Research – Current Projects

North Temperate Lakes Long Term Ecological Research (NTL-LTER)

NTL-LTER is a collaborative, interdisciplinary program studying the patterns and causes of long-term change in lakes and their landscape. Current NTL-LTER related activities within our group focus on unionid mussel population dynamics and responses to environmental stressors (Vince Butitta), examination of greenhouse gas dynamics in lakes and streams (Adam Rexroade and Emily Stanley), understanding spatial dynamics in NTL-LTER lakes (for more information, see below), and lots of other collaborative investigations.

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Continental Limnology Group

Inland waters are hotspots for storage and transformation of nitrogen (N), phosphorus (P), and carbon (C), and despite their limited spatial extent, these ecosystems make significant contributions to regional, continental, and global cycles of these elements. However, this understanding is largely based on extrapolating site-level measurements to the larger population of unsampled sites—an estimation method that usually includes substantial uncertainty. The overarching goal for this project is to address key challenges associated with extrapolation, and understand and predict nutrient patterns for ALL continental US lakes to inform estimates of lake contributions to continental and global cycles of N, P, and C. Our approach to this ambitious goal will be first, to build a large, integrated database of all lakes in the continental US (LAGOS-US) that includes measures of in situ nutrients collected from tens of thousands of lakes, and ecological-context metrics calculated for all ~130,000 continental lakes. Second, we will use this resource to address 5 central questions:

  • What are the spatial patterns of lake conditions and their ecological contexts at regional to continental scales?
  • How does consideration of lake nutrients as linked biogeochemical cycles improve prediction at continental scales?
  • Which variables are most responsible for the cross-scale interactions that influence lake nutrients at continental scales?
  • How is uncertainty in continental-scale extrapolation of lake nutrients influenced by novelty among ecosystems and ecological context?
  • How are estimates of continental lake nutrients influenced by propagating prediction uncertainties resulting from interactions, nonlinearities, and novelty?

Addressing these questions will require new tools and approaches, so our group emphasizes active collaborations among limnologists, statisticians, and computer scientists.

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Lake density across the continental U.S. Graphic from Winslow et al. 2014. Original data set for mapping from the USGS National Hydrography dataset.
Lake density across the continental U.S. Graphic from Winslow et al. 2014. Original data set for mapping from the USGS National Hydrography dataset.


Left-John Crawford and Luke Loken FLAMe-ing on Lake Mendota. The water intake structure can be seen attached to the back of the boat behind Luke’s shoulder. Photo: Nora Casson. Right: a FLAMe generated map of surface water dissovleved in oxygen percent saturation of Trout Lake. Graphic: Luke Loken

Understanding spatial dynamics of lakes: FLAMe studies

Maps are fundamental to our understanding of the world around us, yet for aquatic scientists, the opportunity to see spatial patterns within individual lakes and rivers is extremely limited. Their small size means these ecosystems are often poorly resolved by most remote sensing tools. And even when airborne devices can be tuned to the size of a lake or river, they quantify only a few water quality attributes on cloud-free days.

To overcome these limitations, we use automated environmental sensors to measure multiple water chemistry/quality variables across river and lake surfaces. The Fast Limnology Automated Measurement (FLAMe) platform, developed by John Crawford, Luke Loken, and colleagues (Crawford et al. 2015), was the result of a collaboration between USGS and NTL-LTER, and then improved with support from a UW2020 award. This platform allows us to see spatial patterns in aquatic systems, and ask questions about these patterns, how they change over time, and how they affect and are affected by other ecosystem processes. Luke Loken’s dissertation considered causes and consequences of spatial heterogeneity in both rivers and lakes, and Paul Schramm used the FLAMe to investigate spatial patterns of light extinction within lakes, and how and why the amount of within-lake variation differs among lakes.

We are now using the FLAMe to ask questions about rapid environmental change. Many ecosystem regime shifts involve transition in spatial patterns leading to the central question of this project: How does spatial pattern change for ecosystems near a threshold, and can spatial statistics indicate loss of resilience? This collaborative project with Mike Pace and Steve Carpenter and the Cascade Project considers the potential for spatial statistics to measure loss of resilience by studying lakes near and far from thresholds for harmful algal blooms (HABs) and David Ortiz is examining spatial patterns in algal blooms and metabolism for this project.

Please visit the FLAMe website for more information and find out where the FLAMe has been!

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Metabolism and methane of streams and rivers

Streams and rivers receive, transport, and transform carbon as water moves from terrestrial to marine environments, and collectively, these ecosystems make larger than expected contributions to global carbon gas emissions. These gases are derived from the surrounding environment and/or generated in situ via various respiratory pathways.  We are investigating patterns of stream metabolism and possible connections between metabolism and carbon gas effluxes- particularly methane emissions.

The StreamPulse project seeks to document patterns of primary production and respiration in streams and understand the mechanisms that shape these fundamental ecosystem processes, both locally and at a continental scale. This is a collaborative effort, with research hubs in Arizona, Florida, Montana, North Carolina and affiliated project partners in Connecticut, Sweden, and Switzerland. Here in Wisconsin where we are studying streams draining agricultural watersheds. Sam Blackburn’s master’s research examined how CO2 and CH4 emissions responded to flooding in several agricultural streams. We are continuing to study patterns and controls on these gases in Wisconsin streams and with collaborators in the U.S., China, and Sweden.

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