Luke Loken is a Hydrologist with the Upper Midwest Water Science Center.
I am a hydrologist with the U.S. Geological Survey with a broad ecological background. My research focuses on hydrology and biogeochemistry in aquatic ecosystems at a range of ecological-scales. Some topics include: 1) The causes and consequences of spatial heterogeneity of water chemistry in lakes, rivers, and estuaries. 2) Drivers and patterns of ecosystem processes (metabolism, nutrient cycling, population dynamics). 3) The persistence of human-derived material (fertilizers, pesticides, chemicals) in river networks across landscapes.
Education and Certifications
Ph.D., Freshwater and Marine Sciences, University of Wisconsin-Madison, 2018
M.S., Freshwater and Marine Sciences, University of Wisconsin-Madison, 2014
B.S., Biology, University of Michigan, 2006
Affiliations and Memberships*
Center for Limnology (CFL) Affiliate
The Long-Term Ecological Research Network (LTER)
American Geophysical Union (AGU)
Association for the Sciences of Limnology and Oceanography (ASLO)
Society of Freshwater Sciences (SFS)
Science and Products
Below are data associated with this staff profile.
Pesticides and pesticide transformation product data from passive samplers deployed in 15 Great Lakes tributaries, 2016
This dataset includes pesticides and pesticide transformation products in 15 tributaries of the Great Lakes. Pesticides were monitored using polar organic chemical integrative samplers (POCIS) to estimate concentrations in water following standard protocols (Alvarez, 2010) in June and July 2016. POCIS extracts were analyzed for 225 chemicals (USGS National Water Quality Laboratory schedule 5437, S
Nutrient Addition Experiment in the Sacramento River Deep Water Ship Channel
Data were collected in the Sacramento River Deep Water Ship Channel (West Sacramento, CA) in support of a whole-ecosystem experiment investigating whether phytoplankton production and biomass would respond to nitrate additions, which could potentially be exported to food-limited regions in the Sacramento-San Joaquin Delta. The experiment was conducted from July 2 to September 18, 2019. Publicati
Soil physical, chemical, and biological data from edge-of-field agricultural water quality monitoring sites in Great Lakes States
Soil data were collected from catchments of USGS edge-of-field (EOF) monitoring sites in Great Lakes Restoration Initiative (GLRI) priority watersheds. As part of this release, soil data from 2016 through 2019 are provided from 14 sites spanning 5 Great Lake States (Wisconsin, Michigan, Ohio, Indiana, and New York). The data collected are from private farms representing a variety of agronomic syst
Nutrient and sediment concentrations, loads, yields, and rainfall characteristics at USGS surface and subsurface-tile edge-of-field agricultural monitoring sites in Great Lakes States (ver. 2.0, September 2022)
This data release focuses on nutrient and sediment concentrations, loads, and yields at USGS surface and subsurface-tile edge-of-field (EOF) agricultural monitoring sites in Great Lakes States. Water quality and rainfall metrics are summarized by individual flow events to evaluate the contribution of EOF losses to headwater stream networks in agricultural landscapes. USGS EOF sites are components
Below are publications associated with this staff profile.
Filter Total Items: 15
Pesticide prioritization by potential biological effects in tributaries of the Laurentian Great Lakes
Watersheds of the Great Lakes Basin (USA/Canada) are highly modified and impacted by human activities including pesticide use. Despite labeling restrictions intended to minimize risks to nontarget organisms, concerns remain that environmental exposures to pesticides may be occurring at levels negatively impacting nontarget organisms. We used a combination of organismal-level toxicity estimates (in
Prioritizing pesticides of potential concern and identifying potential mixture effects in Great Lakes tributaries using passive samplers
To help meet the objectives of the Great Lakes Restoration Initiative with regard to increasing knowledge about toxic substances, 223 pesticides and pesticide transformation products were monitored in 15 Great Lakes tributaries using polar organic chemical integrative samplers. A screening-level assessment of their potential for biological effects was conducted by computing toxicity quotients (TQs
Whole-ecosystem experiment illustrates short timescale hydrodynamic, light, and nutrient control of primary production in a terminal slough
Estuaries are among the most productive of aquatic ecosystems. Yet the collective understanding of patterns and drivers of primary production in estuaries is incomplete, in part due to complex hydrodynamics and multiple controlling factors that vary at a range of temporal and spatial scales. A whole-ecosystem experiment was conducted in a deep, pelagically dominated terminal channel of the Sacrame
Risk-based prioritization of organic chemicals and locations of ecological concern in sediment from Great Lakes tributaries
With improved analytical techniques, environmental monitoring studies are increasingly able to report the occurrence of tens or hundreds of chemicals per site, making it difficult to identify the most relevant chemicals from a biological standpoint. For this study, organic chemical occurrence was examined, individually and as mixtures, in the context of potential biological effects. Sediment was c
Dispersion and stratification dynamics in the upper Sacramento River deep water ship channel
Hydrodynamics control the movement of water and material within and among habitats, where time-scales of mixing can exert bottom-up regulatory effects on aquatic ecosystems through their influence on primary production. The San Francisco Estuary (estuary) is a low-productivity ecosystem, which is in part responsible for constraining higher trophic levels, including fishes. Many research and habita
Assessment of multiple ecosystem metabolism methods in an estuary
Ecosystem metabolism is a key ecological attribute and easy to describe, but quantifying metabolism in estuaries is challenging. Properly scaling measurements through time and space requires consideration of hydrodynamics and mixing water from heterogeneous sources, making any estimation uncertain. Here, we compared three methods for modeling ecosystem metabolism in a portion of the Sacramento-San
Limited nitrate retention capacity in the Upper Mississippi River
The Mississippi River and other large rivers have the potential to regulate nitrogen export from terrestrial landscapes, and thus mitigate eutrophication in downstream aquatic ecosystems. In large rivers, human-constructed impoundments and connected backwaters may facilitate nitrogen removal; however, the capacity of these features is poorly quantified and incompletely incorporated into model fram
Spatial early warning signals in a lake manipulation
Rapid changes in state have been documented for many of Earth's ecosystems. Despite a growing toolbox of methods for detecting declining resilience or early warning indicators (EWIs) of ecosystem transitions, these methods have rarely been evaluated in whole-ecosystem trials using reference ecosystems. In this study, we experimentally tested EWIs of cyanobacteria blooms based on changes in the spa
Spatial heterogeneity of within-stream methane concentrations
Streams, rivers, and other freshwater features may be significant sources of CH4 to the atmosphere. However, high spatial and temporal variabilities hinder our ability to understand the underlying processes of CH4 production and delivery to streams and also challenge the use of scaling approaches across large areas. We studied a stream having high geomorphic variability to assess the underlying sc
Spatial variability of CO2 concentrations and biogeochemistry in the Lower Columbia River
Carbon dioxide (CO2) emissions from rivers and other inland waters are thought to be a major component of regional and global carbon cycling. In large managed rivers such as the Columbia River, contemporary ecosystem changes such as damming, nutrient enrichment, and increased water residence times may lead to reduced CO2 concentrations (and emissions) due to increased primary production, as has be
The ecology of methane in streams and rivers: Patterns, controls, and global significance
Streams and rivers can substantially modify organic carbon (OC) inputs from terrestrial landscapes, and much of this processing is the result of microbial respiration. While carbon dioxide (CO2) is the major end-product of ecosystem respiration, methane (CH4) is also present in many fluvial environments even though methanogenesis typically requires anoxic conditions that may be scarce in these sys
Regional-scale controls on dissolved nitrous oxide in the Upper Mississippi River
The U.S. Corn Belt is one of the most intensive agricultural regions of the world and is drained by the Upper Mississippi River (UMR), which forms one of the largest drainage basins in the U.S. While the effects of agricultural nitrate (NO3-) on water quality in the UMR have been well documented, its impact on the production of nitrous oxide (N2O) has not been reported. Using a novel equilibration
Non-USGS Publications**
Coyne, K. (2022), What You Think About How Soil and Water Health Connect May Be Wrong. CSA News, 67: 4-10. https://doi.org/10.1002/csan.20907
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Below are software associated with this staff profile.
ToxMixtures: A package to explore toxicity due to chemical mixtures
The ToxMixtures R-package includes a set of functions to analyze, visualize, and organize measured chemical concentration data as it relates to chemical mixtures. ToxMixtures combines outputs from the R-package toxEval with
open access sources on molecular biology to provide information on potential biological effects of chemicals detected in environmental matrices. To use ToxMixtures, the user wi
Science and Products
- Data
Below are data associated with this staff profile.
Pesticides and pesticide transformation product data from passive samplers deployed in 15 Great Lakes tributaries, 2016
This dataset includes pesticides and pesticide transformation products in 15 tributaries of the Great Lakes. Pesticides were monitored using polar organic chemical integrative samplers (POCIS) to estimate concentrations in water following standard protocols (Alvarez, 2010) in June and July 2016. POCIS extracts were analyzed for 225 chemicals (USGS National Water Quality Laboratory schedule 5437, SNutrient Addition Experiment in the Sacramento River Deep Water Ship Channel
Data were collected in the Sacramento River Deep Water Ship Channel (West Sacramento, CA) in support of a whole-ecosystem experiment investigating whether phytoplankton production and biomass would respond to nitrate additions, which could potentially be exported to food-limited regions in the Sacramento-San Joaquin Delta. The experiment was conducted from July 2 to September 18, 2019. PublicatiSoil physical, chemical, and biological data from edge-of-field agricultural water quality monitoring sites in Great Lakes States
Soil data were collected from catchments of USGS edge-of-field (EOF) monitoring sites in Great Lakes Restoration Initiative (GLRI) priority watersheds. As part of this release, soil data from 2016 through 2019 are provided from 14 sites spanning 5 Great Lake States (Wisconsin, Michigan, Ohio, Indiana, and New York). The data collected are from private farms representing a variety of agronomic systNutrient and sediment concentrations, loads, yields, and rainfall characteristics at USGS surface and subsurface-tile edge-of-field agricultural monitoring sites in Great Lakes States (ver. 2.0, September 2022)
This data release focuses on nutrient and sediment concentrations, loads, and yields at USGS surface and subsurface-tile edge-of-field (EOF) agricultural monitoring sites in Great Lakes States. Water quality and rainfall metrics are summarized by individual flow events to evaluate the contribution of EOF losses to headwater stream networks in agricultural landscapes. USGS EOF sites are components - Multimedia
- Publications
Below are publications associated with this staff profile.
Filter Total Items: 15Pesticide prioritization by potential biological effects in tributaries of the Laurentian Great Lakes
Watersheds of the Great Lakes Basin (USA/Canada) are highly modified and impacted by human activities including pesticide use. Despite labeling restrictions intended to minimize risks to nontarget organisms, concerns remain that environmental exposures to pesticides may be occurring at levels negatively impacting nontarget organisms. We used a combination of organismal-level toxicity estimates (inPrioritizing pesticides of potential concern and identifying potential mixture effects in Great Lakes tributaries using passive samplers
To help meet the objectives of the Great Lakes Restoration Initiative with regard to increasing knowledge about toxic substances, 223 pesticides and pesticide transformation products were monitored in 15 Great Lakes tributaries using polar organic chemical integrative samplers. A screening-level assessment of their potential for biological effects was conducted by computing toxicity quotients (TQsWhole-ecosystem experiment illustrates short timescale hydrodynamic, light, and nutrient control of primary production in a terminal slough
Estuaries are among the most productive of aquatic ecosystems. Yet the collective understanding of patterns and drivers of primary production in estuaries is incomplete, in part due to complex hydrodynamics and multiple controlling factors that vary at a range of temporal and spatial scales. A whole-ecosystem experiment was conducted in a deep, pelagically dominated terminal channel of the SacrameRisk-based prioritization of organic chemicals and locations of ecological concern in sediment from Great Lakes tributaries
With improved analytical techniques, environmental monitoring studies are increasingly able to report the occurrence of tens or hundreds of chemicals per site, making it difficult to identify the most relevant chemicals from a biological standpoint. For this study, organic chemical occurrence was examined, individually and as mixtures, in the context of potential biological effects. Sediment was cDispersion and stratification dynamics in the upper Sacramento River deep water ship channel
Hydrodynamics control the movement of water and material within and among habitats, where time-scales of mixing can exert bottom-up regulatory effects on aquatic ecosystems through their influence on primary production. The San Francisco Estuary (estuary) is a low-productivity ecosystem, which is in part responsible for constraining higher trophic levels, including fishes. Many research and habitaAssessment of multiple ecosystem metabolism methods in an estuary
Ecosystem metabolism is a key ecological attribute and easy to describe, but quantifying metabolism in estuaries is challenging. Properly scaling measurements through time and space requires consideration of hydrodynamics and mixing water from heterogeneous sources, making any estimation uncertain. Here, we compared three methods for modeling ecosystem metabolism in a portion of the Sacramento-SanLimited nitrate retention capacity in the Upper Mississippi River
The Mississippi River and other large rivers have the potential to regulate nitrogen export from terrestrial landscapes, and thus mitigate eutrophication in downstream aquatic ecosystems. In large rivers, human-constructed impoundments and connected backwaters may facilitate nitrogen removal; however, the capacity of these features is poorly quantified and incompletely incorporated into model framSpatial early warning signals in a lake manipulation
Rapid changes in state have been documented for many of Earth's ecosystems. Despite a growing toolbox of methods for detecting declining resilience or early warning indicators (EWIs) of ecosystem transitions, these methods have rarely been evaluated in whole-ecosystem trials using reference ecosystems. In this study, we experimentally tested EWIs of cyanobacteria blooms based on changes in the spaSpatial heterogeneity of within-stream methane concentrations
Streams, rivers, and other freshwater features may be significant sources of CH4 to the atmosphere. However, high spatial and temporal variabilities hinder our ability to understand the underlying processes of CH4 production and delivery to streams and also challenge the use of scaling approaches across large areas. We studied a stream having high geomorphic variability to assess the underlying scSpatial variability of CO2 concentrations and biogeochemistry in the Lower Columbia River
Carbon dioxide (CO2) emissions from rivers and other inland waters are thought to be a major component of regional and global carbon cycling. In large managed rivers such as the Columbia River, contemporary ecosystem changes such as damming, nutrient enrichment, and increased water residence times may lead to reduced CO2 concentrations (and emissions) due to increased primary production, as has beThe ecology of methane in streams and rivers: Patterns, controls, and global significance
Streams and rivers can substantially modify organic carbon (OC) inputs from terrestrial landscapes, and much of this processing is the result of microbial respiration. While carbon dioxide (CO2) is the major end-product of ecosystem respiration, methane (CH4) is also present in many fluvial environments even though methanogenesis typically requires anoxic conditions that may be scarce in these sysRegional-scale controls on dissolved nitrous oxide in the Upper Mississippi River
The U.S. Corn Belt is one of the most intensive agricultural regions of the world and is drained by the Upper Mississippi River (UMR), which forms one of the largest drainage basins in the U.S. While the effects of agricultural nitrate (NO3-) on water quality in the UMR have been well documented, its impact on the production of nitrous oxide (N2O) has not been reported. Using a novel equilibrationNon-USGS Publications**
Coyne, K. (2022), What You Think About How Soil and Water Health Connect May Be Wrong. CSA News, 67: 4-10. https://doi.org/10.1002/csan.20907**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
- Software
Below are software associated with this staff profile.
ToxMixtures: A package to explore toxicity due to chemical mixtures
The ToxMixtures R-package includes a set of functions to analyze, visualize, and organize measured chemical concentration data as it relates to chemical mixtures. ToxMixtures combines outputs from the R-package toxEval with open access sources on molecular biology to provide information on potential biological effects of chemicals detected in environmental matrices. To use ToxMixtures, the user wi
*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government