Dr. Darci Swenson Perger, Ph.D., 2024
Darci’s dissertation focused on iron cycling in bioturbated sediments. At present, the estimate of marine sediments as a source of iron to the ocean is not well constrained given the complexity of sedimentary environments. Supported by an NSF funded grant
, Darci investigated how depositional conditions such as sediment type, bioturbation regime, and oxygen availability affect the flux of iron out of sediments, and particularly the isotopic signature of the iron being released. She also investigated the isotopic signature of the iron released in a variety of depositional conditions as a means of tracking and quantifying oceanic iron that was sourced from sediments.
Darci was the recipient of the 2024 Nuria Protopopescu Memorial Teaching Award. This award is presented annually to a SoMAS graduate student based on demonstrated excellence in teaching, innovation and creativity in instructional plans and materials, and engagement with and dedication to their students.
Darci is currently a Lecturer at Coastal Carolina University.
Publications
Dwyer, I.P., Swenson Perger, D.A., Graffam, M., Aller, R.C., Wehrmann, L.M. and Volkenborn, N., 2024. Seasonality of bioirrigation by the maldanid polychaete Clymenella torquata and related oxygen dynamics in permeable sediments. J. Exp. Mar. Biol. Ecol. 572, 151987.
Swenson Perger, D.A., Dwyer, I.P., Aller, R.C., Volkenborn, N., Heilbrun, C. and Wehrmann, L.M., 2023. Seasonal iron fluxes and iron cycling in sandy bioirrigated sediments. Frontiers in Marine Science 10.
Dr. Lisa Herbert, Ph.D., 2020
Lisa studies the biogeochemistry of trace metals such as Fe, Mn, Cd, Co, Cu, Mo, Ni, and U in marine sediments. Her dissertation research at SoMAS investigated the biogeochemical cycling of trace metals in sediments of glacially impacted fjords on Svalbard, an Arctic island north of Norway. In particular, her work focused on a) how cryptic sulfur cycling may control trace metal behavior even in the fjord sediments that are dominated by iron and manganese reduction, b) how local glacier activity (i.e. surging or retreating) may influence the balance of Fe/Mn and sulfur cycling and by extension the sequestration or release of trace metals, c) the spatial and temporal dynamics of benthic Fe fluxes in Svalbard fjords. Lisa was also a fellow in the STRIDE (Science Training and Research to Inform Decision) Program.
Lisa is now a Rutgers University EOAS Institute Postdoctoral Program Awardee.
Publications
Herbert, L.C., Michaud, A.B., Laufer-Meiser, K., Hoppe, C.J.M., Zhu, Q., Aller, R.C., Jørgensen, B.B., and Wehrmann, L.M., 2022. Tight benthic-pelagic coupling drives seasonal and interannual changes in iron‑sulfur cycling in Arctic fjord sediments (Kongsfjorden, Svalbard). Journal of Marine Systems 103645.
Herbert, L.C., Zhu, Q., Michaud, A.B., Laufer, K., Jones, C.K., Riedinger, N., Stooksbury, Z.S., Aller, R.C., Jørgensen, B.B., and Wehrmann, L.M., 2021. Benthic iron flux influenced by climate-sensitive interplay between organic carbon availability and diagenetic mineral formation in Arctic fjords. Limnology and Oceanography 66:9, 3374-3392.
Herbert, L., Riedinger N., Aller R. J., Jørgensen B. B., Michaud, A. B., Laufer, K., Røy, H., Wehrmann L. M., 2020. Early diagenesis of trace metals in modern fjord sediments of the high Arctic. Geochimica Cosmochimica Acta 271, 33-60.
Buongiorno, J., Herbert, L.C., Wehrmann, L.M., Michaud, A.B., Laufer, K., Røy, H., Jørgensen, B.B., Szynkiewicz, A., Faiia, A., Yeager, K.M., Schindler, K. and Lloyd, K.G., 2019. Complex Microbial Communities Drive Iron and Sulfur Cycling in Arctic Fjord Sediments. Applied and Environmental Microbiology, 85(14): e00949-19.
Wehrmann, L.M., Riedinger, N., Brunner, B., Kamyshny, A., Hubert, C. R. J., Herbert, L., Brüchert, V., Jørgensen, B. B., Ferdelman, T. G., Formolo, M. J., 2017. Iron-controlled oxidative sulfur cycling recorded in the distribution and isotopic composition of sulfur species in glacially influenced fjord sediments of west Svalbard. Chemical Geology, 466, pp.678–695.
Ashley Braunthal, M.Sc., 2020
Ashley studied paleo-redox conditions recorded in laminated sediments of Bowers Ridge Site U1342, Bering Sea, drilled during IODP Expedition 323. Her project focused on characterizing the relationship between past sedimentary redox conditions, water column ventilation, and surface water productivity.
Ashley is now a PhD student at the Institute of Environmental Science and Technology at the Universitat Autònoma de Barcelona. Her work contributes to the 2018 ERC Advanced Grant PALADYN project (New geochemical approach to reconstruct tropical palaeo-atmospheric dynamics).
Jeanette (Lee) Kao, M.Sc., 2017
Jeanette investigated the biogeochemical transformation of phosphorous in novel septic system technologies, including the removal of phosphorous through soil adsorption and precipitation and the interconnections between phosphorous and nitrogen cycling in these systems. This project was carried out in collaboration with the New York State Center for Clean Water Technology.
Jeannette is now a UX Designer at Esri.
Publications
Wehrmann, L.M., Lee, J.A., Price, R.E., Heufelder, G., Walker, H.W., and Gobler, C.J., 2020. Biogeochemical sequestration of phosphorus in a two-layer lignocellulose-based soil treatment system. Journal of Sustainable Water in the Built Environment 6(2):04020002.