosystems. ....

 

Climate Change Impacts on Wisconsin’s Water Resources

NTL-LTER is an active participant in the Wisconsin Initiative on Climate Change Impacts, a project that was initiated in the fall of 2007 to assess and anticipate the impact of climate change on Wisconsin’s natural resources, ecosystems and regions. The primary mission of WICCI is to evaluate risks and vulnerabilities in each of these areas and to develop strategies for adaptation that can be used in natural resource management, municipal decision making, economic development, public health, and other critical components of Wisconsin’s quality of life. WICCI is governed by a Science Council whose 22 members are chosen from an array of disciplines within the University of Wisconsin System, the Wisconsin Department of Natural Resources and other state and federal agencies, universities and institutions. The primary function of the Science Council is to organize and coordinate Working Groups that have the scientific expertise to assess climate change ....

 

Water clarity responses to carp reduction in shallow eutrophic Lake Wingra

Shallow fertile lakes characteristically are turbid with dense algae and few submersed macrophytes when benthivorous fish such as carp are overabundant.  These lake conditions often represent a “stable state” until benthivorous fish densities are reduced either by natural die-offs (e.g., winterkill) or through management efforts.  Many shallow lakes have been “restored” to a clear-water, aquatic macrophyte state by whole-lake carp eradications, but such chemical treatments are not always effective due to lake size or interconnecting waters.  And in urban settings, chemically eradicating fish is sometimes not even possible due to public opposition ....

 

Long-Term Modeling of Ice Cover and Thermal Structure in Lake Mendota

In the past century, the historical air temperature record suggests a warming trend in southern Wisconsin, particularly during winter and spring seasons.  These changes should in turn have multiple effects on area lakes, such as later freezing and earlier ice breakup, warmer epilimnetic temperature, earlier onset of thermal stratification, stronger temperature gradient across thermocline, change in thermocline depth, and prolonged stratification period.To determine the consequences of these climate changes on ice cover and thermal structure of Lake Mendota, long-term, 100-year (1911-2010) simulations were performed using the DYRESM-WQI model.  Results show later freezing (9.8 days/100yr), earlier ice breakup (10.8 days/100yr), and shorter ice duration ....

 

 

Spread of aquatic invasive species in the NHLD

Several of the NTL study lakes were invaded by exotic species in the 1980s and ‘90s, providing a unique opportunity to measure long-term change in response to biological invasions.  Yet as aquatic invasive species such as Eurasian watermilfoil, rainbow smelt, zebra mussel, and spiny water flea proceeded to spread to the many thousands of lakes in the region, it became apparent that a broader geographic focus was needed in order to understand the spread and impact of these species ....

 

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