About

We seek to understand how freshwater ecosystems support aquatic invertebrates that sustain foodwebs threatened by environmental change.

Research topics

• Ecology
• Biology
• Environmental science
• Geology
• Geography

Selected publications

• Author response for "Anemic streams: Iron and essential trace metals frequently limit primary producer biomass"

  2026-02-05

  peer-review
  PublisherDOI

• Author response for "Anemic streams: Iron and essential trace metals frequently limit primary producer biomass"

  2026-02-16

  peer-review
  PublisherDOI

• Anaemic Streams: Iron and Essential Trace Metals Frequently Limit Primary Producer Biomass

  Ecology Letters · 2026-03-01

  articleOpen access

  Metals are essential for microbial metabolism, yet their role as limiting nutrients in freshwater streams remains poorly understood. We quantified the prevalence of metal and nutrient (co-)limitation of primary producers in 41 streams. Metal limitation was widespread with Fe limitation eliciting the strongest and most consistent biomass responses (50% of streams). Zn limitation was also common (33% of streams), marking the first evidence of Zn-limited stream biofilms at this spatial scale. Metals were often co-limiting with N and P, highlighting interactions between macro- and micronutrients. Diatoms were more responsive to Zn and cyanobacteria reached higher biomass with N and P enrichment, emphasizing divergent nutrient responses among taxa. Predictive modelling indicated that Fe and Zn limitation could be forecasted from environmental variables related to macronutrient supply. These findings challenge the long-standing assumption that stream primary producers are rarely metal-limited and suggest that trace metals may play an underappreciated role in regulating stream productivity, community composition and nutrient cycling.

  PublisherDOI

• lmt-ops/OrganicMatterInHeadwaterStreamsOfCentralApplachianCoalfield: Organic matter composition but not the amount changed across a mining-induced salinization gradient in central Appalachian headwater streams

  Zenodo (CERN European Organization for Nuclear Research) · 2026-04-07

  otherOpen accessSenior author

  Code and data for the manuscript: "Organic matter composition but not the amount changed across a mining-induced salinization gradient in central Appalachian headwater streams".

  PublisherDOI

• Tradeoffs between elemental homeostasis and growth govern freshwater phytoplankton responses to salinization

  Limnology and Oceanography · 2025-06-02 · 1 citations

  articleOpen access

  Abstract Anthropogenic salinization resulting from road salt application can degrade aquatic environments by altering the structure and function of phytoplankton communities, ultimately reducing flows of resources through aquatic food webs. However, physiological mechanisms underlying taxon‐specific responses to salinization are often poorly linked to higher‐order ecosystem dynamics, limiting our ability to predict community responses to salinization. To this end, we tested hypotheses derived from Subsidy‐Stress and Ecological Stoichiometry theory by growing two cosmopolitan genera, Dolichospermum (prokaryotic, cyanobacteria) and Scenedesmus (eukaryotic, green algae), across NaCl gradients and contrasting differences in their growth rates, degree of Na homeostasis, and cellular C : N : P ratios. We found mixed support for the subsidy‐stress hypothesis, with only stress responses observed for both species. Instead, growth declines appeared to be linked to stoichiometric tradeoffs between growth and homeostatic regulation, with stronger homeostatic Na regulation coinciding with a greater reduction in Scenedesmus growth rates and higher variation in their stoichiometric C : N : P ratios across NaCl gradients. Nonhomeostatic Na regulation allowed Dolichospermum to sustain higher growth rates, which appeared to constrain variation in their stoichiometric C : N : P ratios along with their stronger physiological regulation of intracellular P storage molecule production. Differences in phytoplankton growth responses were consistent with stoichiometric theory and field observations documenting shifts from green algae to cyanobacteria in response to freshwater salinization. Our results suggest that these shifts could take place below existing North American chronic threshold limits, resulting in decreased production at higher trophic levels by reducing phytoplankton biomass production rates and inducing nutritional stress in consumers.

  PublisherOA PDFDOI

• CAN INSECT CARBON STABLE ISOTOPES IN TEMPERATE, C3 DOMINATED ENVIRONMENTS IDENTIFY LONG-TERM VEGETATION CHANGES?

  Abstracts with programs - Geological Society of America · 2025-01-01

  article
  PublisherDOI

• Macroinvertebrate inventory of high elevation springs in Shenandoah National Park, 2022–2024

  National Park Service · 2025-01-01

  reportSenior author

  Virginia Tech partnered with the National Park Service Inventory and Monitoring program to sample macroinvertebrates and environmental measures related to water quality, habitat availability, and human use at 63 springs within Shenandoah National Park, of which 59 were assessed and analyzed. Thirty five of the 59 springs had been intentionally modified for human use via spring box or pipe installation and the remaining 25 had not been modified. The goals of this inventory were to assess the distributions of macroinvertebrates across springs in the park with an emphasis on identifying unique spring specialist taxa that might be considered rare. Additionally, we sought to determine whether macroinvertebrate diversity and the presence of rare taxa have been impacted by modifications made to springs and/or by visitor use (springs that are frequently visited/used by park goers). We identified 205 unique taxa across the 59 springs. Of those taxa, we identified 17 rare taxa using NatureServe’s Conservation Status Rank, where species with a status rank of at least vulnerable were labeled rare. Rare taxa were present in 32 springs, 19 of which were modified (having a spring box or pipe installed) and 13 were unmodified (no installations). There was no statistically significant difference in total taxa richness or abundance between the spring types. General linear models indicated decreased pH, flow (velocity), small woody debris, and increased proximity of springs to a spring signpost as factors associated with increased taxa richness in the macroinvertebrate community, while richness for rare taxa were most associated with increasing temperature, small woody debris, and increased distance (decreased proximity) of springs to a spring signpost. Furthermore, linear models showed that decreasing pH, flow, temperature, small woody debris, and increased proximity of springs to a spring signpost or Appalachian Trail shelters (referred to as AT huts) were associated with increased abundance of macroinvertebrate taxa, while decreases in temperature, increased cobble substrate, and increased proximity to spring signposts were associated with greater abundances of rare taxa. The diversity of spring types, locations and habitats appear to support a diversity of species that are not being negatively affected by visitor usage or spring box infrastructure. The springs provide a regional spec

  PublisherDOI

• Full life cycle assessment of insect biomass allows estimation of bioflows across water, air, and land

  Ecosphere · 2024-11-01

  articleOpen accessSenior author

  Abstract As global environmental change continues, animals face uncertain habitat availability and quality that influences life cycle phenology and population dynamics. For decades, the population abundance and emergence patterns of burrowing mayflies have been used as a sentinel for water quality changes in large freshwater systems around the world. Despite reduced point source pollutants, evidence is mounting that the interactions among habitat loss, contaminants, and changing climate could be causing declines in mayfly production and shifts in emergence timing. We combined radar observations with traditional field measures to identify changes in mayfly populations from nymph to adult. We studied Hexagenia sp. secondary production in a large reservoir, Lake Seminole, which has contrasting water sources and land use on each arm that could contribute to differences in emergence patterns. We predicted that mayfly secondary production would be higher, and emergence would be earlier in the Chattahoochee arm versus the Flint arm because of differences in available nutrients and temperature. Benthic declines in abundance and biomass followed radar observations of emergence. Mean annual water temperature was similar, with the Flint arm having less seasonal variation. Mayfly growth was similar across the lake, but production was higher in the upper Flint arm, perhaps because of temperature stability, higher nutrient concentrations, and more lotic conditions. The natural abundance of nitrogen‐stable isotopes in mayflies showed distinct patterns between the arms and from nymph to adult. Linking benthic sampling with radar observations verified our capability to track mayfly biomass across the landscape and begin to calibrate previous measures of production with radar‐derived abundance. Coupling radar observations with stable isotope and tissue nutrient measurements allowed us to further quantify the subsidies moving from aquatic to terrestrial ecosystems, setting the framework to examine both historic and future population changes and mayfly contributions to cross‐ecosystem subsidies.

  PublisherOA PDFDOI

• Connecting conservation practices to local stream health in the Chesapeake Bay watershed

  Fact sheet · 2024-01-01 · 2 citations

  articleOpen access

  First posted July 19, 2024 For additional information, contact: Chesapeake Bay ActivitiesU.S. Geological Survey5522 Research Park DriveBaltimore, MD 21228Contact Pubs Warehouse The Chesapeake Bay Partnership is implementing conservation practices (CPs) throughout the Chesapeake Bay watershed to reduce nutrient and sediment delivery to the Bay. This study intends to provide an integrated and detailed understanding of how local streams respond to these CP-driven management efforts.Key issue: To what extent do CPs positively affect the health of local streams in the nontidal watershed (cobenefits)?Critical unknown: How do CPs change water quality and the stressors that affect stream aquatic life? Which CPs improve stream health more effectively?Critical knowledge to be delivered to stakeholders includes—the effects of CPs on local water-quality conditions,the degree to which these same CPs also provide local stream-ecosystem benefits, anda deeper understanding of local stream-ecosystems, including stressors and CPs, to guide the selection of management efforts that enhance both water quality and overall stream-ecosystem health.

  PublisherOA PDFDOI

• Human activities shape global patterns of decomposition rates in rivers

  Science · 2024-05-30 · 31 citations

  articleOpen access

  Rivers and streams contribute to global carbon cycling by decomposing immense quantities of terrestrial plant matter. However, decomposition rates are highly variable and large-scale patterns and drivers of this process remain poorly understood. Using a cellulose-based assay to reflect the primary constituent of plant detritus, we generated a predictive model (81% variance explained) for cellulose decomposition rates across 514 globally distributed streams. A large number of variables were important for predicting decomposition, highlighting the complexity of this process at the global scale. Predicted cellulose decomposition rates, when combined with genus-level litter quality attributes, explain published leaf litter decomposition rates with high accuracy (70% variance explained). Our global map provides estimates of rates across vast understudied areas of Earth and reveals rapid decomposition across continental-scale areas dominated by human activities.

  PublisherOA PDFDOI

Frequent coauthors

• Michelle A. Evans‐White

  University of Arkansas at Fayetteville

  36 shared

• Emma J. Rosi

  Cary Institute of Ecosystem Studies

  24 shared

• Timothy J. Hoellein

  Loyola University Chicago

  23 shared

• Jennifer L. Tank

  University of Notre Dame

  21 shared

• Gary A. Lamberti

  University of Notre Dame

  15 shared

• Bradley J. Austin

  University of Arkansas System

  13 shared

• Richard H. Walker

  University of Tennessee at Chattanooga

  12 shared

• Jean‐Philippe Nicot

  Bureau of Economic Analysis

  12 shared

Labs

• Virginia Tech Aquatic Entomology LabPI