Marine biogeochemistry · Ocean fertility · Earth systems
Tracing causal chains from trace elements to ocean life.
I am a marine biogeochemist studying how trace-metal micronutrients shape microbial ecosystems and regulate nutrient and carbon cycling in the ocean. My work brings together analytical chemistry, field oceanography, and experimental approaches to understand ocean fertility in a changing Earth system.
01 / Perspective
My research is driven by a central question: how does the chemistry of the Earth system shape the chemistry of life and vice versa?
I bring over a decade of analytical expertise to assess the impact of trace elements on marine microbial communities and nutrient and carbon cycling. I am currently interested in micronutrient bioavailability as a means to better understand ocean fertilization.
I favor multiple working hypotheses over premature optimization.
02 / Questions & methods
I investigate how micronutrient supply, chemical speciation, and biological demand influence marine microbial communities, primary production, and carbon cycling. My current work connects natural fertilization processes to questions about ocean-based climate interventions and their ecological consequences.
Trace metals and bioavailability. Iron, manganese, copper, and the chemical forms that regulate their biological accessibility.
Ocean fertility and carbon. Nitrogen fixation, microbial ecology, biological carbon export, and responsible evaluation of ocean fertilization.
Earth-surface connections. Glacial and hydrothermal sources of micronutrients, isotope geochemistry, and climate-sensitive changes in supply.
03 / Roles & leadership
Current
Nitrogen Fixation for Phytoplankton Carbon (NFPC) · South Pacific
I advocate for rigorous science, support interdisciplinary researchers, and help build scientific partnerships and research capacity in the South Pacific. Our work investigates natural iron-driven nitrogen fixation and its implications for ocean fertility and carbon cycling.
2024–present
University of Southern California · Wrigley Institute / Department of Earth Sciences
Research on trace-metal chemical speciation and bioavailability, with applications to marine microbial processes and ocean carbon cycling.
2021–2024
Scripps Institution of Oceanography, UC San Diego · J. Craig Venter Institute
Led independent NSF-funded investigations of glacially derived iron, isotope geochemistry, and the biological availability of particulate micronutrients.
2012–2014
Rutgers University · Plasma-source mass spectrometry
04 / Academic background
Ph.D., Oceanography · UC San Diego
2021 · Scripps Institution of Oceanography
Iron sources, sinks, and cycling in productive coastal seas · Katherine Barbeau
M.S., Oceanography · UC San Diego
2016
B.A., Chemistry · Oberlin College
2012
NSF Postdoctoral Research Fellowship in Ocean Sciences; NSF Graduate Research Fellowship; Edna Baily Sussman Trust Special Merit Award; Antarctic Service Medal.
265 days at sea across the Antarctic Peninsula, Southern Ocean, California Current, and other coastal and open-ocean settings, alongside chief scientist leadership of Alaskan fjord fieldwork.
Instructor of Record in Perspectives on Ocean Science; teaching assistant in Life and Climate and Introduction to Geochemistry; mentorship of undergraduate researchers; scientific peer review and public outreach.
05 / Published research
Peer-reviewed publications listed by year. Selected first-author papers include a manuscript thumbnail beside the citation; click a thumbnail to open the PDF, or use the DOI link to visit the publisher.
Tidewater glacier dynamics shape the geochemistry of glacial sediment plumes.Forsch, K. O., Ruacho, A., & Aarons, S. M. Tidewater cycle drives alpine glacial sediment plume geochemistry. Nature Communications, 16, 9211.
Gangrade, S., Franks, P. J. S., Forsch, K. O., & Barbeau, K. A. Salinity is diagnostic of maximum potential chlorophyll and phytoplankton community structure in an Eastern Boundary Upwelling System. Limnology and Oceanography Letters.
Stow, P. R., Forsch, K. O., Thomsen, E., Naka, H., Haygood, M. G., Barbeau, K. A., & Butler, A. Stereospecific control of microbial growth by a combinatoric suite of chiral siderophores. Proceedings of the National Academy of Sciences, 122(10), e2423730122.
Sedlak, J. A., Vishnoi, M., Forsch, K. O., Bhadha, P., Aarons, S. M., & Grassian, V. H. Probing interactions at the organic-inorganic interface of biomass burning aerosol: Reactivity of organic tracer species with different iron oxide mineral phases. ACS Earth and Space Chemistry.
Manck, L. E., Coale, T. H., Stephens, B. M., Forsch, K. O., Aluwihare, L. I., Dupont, C. L., Allen, A. E., & Barbeau, K. A. Iron limitation of heterotrophic bacteria in the California Current system tracks relative availability of organic carbon and iron. The ISME Journal, wrae061.
Huang, L., Tissot, F., Ibanez-Mejia, M., Forsch, K. O., et al. High-precision zirconium isotope analysis of Pacific seawater reveals large mass-dependent fractionations in the ocean. Geochimica et Cosmochimica Acta.
Lampe, R. H., Coale, T. H., Forsch, K. O., et al. Short-term acidification promotes diverse iron acquisition and conservation mechanisms in upwelling-associated phytoplankton. Nature Communications, 14, 7215.
Iron limitation influences biogeochemical processes in coastal upwelling filaments.Forsch, K. O., Fulton, K. C., Weiss, M. M., Krause, J. W., Stukel, M. R., & Barbeau, K. A. Iron limitation and biogeochemical effects in southern California Current coastal upwelling filaments. Journal of Geophysical Research: Oceans, 128, e2023JC019961.
Fjord meltwaters supply iron and manganese to coastal Antarctic phytoplankton.Forsch, K. O., Hahn-Woernle, L., Sherrell, R. M., Roccanova, J., Bu, K., Burdige, D., Vernet, M., & Barbeau, K. A. Seasonal dispersal of fjord meltwaters as an important source of iron and manganese to coastal Antarctic phytoplankton. Biogeosciences.
Pan, B. J., Vernet, M., Manck, L., Forsch, K., Ekern, L., Mascioni, M., Barbeau, K. A., Almandoz, G. O., & Orona, A. J. Environmental drivers of phytoplankton taxonomic composition in an Antarctic fjord. Progress in Oceanography, 183, 102295.
Sherrell, R. M., Lagerström, M., Forsch, K. O., Stammerjohn, S. E., & Yager, P. L. Dynamics of dissolved iron and other bioactive trace metals (Mn, Ni, Cu, Zn) in the Amundsen Sea Polynya, Antarctica. Elementa, 3, 71.
In preparation
Forsch, K. O., & John, S. New application of chelating resin beads to probe cadmium and lead kinetic speciation in seawater. Manuscript in preparation.
In preparation
Steck, V., Forsch, K. O., Barbeau, K. A., & Diaz, J. A novel role for manganese in phytoplankton phosphorus nutrition in the ocean. Manuscript in preparation; Steck and Forsch listed as co-first authors.
In preparation
Forsch, K. O., Yang, S. C., John, S., et al. A hidden reservoir of isotopically distinct copper in the Pacific Ocean. Manuscript in preparation; Forsch and Yang listed as co-first authors.
Under review
Forsch K. O., Barbeau K. A., Stukel M., Chabert P., Appelgate A. Inorganic nutrient transport and limitation in the California Current Ecosystem. Under review at BioScience.
Under review
Steck, V., Lampe, R. H., Bhakta, S., Marrufo, K. C., Adams, J. C., Sachdev, E., Forsch, K. O., Barbeau, K. A., Allen, A. E., & Diaz, J. M. Atypical phosphatases drive dissolved organic phosphorus utilization by phosphorus-stressed phytoplankton in the California Current Ecosystem. Under review at The ISME Journal.
06 / Connect
I welcome conversations about marine biogeochemistry, field collaborations, ocean fertility, and interdisciplinary research in the South Pacific.
forsch@usc.edu