Dr. Claudia Bergen

Sun, Xin, Frey, Claudia, McCoy, Daniel, Spieler, Matthias B A, Kelly, Colette L., Maloney, Ashley E., Garcia-Robledo, Emilio, Lehmann, Moritz F., Ward, Bess B., & Zakem, Emily J. (2025). Mechanistic understanding of nitrate reduction as the dominant production pathway of nitrous oxide in marine oxygen minimum zones. Nature Communications, 16. https://doi.org/10.1038/s41467-025-63989-9

Richardson, Christina M., Peucker-Ehrenbrink, Bernhard, Wyatt, Shea, Bourbonnais, Annie, Hatje, Vanessa, Frey, Claudia, Sanders, Tina, Varela, Diana E., & Paytan, Adina. (2025). Effects of climate change on river and groundwater nutrient inputs to the coastal ocean. Communications Earth & Environment, 6(1). https://doi.org/10.1038/s43247-025-02594-6

Frey, Claudia, Tang, Weiyi, Ward, Bess B., & Lehmann, Moritz F. (2024). Sample preservation methods for nitrous oxide concentration and isotope ratio measurements in aquatic environments [Journal-article]. Limnology and Oceanography: Methods, 22(10), 771–788. https://doi.org/10.1002/lom3.10638

Kelly, Colette L., Travis, Nicole M., Baya, Pascale Anabelle, Frey, Claudia, Sun, Xin, Ward, Bess B., & Casciotti, Karen L. (2024). Isotopomer labeling and oxygen dependence of hybrid nitrous oxide production [Journal-article]. Biogeosciences, 21(14), 3215–3238. https://doi.org/10.5194/bg-21-3215-2024

Huang, K., Eschenbach, W., Wei, J., Hausherr, D., Frey, C., Kupferschmid, A., Dyckmans, J., Joss, A., Lehmann, M. F., & Mohn, J. (2023). Simultaneous 15N Online Analysis in NH4+, NO2-, NO3-, and N2O to Trace N2O Production Pathways in Nitrogen-Polluted Aqueous Environments. ACS ES and T Water, 3(11), 3485–3495. https://doi.org/10.1021/acsestwater.3c00216

Choisnard, N., Burtscher, E., Forster, S., Frey, C., Moros, M., & Voss, M. (2023). The Amazon shelf sediments, a reactor that fuels intense nitrogen cycling at the seabed. Limnology and Oceanography, 68(10), 2211–2226. https://doi.org/10.1002/lno.12416

Tracey, J. C., Babbin, A. R., Wallace, E., Sun, X., Durussel, K. L., Frey, C., Martocello Iii, D. E., Tamasi, T., Oleynik, S., & Ward, B. B. (2023). All about nitrite: exploring nitrite sources and sinks in the eastern tropical North Pacific oxygen minimum zone. Biogeosciences, 20(12), 2499–2523. https://doi.org/10.5194/bg-20-2499-2023

Kelly, C. L., Manning, C., Frey, C., Kaiser, J., Gluschankoff, N., & Casciotti, K. L. (2023). Pyisotopomer: A Python package for obtaining intramolecular isotope ratio differences from mass spectrometric analysis of nitrous oxide isotopocules. Rapid Communications in Mass Spectrometry, 37(11). https://doi.org/10.1002/rcm.9513

Sun, X., Frey, C., & Ward, B. B. (2023). Nitrite Oxidation Across the Full Oxygen Spectrum in the Ocean. Global Biogeochemical Cycles, 37(4). https://doi.org/10.1029/2022gb007548

Einbock, Annika, Burtscher, Emma, Frey, Claudia, & Conen, Franz. (2023). Export of ice-nucleating particles from watersheds: results from the Amazon and Tocantins river plumes. Royal Society Open Science, 10(2), 220878. https://doi.org/10.1098/rsos.220878

Frey, Claudia, Sun, Xin, Szemberski, Laura, Casciotti, Karen L., Garcia-Robledo, Emilio, Jayakumar, Amal, Kelly, Colette, Lehmann, Moritz F., & Ward, Bess B. (2023). Kinetics of nitrous oxide production from ammonia oxidation in the Eastern Tropical North Pacific. Limnology and Oceanography, 68(2), 424–438. https://doi.org/10.1002/lno.12283

Tischer, Jana, Zopfi, Jakob, Frey, Claudia, Magyar, Paul M., Brand, Andreas, Oswald, Kirsten, Jegge, Corinne, Frame, Caitlin H., Miracle, María R., Sòria-Perpinyà, Xavier, Vicente, Eduardo, & Lehmann, Moritz F. (2022). Isotopic signatures of biotic and abiotic N2O production and consumption in the water column of meromictic, ferruginous Lake La Cruz (Spain). Limnology and Oceanography, 67(8), 1760–1775. https://doi.org/10.1002/lno.12165

Visser, Anna-Neva, Wankel, Scott D. D., Frey, Claudia, Kappler, Andreas, & Lehmann, Moritz F. (2022). Unchanged nitrate and nitrite isotope fractionation during heterotrophic and Fe(II)-mixotrophic denitrification suggest a non-enzymatic link between denitrification and Fe(II) oxidation. Frontiers in Microbiology, 13, 927475. https://doi.org/10.3389/fmicb.2022.927475

Sun, X., Frey, C., Garcia-Robledo, E., Jayakumar, A., & Ward, B. B. (2021). Correction: Microbial niche differentiation explains nitrite oxidation in marine oxygen minimum zones (The ISME Journal, (2021), 15, 5, (1317-1329), 10.1038/s41396-020-00852-3). ISME Journal, 15(8). https://doi.org/10.1038/s41396-021-01032-7

Bourbonnais, Annie, Frey, Claudia, Sun, Xin, Bristow, Laura A., Jayakumar, Amal, Ostrom, Nataniel E., Casciotti, Karen L., & Ward, Bess B. (2021). Protocols for assessing transformation rates of nitrous oxide in the water column. Frontiers in Marine Science, 8, 293. https://doi.org/10.3389/fmars.2021.611937

Sun, Xin, Frey, Claudia, Garcia-Robledo, Emilio, Jayakumar, Amal, & Ward, Bess B. (2021). Microbial niche differentiation explains nitrite oxidation in marine oxygen minimum zones. The ISME Journal, 15(5), 1317–1329. https://doi.org/10.1038/s41396-020-00852-3

Frey, Claudia, Bange, Hermann W., Achterberg, Eric P., Jayakumar, Amal, Löscher, Carolin R., Arévalo-Martínez, Damian L., León-Palmero, Elizabeth, Sun, Mingshuan, Sun, Xin, Xie, Ruifang C., Oleynik, Sergey, & Ward, Bess B. (2020). Regulation of nitrous oxide production in low-oxygen waters off the coast of Peru. Biogeosciences, 17(8), 2263–2287. https://doi.org/10.5194/bg-17-2263-2020

Wilson, Samuel T., Al-Haj, Alia N., Bourbonnais, Annie, Frey, Claudia, Fulweiler, Robinson W., Kessler, John D., Marchant, Hannah K., Milucka, Jana, Ray, Nicholas E., Suntharalingam, Parvadha, Thornton, Brett F., Upstill-Goddard, Robert C., Weber, Thomas S., Arévalo-Martínez, Damian L., Bange, Hermann W., Benway, Heather M., Bianchi, Daniele, Borges, Alberto V., Chang, Bonnie X., et al. (2020). Ideas and perspectives: A strategic assessment of methane and nitrous oxide measurements in the marine environment. Biogeosciences, 17(22), 5809–5828. https://doi.org/10.5194/bg-17-5809-2020

Cojean, A. N. Y., Zopfi, J., Gerster, A., Frey, C., Lepori, F., & Lehmann, M. F. (2019). Direct O-2 control on the partitioning between denitrification and dissimilatory nitrate reduction to ammonium in lake sediments. Biogeosciences, 16(23), 4705–4718. https://doi.org/10.5194/bg-16-4705-2019

Ji, Qixing, Frey, Claudia, Sun, Xin, Jackson, Melanie, Lee, Yea-Shine, Jayakumar, Amal, Cornwell, Jeffrey C., & Ward, Bess B. (2018). Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay. Biogeosciences, 15(20), 6127–6138. https://doi.org/10.5194/bg-15-6127-2018

Wannicke, Nicola, Frey, Claudia, Law, Cliff S., & Voss, Maren. (2018). The response of the marine nitrogen cycle to ocean acidification. Global Change Biology, 24(11), 5031–5043. https://doi.org/10.1111/gcb.14424

Frey, C., Hietanen, S., Jürgens, K., Labrenz, M., & Voss, M. (2014). N and O isotope fractionation in nitrate during chemolithoautotrophic denitrification by Sulfurimonas gotlandica. Environmental Science and Technology, 48(22), 13229–13237. https://doi.org/10.1021/es503456g

Korth, F., Deutsch, B., Frey, C., Moros, C., & Voss, M. (2014). Nitrate source identification in the Baltic Sea using its isotopic ratios in combination with a Bayesian isotope mixing model. Biogeosciences, 11(17), 4913–4924. https://doi.org/10.5194/bg-11-4913-2014

Frey, C., Dippner, J. W., & Voss, M. (2014). Close coupling of N-cycling processes expressed in stable isotope data at the redoxcline of the Baltic Sea. Global Biogeochemical Cycles, 28(9), 974–991. https://doi.org/10.1002/2013GB004642

Voss, Maren, Choisnard, Noémie, Bartoli, Marco, Bonaglia, Stefano, Bourbonnais, Annie, Frey, Claudia, Holtermann, Peter, Jennerjahn, Tim C., Jickells, Tim, & Weston, Keith. (2024). Coastal Nitrogen Cycling – Biogeochemical Processes and the Impacts of Human Activities and Climate Change. In Daniel Baird and Michael Elliot (ed.), Treatise on Estuarine and Coastal Science (Second edition, pp. 225–250). Academic Press is an imprint of Elsevier. https://doi.org/10.1016/b978-0-323-90798-9.00042-1

Dangl, G., Frey, C., Hassenrück, C., Sabbaghzadeh, B., Wäge‐Recchioni, J., Lehmann, M. F., Schulz‐Vogt, H., Fabian, J., Ley, M., Rehder, G., & Jürgens, K. (2025). Processes and microorganisms driving nitrous oxide production in the Benguela Upwelling System [Journal-article]. Limnology and Oceanography, 70(4), 850–869. https://doi.org/10.1002/lno.12811

Tischer, J., Zopfi, J., Frey, C., Venetz, J., Giglio, E., Burgdorfer, L., Rehmann, O., Wankel, S. D., & Lehmann, M. F. (2025). Nitrogen and oxygen isotope effects during enzymatic nitrate reduction in vitro and by natural lake water consortia [Posted-content]. Cold Spring Harbor Laboratory. https://doi.org/10.1101/2025.03.29.645582