News & Updates
2024-05-15 - Hotchkiss co-authors article on ecosystem responses to freshwater salinization
Citation: DeVilbiss, S.E., Badgley, B.D., Hotchkiss, E.R., & Steele, M.K. 2024. Subsidy-stress responses of ecosystem functions along experimental freshwater salinity gradients. Biogeochemistry 167, 743–757. https://doi.org/10.1007/s10533-024-01131-5
Abstract: "Human activity is increasing salt concentrations in freshwaters worldwide, but effects of freshwater salinity gradients on biogeochemical cycling are less understood than in saline, brackish, or marine environments. Using controlled microcosm experiments, we characterized (1) short-term (one to five days) biogeochemical responses and (2) water column metabolism along a freshwater salinity gradient of multiple salt types. After one day, microcosms were oxic (4.48–7.40 mg O2 L−1) but became hypoxic (1.20–3.31 mg L−1) by day five. After one day in oxic conditions, microbial respiration in magnesium-, sodium-, and sea salt-based salinity treatments showed a subsidy-stress response, with respiration increasing by over 100% as salinity increased from 30 to 350–800 µS cm−1. Conversely, respiration consistently increased along a calcium-based salinity gradient, peaking at 1500 µS cm−1. By day five, an inverse subsidy-stress response was observed with elevated respiration at upper or lower ends of the gradient except for the magnesium treatment, which had the lowest respiration at the highest salinity. Calcium- and magnesium-based salinity treatments also caused considerable changes in phosphorus concentrations and C:P and N:P. In a separate experiment, microbial respiration and water column primary production also displayed subsidy-stress responses, but imbalances in effect sizes caused consistently declining net community production with increasing salinity. Collectively, our results establish that short-term exposure to different salt ion concentrations can enhance freshwater biogeochemical cycling at relatively low concentrations and alter resource stoichiometry. Furthermore, the nature of effects of freshwater salinization may also change with oxygen availability."
Figure 1 in DeVilbiss et al. (2024). 'Microbial respiration rates along experimental freshwater salinity gradients of CaCl2 (top row), MgCl2 (second row), NaCl (third row), and artificial sea salt (bottom row) under oxic (left column) and hypoxic (right column) conditions. More negative values indicate higher oxygen consumption.'
Figure 2 in DeVilbiss et al. (2024). 'Effects of different chloride salts on microbial respiration at four distinct salinities. The left column shows respiration after a 1-day incubation and the right column after a 5-day incubation that started in oxic conditions but became hypoxic during the 5 days. More negative values indicate greater oxygen consumption. Significant differences in respiration among salt types are shown with letters (p < 0.05).'
Figure 3 in DeVilbiss et al. (2024). 'Net fluxes of dissolved organic carbon (DOC, top row), NH4+ (second row), NO3− (third row), and PO43− (bottom row) along experimental salinity gradients of CaCl2 (first column), MgCl2 (second column), NaCl (third column), and artificial sea salt (last column) in oxic (A) and hypoxic (B) conditions. Positive values indicate net release, negative values indicate net uptake. Dashed lines are at 0, indicating the transition from release to uptake.'
Figure 5 in DeVilbiss et al. (2024). 'Response of community respiration (CR), gross primary production (GPP), and net community production (NCP) along experimental salinity gradients of two salt profiles including a combination of calcium, magnesium, and potassium chloride salts (Ca:Mg:K) and sodium chloride (NaCl). Panel A shows measured oxygen flux values and panel B shows percent change from unaltered reference water. Positive values indicate oxygen production, negative values indicate oxygen consumption.'
2024-06-13 - Pictures from SFS in Philadelphia
Thanks to all attendees for contributing to a great Society for Freshwater Science annual meeting! Pictured above:
Left column, top-bottom: (1) Tiffany Meadows (VT undergraduate) and Ally Kaelin (VT 2024 grad) presenting their poster on "Assessing terrestrial and aquatic resource dynamics in streams across biomes"; (2) Evie Dana and Isabella Korobow-Velez (VT undergraduates) presenting their poster on "Species abundance and food web structure across biomes"; & (3) the five current undergraduates and spring 2024 VT grads in our lab who attended SFS at the Swann Memorial Fountain in Logan Square (Emily Mulcahy, Ally Kaelin, Tiffany Meadows, Evie Dana, & Isabella Korobow-Velez).
Middle, top-bottom: (1) Group photo of current members, affiliates, and recent graduates of the lab: Evie Dana, Frances Iannucci, Ally Kaelin (BSc, VT BIOL 2024), Isabella Korobow-Velez, Tiffany Meadows, Erin Hotchkiss, Katherine Pérez Rivera, Stephen Plont (PhD, VT BIOL 2023), Caleigh Meehan, & Emily Mulcahy (BSc, VT BIOL 2024). (2) Katherine Pérez Rivera (PhD student) giving her presentation on "Longitudinal patterns in carbon cycling along a stream continuum draining a heterogeneous landscape".
Right column, top-bottom: (1) Caleigh Meehan (Master's student) presenting her poster on "Consequences of freshwater salinization on stream carbon cycling"; (2) Emily Mulcahy (VT 2024 grad) presenting her poster on "Assessing the role of phytoplankton on the biogeochemistry in geographically isolated wetlands"; (3) lab collaborator Kristin Olson (PhD Candidate, University of Alaska Fairbanks) presenting her poster on "In the boreal forest net carbon exchange puzzle, how big of a piece are stream CO2 emissions?"; and (4) lab affiliate / Stream Team Analytical Laboratory Manager and Data Scientist, Frances Iannucci, presenting her poster on "Contrasting roles of discharge on shaping headwater stream CO2 regimes".
2024-05-31 - Learn about our ongoing research at the Society for Freshwater Science Conference in Philadelphia, PA
We're looking forward to sharing our science, reconnecting with collaborators/friends, & meeting new freshwater scientists next week! https://sfsannualmeeting.org/
2024-05-15 - Congratulations, Spring 2024 graduates!
We are celebrating the graduation of three undergraduate researchers in the lab this year: Emily Mulcahy, Allyson Kaelin, and Caroline Brickner. We're sorry to see you leave, but excited for all that you'll accomplish.
We also celebrate past undergraduate researchers in the lab who graduated this year: Carmen Curry, Cleo Orlando, & Gavriel Cambridge.
Congratulations, everyone!
Allyson Kaelin
Biological Sciences
After graduation: Ally will be working as a Scientist at the Naval Surface Warfare Center, Dahlgren Division
Emily Mulcahy
Biological Sciences, Wetland Science, & Green Engineering
After graduation: Emily will be starting a Master's program in Biology at the University of Louisiana at Lafayette
Caroline Brickner
Biological Sciences
After graduation: Caroline is taking time to explore different careers in Biology
2024-04-26 - Spring 2024 Undergraduate Research Conference
Several undergraduate researchers collaborating with members of the Hotchkiss Lab shared their science at this year's Dennis Dean Undergraduate Research and Creative Scholarship Conference at Virginia Tech. Congratulations on fantastic posters presentations - we've enjoyed collaborating with all of you!
Emma Lucier & James Logan
Lucier*, Logan*, Hotchkiss, Campo, Flota, Huo, Penland, & Pérez Rivera. 2024. Differences in Water Quality Above and Below a Retention Pond: Implications for Ecosystem Health and Predicted Effects of Dredging. Dennis Dean Undergraduate Research and Creative Scholarship, Virginia Tech, Blacksburg, VA, USA.
Collaboration Team: Spring 2024 Ecology Research in Local Waterways
(BIOL 2984)
*Awarded 3rd place out of all posters evaluated by the College of Natural Resources and the Environment* (congrats, team!)
Emily Mulcahy
Mulcahy*, López Lloreda, Wardinski, Corline, & Hotchkiss. 2024. Assessing the Role of Phytoplankton on the Biogeochemistry in Geographically Isolated Wetlands. Dennis Dean Undergraduate Research and Creative Scholarship, Virginia Tech, Blacksburg, VA, USA.
Collaboration Team: Delmarva Disco
(NSF DEB 1856560)
Isabella Korobow & Evie Dana
Dana*, Korobow-Velez*, Rasmussen, Rowe, Brickner, Kaelin, Masters, Meadows, & Hotchkiss. 2024. Assessing Macroinvertebrate and Primary Producer Populations and Their Habitats Across Biomes. Dennis Dean Undergraduate Research and Creative Scholarship, Virginia Tech, Blacksburg, VA, USA.
Collaboration Team: Macrosystems Ecology Research Team
(NSF DEB 1926426)
Jared Rasmussen & Peyton Rowe
Rasmussen*, Rowe*, Brickner, Dana, Kaelin, Korobow-Velez, Masters, Meadows, & Hotchkiss. 2024. Observing changes in macroinvertebrate density and evenness across biomes. Dennis Dean Undergraduate Research and Creative Scholarship, Virginia Tech, Blacksburg, VA, USA.
Collaboration Team: Macrosystems Ecology Research Team
(NSF DEB 1926426)
2024-02-22 - Photos from the field: Ecology Research in Local Waterways Class
Erin Hotchkiss and Katherine Pérez Rivera are conducting research with a team of undergraduates this semester through a new course developed by Hotchkiss: Ecology Research in Local Waterways. The course is open to all students with sophomore standing or higher; no prior experience in research or freshwater science is required for enrollment. We aim to provide students with real-world freshwater science knowledge, research experience, and team science best practices through a semester-long collaboration; the research goals will change each semester to reflect ongoing freshwater research needs and opportunities on Virginia Tech's Blacksburg campus and/or the surrounding area. This spring, our research collaboration is testing the downstream water quality effects of the Duck Pond, a large retention pond on Virginia Tech's campus that is part of the Stroubles Creek stream network. In addition to testing the current capacity of the Duck Pond to reduce downstream sediment, nutrient, and salt pollution, we will also monitor upstream and downstream water quality during a contracted dredging project that will remove built-up sediments from the Duck Pond and increase its future retention capacity. Below are a few photos of our collaboration team collecting samples to measure stream flow and water quality above and below the Duck Pond; stay tuned for more updates on what we learn this semester! The next section of this class will be offered in Fall 2024.
2024-01-12 - López Lloreda presents at BIOGEOMON 2024
Carla López Lloreda recently gave a presentation at the 11th BIOGEOMON International Symposium on Ecosystem Behavior in San Juan, Puerto Rico. Her talk was titled "Disturbances drive stream greenhouse gas changes and increased heterogeneity at the reach-scale" and was co-authored by Allison Herreid, Tatiana Barreto Vélez, Jesús Gómez, Pablo Gutiérrez-Fonseca, and William H. McDowell.
