News & Updates

2022 Archive

2022-12-20 - Happy Holidays from the Lab!

Left to right: Erin Hotchkiss, Carla López Lloreda, Stephen Plont, Katherine Pérez-Rivera, & Kristen Bretz showing off their festive cats and dinosaurs!

2022-12-16 - Hotchkiss gave invited talk at AGU

Erin Hotchkiss gave an invited talk at the American Geophysical Union (AGU) fall meeting in Chicago; enjoyed interacting with colleagues and participating in events as an Associate Editor of the Journal of Geophysical Research - Biogeosciences; and co-authored one poster and one virtual talk.

Presentation authors and titles:

  • Hotchkiss, E.R. & K.A. Bretz. 2022. Warming waters, whole-ecosystem metabolism, and carbon fate in streams. American Geophysical Union. Chicago, IL. Invited talk in special session.

  • Abir, A.H., W.M. Wollheim, E.R. Hotchkiss, D.E. Butman, J. Jones, L. Munro, K. Cawley, & K.J. Goodman. 2022. Partitioning the fate of soil carbon dioxide between losses to atmosphere and subsurface hydrologic flowpaths. American Geophysical Union. Chicago, IL. Poster.

  • Entrekin, S., A. James, D.L. McLaughlin, S. Schoenholtz, C.E. Zipper, E.R. Hotchkiss, G. Pond, & T. Timpano. 2022. Aquatic food web changes in response to mining-induced salinization in Appalachian headwaters. American Geophysical Union. Chicago, IL. Virtual presentation.

2022-12-01 - López Lloreda co-authors article on greenhouse gas dynamics in Puerto Rican streams

Carla López Lloreda is co-author of a new article in Biogeochemistry characterizing "Greenhouse gas dynamics in tropical montane streams of Puerto Rico and the role of watershed lithology". From the abstract: "We use a five-year record of weekly water chemistry and dissolved gas data from eight tropical watersheds of varying lithology and redox conditions in the Luquillo Mountains of Puerto Rico to examine controls on GHG [greenhouse gas] variability and estimate gas flux. Streams were frequently supersaturated in all three gases indicating that streams in this tropical landscape are sources of GHGs to the atmosphere. Concentrations of CO2 and N2O were associated with lateral inputs from the surrounding landscape, whereas CH4 concentrations correlated with in-stream oxygen availability and lithology. Our results underscore the importance of including tropical sites in global syntheses and budgets and the role of both in-stream biological and physical processes as well as landscape attributes that contribute to the export of gases to the fluvial network and atmosphere."

Citation: Herreid, A.M., C. López Lloreda, A.S. Wymore, J.D. Potter, & W.H. McDowell. 2022. Greenhouse gas dynamics in tropical montane streams of Puerto Rico and the role of watershed lithology. Biogeochemistry

Congratulations, Carla and co-authors!

2022-11-21 - Hotchkiss co-authors two articles on ecosystem respiration in streams and rivers

Hotchkiss co-authored two recent articles advancing our understanding of whole-ecosystem respiration in streams and rivers:

  1. Tromboni, F., E.R. Hotchkiss, A.E. Schechner, W.K. Dodds, S.R. Poulson, & S. Chandra. 2022. High rates of daytime river metabolism are an underestimated component of carbon cycling. Communications Earth & Environment 3: 270.

    We used diel changes in dissolved oxygen concentrations and stable isotope values, estimates of oxygen fractionation during respiration, and Bayesian inverse modeling to test the assumption that ecosystem respiration is constant over 24 hours in streams and rivers across the globe. We found evidence for higher daytime respiration at all sites. From the abstract: "Through accounting for diel variation in ecosystem respiration, our isotopically-derived rates suggest that ecosystem respiration and microbial carbon cycling in rivers is more rapid than predicted by traditional methods."

  1. Bertuzzo, E., E.R. Hotchkiss, A. Argerich, J.S. Kominoski, D. Oviedo-Vargas, P. Savoy, R. Scarlett, D. von Schiller, & J.B. Heffernan. 2022. Respiration regimes in rivers: Partitioning source-specific respiration from metabolism time series. Limnology & Oceanography 67: 2374-2388.

    We leveraged multi-year time series of whole-stream metabolism estimates for five streams and rivers to develop a modeling framework that assigns proportions of daily respiration coming from different organic matter sources: internal algal and plant production, leaf litter, dissolved organic matter pulses during high flows, and baseline respiration sustained by detrital organic matter in sediments. From the abstract: "Overall, the model explained between 53% and 74% of observed ER dynamics. Respiration of autochthonous OM tracked seasonal peaks in GPP in spring or summer. Increases in ER were often associated with high-flow events. Respiration associated with litter inputs was larger in smaller streams. Time lags between leaf inputs and respiration were longer than for other OM sources, likely due to lower biological reactivity. Model estimates of source-specific ER and OM stocks compared well with existing measures of OM stocks, inputs, and respiration or decomposition. Our modeling approach has the potential to expand the scale of comparative analyses of OM dynamics within and among freshwater ecosystems."

Thank you to Flavia Tromboni and Enrico Bertuzzo for leading these papers and thanks to all co-authors for the fun collaborations!

2022-11-01 - Hotchkiss co-authors article on common pool resource theory and freshwater salinization

Hotchkiss is a co-author on a recent article published in Environmental Science & Technology that highlights perspectives from our Growing Convergence Research collaborative project on "Common Pool Resource Theory as a Scalable Framework for Catalyzing Stakeholder-Driven Solutions to the Freshwater Salinization Syndrome" led by Stanley Grant at Virginia Tech (NSF 2021015).

Citation: Grant, S.B., M.A. Rippy, T.A. Birkland, T. Schenk, K. Rowles, S. Misra, P. Aminpour, S. Kaushal, P. Vikesland, E. Berglund, J.D. Gomez-Velez, E.R. Hotchkiss, G. Perez, H.X. Zhang, K. Armstrong, S. Bhide, L. Krauss, C. Maas, K. Mendoza, C. Shipman, Y. Zhang, & Y. Zhong. 2022. Can common pool resource theory catalyze stakeholder-driven solutions to the freshwater salinization syndrome? Environmental Science & Technology 56: 13517-13527. doi:10.1021/acs.est.2c01555.

Graphical abstract from Grant et al. (2022) highlighting the opportunity to integrate Ostrom's social-ecological systems framework for common pool resource theory, stakeholder knowledge, bottom-up management, and researcher knowledge to address the freshwater salinization syndrome.
Figure 2 from Grant et al. (2022): (Left) Ostrom’s Social-Ecological-Systems (SES) framework for common pool resource management, applied here to sodium [Na+] management in the Occoquan Reservoir. Green circles represent first-level subsystems. OWMP, Occoquan Watershed Monitoring Program. (Right) 10 key second-level variables associated with the likelihood that collective management of the resource is feasible (alphanumeric codes from Ostrom 2009). Similar diagrams can be prepared for other ions and ecosystem services.

2022-10-21 - VT College of Science Undergraduate Research Mixer

Carla López Lloreda, Katherine Pérez Rivera, and Kristen Bretz attended the Fall 2022 College of Science Undergraduate Research Mixer to share information about ongoing research and future opportunities with our lab group. We're excited to be increasing our capacity for undergraduate collaborators in spring/summer 2023 through ongoing research related to Katherine's and Carla's dissertation projects. Thanks for sharing our science, Kristen, Katherine, and Carla!

Kristen Bretz, Katherine Pérez Rivera, and Carla López Lloreda talk about research opportunities with students at Virginia Tech's College of Science Undergraduate Research Mixer. Photos courtesy of VT College of Science.

2022-09-19 - Wardinski leads paper on soil organic matter at the terrestrial-aquatic interface of wetlands

Katie Wardinski, a MSc/PhD student collaborating on our NSF-funded "Hydrologic Connectivity and Water Storage as Drivers of Carbon Export and Emissions from Wetland-Dominated Catchments" project and a current PhD student working with Durelle Scott, published her Master's research characterizing "Water soluble organic matter from soils at the terrestrial-aquatic interface in wetland-dominated landscapes" in the Journal of Geophysical Research – Biogeosciences. Congratulations, Katie! Well done.

From the plain language summary of the paper: "Wetlands store carbon in their plant biomass and soils, which helps mitigate the effects of climate change by keeping carbon out of the atmosphere. However, the organic matter (including carbon) that accumulates in wetland soils may be released into water, generating dissolved organic matter (DOM). This DOM has the potential to flow out of wetlands, providing a source of energy to aquatic organisms and altering downstream water quality. We studied the potential for soil-derived DOM generation by extracting water-soluble organic matter (WSOM) from soils along a wet to dry gradient in Delmarva Bay wetlands. Shallow soils had the highest concentrations of WSOM and this organic matter is likely sourced from plant inputs to the soil. WSOM from deeper soils was more similar to the microbes that consume and alter the organic matter as it cycles deeper into the soil. Soils located in the wetland basin had less WSOM because continuous saturation depleted the pool of WSOM. Despite lower amounts of WSOM, wetland soils are thick and continuously saturated, making these soils the largest potential contributor of soil-derived DOM to Delmarva Bay wetlands and downstream ecosystems. This work furthers our understanding of how hydrology drives carbon cycling in wetland-dominated landscapes."

Citation: Wardinski, K.M., E.R. Hotchkiss, C.N. Jones, D.L. McLaughlin, B.D. Strahm, & D.T. Scott. 2022. Water soluble organic matter from soils at the terrestrial-aquatic interface in wetland-dominated landscapes. Journal of Geophysical Research – Biogeosciences 127: e2022JG006994. doi:10.1029/2022JG006994.

2022-09-16 - Hotchkiss co-authors article testing how non-native beavers alter stream metabolism

Beavers are ecosystem engineers whose presence can increase ecosystem resilience and sustain biodiversity in their native region. But how are non-native beaver introductions (and ongoing removal by managers) in southern Argentina changing ecosystem functions? Past work by Erin's co-authors, Dr. Victoria García and Dr. Patricia Rodríguez (Centro Austral de Investigaciones Científcas & Instituto de Ciencias Polares, Ambiente y Recursos Naturales, Universidad Nacional de Tierra del Fuego) characterized the potential impacts of non-native beavers on periphyton metabolism and other limnological variables in Fuegian rivers and streams as well as the Beaver dam effect on phytoplankton and periphyton composition and hydrology in streams from Tierra del Fuego (Argentina)”.

Our collaboration integrated short-term (1-4 day) estimates of ecosystem metabolism with other data from invaded streams to compare ecosystem function in sites with active beaver dams (non-native beaver still present) versus abandoned sites (due to ongoing beaver eradication efforts). Streams with ongoing beaver activity typically had higher Gross Primary Production (GPP) and ecosystem respiration (ER) upstream of beaver dams compared to downstream, and had also higher metabolic rates than sites with abandoned dams due to the removal of non-native beavers. This work was supported by a visiting postdoc fellowship awarded to Victoria for a research exchange hosted by the Department of Biological Sciences at Virginia Tech. Thanks for a fun collaboration, Victoria and Patricia!

Citation: García, V.J., E.R. Hotchkiss, & P. Rodríguez S. 2022. Ecosystem metabolism in sub-Antarctic streams and rivers impacted by non-native beaver. Aquatic Sciences 84:54. doi: 10.1007/s00027-022-00876-1.

2022-08-30 - Hotchkiss is co-PI on new NSF-funded project testing how mining-induced freshwater salinization alters food web energetics and carbon cycling in Appalachian streams

2022-09-30 Update: You can learn more about our newly funded collaboration in a recent news post from the Global Change Center, which funded this project through an earlier seed grant that supported the development of our successful NSF proposal.

2022-08-19 - Pérez Rivera reflects on her Fulbright exchange in the Czech Republic

Katherine Pérez Rivera recently published an article in the FULBRIGHT REALITY CZECH blog reflecting on her experiences during a Fulbright exchange hosted by Dr. Pavel Krám at the Česká Geologická Služba (Czech Geological Survey): "Katherine Pérez Rivera: Beyond science - collaboration, engagement, and identity" Congratulations on all that you accomplished this past year, Katherine!

2022-08-09 - MacroCO2 project meeting in Colorado

Erin met with collaborators from the University of Washington (David Butman, Hannah Conroy), University of Alaska-Fairbanks (Jay Jones, Kristin Olson, Frances Iannucci), University of New Hampshire (Wil Wollheim, Ashif Abir, Lara Munro), and the National Ecological Observatory Network (Keli Goodman, Kaelin Cawley) in Boulder, Colorado last week! After ~2 years of zoom meetings, this was the first time we were all able to meet together in person! It was a fantastic few days of research updates, discussing knowledge gaps related to landscape carbon cycling, working through metabolism model checks, and sharing our goals for the next year of our NSF-Funded Macrosystems Biology Project. We also got to meet one of our study sites in person for the first time - Como Creek (some photos of our site visit + a group dinner and additional hike are below)! Thanks to everyone for a fantastic #MacroCO2 meet-up!

Our project is characterizing the fluxes and fate of terrestrial carbon that enters streams using data from five landscapes in Alaska, Washington, Colorado, Kansas, and Tennessee. We will use these data to develop soil, stream, and stream network models of carbon cycling, emissions, and export at the ecosystem, watershed, and continental scale. If you'll be looking for a postdoctoral research position in the near future and the topic of this research is of interest to you, we will be posting a call for applications soon.

2022-06-17 - Bretz receives Robert Patterson Scholarship

Kristen Bretz was awarded a Robert Patterson Scholarship from Virginia Tech's Department of Biological Sciences for the 2022-2023 academic year. From her award letter: "This scholarship is designated for graduate students in the Department of Biological Sciences who have demonstrated excellence in research and progress toward their degree. The Patterson scholarship was established in honor of Dr. Robert Patterson, a former department head and member of our department." Congratulations, Kristen!

2022-06-17 - López Lloreda awarded summer & 2022-2023 fellowships

Carla López Lloreda is working with Freshwater Future as a Yale Environmental Fellow this summer, and will transition from a Master's to a PhD program in Fall 2022 as a 2022-2023 Global Change Center Diversity Fellow. Congratulations, Carla! We're excited to learn more about your summer fellowship when you return in the fall and we're so glad you'll be working with us a Virginia Tech for a while longer!

2022-06-10 - Hotchkiss receives tenure & promotion

Virginia Tech's Board of Visitors voted to approve Erin Hotchkiss' tenure and promotion to Associate Professor in the Department of Biological Sciences! The full list of all promotions (including several fantastic colleagues in Biological Sciences and The Global Change Center - congrats to everyone!) is here:

2022-06-01 - Photos from the field: Coweeta, NC

Erin recently returned from Virginia Tech's final Coweeta Hydrologic Lab field campaign of our NSF-funded stream warming project! We monitored an experimentally warmed and a reference stream to test how increasing temperatures may alter carbon fluxes and fate in headwater stream networks. Now that the dissolved oxygen sensors are out of the stream and our field measurements have concluded, we'll be finalizing our two-station, whole-stream metabolism model to assess multi-annual patterns in photosynthesis and respiration (i.e., metabolism), and will compare ecosystem metabolism rates between the warmed / reference stream before and during the whole-stream warming experiment.

2022-05-14 - Hotchkiss Lab at #JASM22!

2020-06-01: Update with a few lab photos from the conference! Thanks to everyone who helped make JASM such a fun and energizing meeting!

Top: Kristen Bretz & Carla López Lloreda presenting their posters. Bottom: JASM22 lab photo (Carla, Erin, Stephen, & Kristen) & Stephen Plont giving his talk.
Virginia Tech Stream Team happy hour / reunion! Photo of a subset of current & past Stream Team members, including current mentees of Stream Team alumni, at JASM22.

After two years of virtual meetings, we are excited to celebrate all things aquatic science at this year's Joint Aquatic Sciences Meeting! Below are poster, talk, and event highlights from our lab and collaborators.

2022-05-11 - Congratulations to our VT 2022 graduates!

Natalie Murphy (Biochemistry) and Felicity DeToll (Environmental Science) are graduating from Virginia Tech with their Bachelor's degrees this month!

Natalie has conducted research with our lab since 2019, and will be kicking off her post-graduation career as a STEM2VA intern with Capra Biosciences. Felicity conducted research with our lab as a Fralin Summer Research Fellow in 2021.

Congratulations on your graduation! We're excited to see what comes next for you both!

2022-04-20 - Gavriel Cambridge receives 2022 VWRRC Grant

Gavriel Cambridge, an undergraduate researcher working with Cully Hession (Biological Systems Engineering), Carla López Lloreda, and Erin Hotchkiss, was awarded research funding through the 2022 Virginia Water Resources Research Center's (VWRRC) Student Competitive Grant Program! His proposal was titled "Hydrologic and Biogeochemical Impacts of Beaver Activity on Stream Restoration".

Gavriel will test how beaver activity in Stroubles Creek is altering water levels, stream-floodplain connections, sediment transport, and biogeochemistry (e.g., dissolved oxygen, organic carbon, nutrients, and greenhouse gas emissions). He is also interested in linking the consequences of beaver activity with stream restoration goals. Stroubles Creek is designated as an impaired waterway due to high sediment loads, and has thus been an active site for riparian tree restoration and in-stream monitoring efforts. The recent increase in beaver activity in and near local streams is an exciting new development for our research group's work in the Stroubles Creek watershed (O'Donnell & Hotchkiss 2019, 2022; Lakoba et al. 2021; Plont et al. 2022), and we are thrilled to see Gavriel's vision for research supported by this competitive research grant. Congratulations, Gavriel!

Gavriel Cambridge taking a sample from Stroubles Creek, Blacksburg, Virginia.

2022-03-29 - Research led by Bretz featured in VT News

A recent Virginia Tech news article highlighted PhD candidate Kristen Bretz's research on carbon emissions from mountain stream corridors in collaboration with past undergraduate researchers in the lab Alexis Jackson, Sumaiya Rahman, and Jonathon Monroe! This project and Kristen's ongoing dissertation research is funded by the National Science Foundation with additional support from Virginia Tech's Global Change Center (Monroe, Jackson), the Society for Freshwater Science (Bretz), and the Virginia Water Resources Research Center (Bretz).

You can read the VT news article co-authored by Kristen here:

The peer-reviewed paper that came from this collaboration is: Bretz, K.A., A.R. Jackson, S. Rahman, J.M. Monroe, & E.R. Hotchkiss. 2021. Integrating ecosystem patch contributions to stream corridor carbon dioxide and methane fluxes. Journal of Geophysical Research – Biogeosciences 126: e2021JG006313.

Kristen Bretz measuring greenhouse gas emissions from a mountain stream at Coweeta Hydrologic Lab in North Carolina.

2022-03-25 - López Lloreda receives Outstanding Master's Student Award

Carla López Lloreda was this year's Outstanding Master's Student in Virginia Tech's College of Science! Graduate student nominees from each department were evaluated based on the candidate's: excellence of academic performance and research; teaching success; honors and awards; and involvement in outreach activities and other professional service. Congratulations, Carla!

2022-05-11 Update:

Carla was recently featured in a VT News article about her award!

Carla López Lloreda and Erin Hotchkiss at Virginia Tech's 2022 Graduate Student Awards Ceremony.

2022-03-23 - López Lloreda receives SFS endowment award

Carla López Lloreda is one of this year's recipients of the Society for Freshwater Science (SFS) Endowment Award! This competitive award is given annually to top-ranked research proposals submitted by graduate student members of SFS. Carla's proposal was titled: "Integrating high-frequency carbon cycling and emissions dynamics in hydrologically dynamic wetland-dominated landscapes".

Carla López Lloreda sampling one of her study sites, a headwater wetland on the Delmarva peninsula of Maryland.
Chamber used to measure wetland greenhouse gas emissions to the atmosphere (left) and in situ dissolved oxygen sensor (right) at one of Carla's Delmarva study sites in Maryland.

2022-03-15 - Plont leads new article published in JGRB

Stephen Plont recently published the second chapter of his dissertation, "Integrating Perspectives on Dissolved Organic Carbon Removal and Whole-Stream Metabolism" in the Journal of Geophysical Research - Biogeosciences! Stephen's paper was co-authored with a former undergraduate researcher in our lab Jacob Riney (VT 2020) and Erin Hotchkiss.

Citation: Plont, S., Riney, J., & Hotchkiss, E. R. (2022). Integrating perspectives on dissolved organic carbon removal and whole-stream metabolism. Journal of Geophysical Research: Biogeosciences 127: e2021JG006610.

2022-02-15 - O'Donnell & Hotchkiss publish new article in Biogeosciences

Brynn O'Donnell and Erin Hotchkiss co-authored a paper published today in Biogeosciences: "Resistance and resilience of stream metabolism to high flow disturbances". This is the second chapter of O'Donnell's Master's thesis conducted with Hotchkiss at Virginia Tech, which builds on her first data paper (Coupling Concentration- and Process-Discharge Relationships Integrates Water Chemistry and Metabolism in Streams) and was part of the inspiration for her popular science communication article about Ghost Streams.

Paper Summary: "A stream is defined by flowing water, but higher flow from storms is also a frequent disturbance. This paper tests how higher flow changes stream metabolism (respiration and photosynthesis, R and P). P was less resistant to changes in flow compared to R, and P took longer to recover from storms than R (2.5 versus 1.1 days). Further work on metabolic responses to flow disturbance is critical given projected increases in storms and the influence of higher flows on ecosystem health and functioning."

Citation: O’Donnell, B. & E.R. Hotchkiss. 2022. Resistance and resilience of stream metabolism to high flow disturbances. Biogeosciences 19: 1111-1134. doi: 10.5194/bg-19-1111-2022.

2022-02-15 - Pérez Rivera participates in Women in Science panel

Katherine X. Pérez Rivera participated in an invited panel held by the U.S. Embassy Prague for the 2022 International Day of Women and Girls in Science: "Career as a scientist - woman and their stories". Katherine is a Fulbright Fellow in the Czech Republic this year, where she is collaborating with scientists at the Czech Geological Survey (Česká geologická služba) on a project quantifying dissolved organic matter and ecosystem metabolism dynamics in streams recovering from acid deposition.

2022-01-20 - López Lloreda selected member of 2022 SWS Mentoring Program

Carla López Lloreda was selected to participate in the 2022 Society of Wetland Scientists Multicultural Mentoring Program (SWaMMP). Participants in the program receive a $1000 travel award to support their attendance at the 2022 Joint Aquatic Sciences Meeting (JASM). Congratulations, Carla!