• Associate Professor
Jessica Fitzsimmons


The Fitzsimmons Lab is recruiting curious and motivated undergraduate and PhD students and postdocs to start in 2022! We value diverse perspectives, talents, and identities that we consider essential to broadening the scientific and societal impact of our science. Please contact jessfitz@tamu.edu with a copy of your CV for more information.

  • Trace metal biogeochemistry
  • Colloids and metal speciation
  • Metal stable isotopes
  • Hydrothermal vent biogeochemistry
  • Polar Oceanography
  • Inductively-Coupled Plasma Mass Spectrometry
  • Analytical chemistry
  • Inorganic Chemical Oceanography


Fitzsimmons is a chemical oceanographer interested in the biogeochemical cycling of trace metals in the ocean. Trace metals are important to study because they can act as (1) nutrients for marine organisms, (2) anthropogenic pollutants, and/or (3) tracers for oceanographic processes. Metals such as iron, copper, manganese, zinc, cadmium, and nickel are required nutrients for photosynthesizing plankton (phytoplankton), who sit at the base of the marine food web and contribute to the removal of carbon dioxide from the atmosphere. However, trace metals are present in very low concentrations in seawater, and as a result some metals (iron being the best example) have been shown to limit the growth of phytoplankton in more than a third of the global surface ocean. We know that phytoplankton are an integral part of the global carbon cycle and heavily influence the feedback cycles of earth's climate both today and during the geologic past. Thus, trace metals play an important role in global carbon cycling and thus global climate, making it an important topic of study in the face of modern climate change.

The Fitzsimmons group studies the distribution, physicochemical speciation, and isotope ratios of trace metals in seawater in order to better understand the cycles and biological usage of metals in the water column. We are a sea-going group, collecting our samples at sea and then analyzing them back in the laboratory. Our primary analytical tool is inductively coupled plasma mass spectrometry (ICP-MS), which is housed in the Williams Radiogenic Laboratory at Texas A&M. However, biogeochemistry is, by its very name, an interdisciplinary field and thus we evaluate all trace metal processes in close cooperation with other labs measuring the biological, geological, and physical parameters of our study regions, which frames our interpretation in the context of the global ocean system.



OCNG 251 – Oceanography

OCNG 453 – Hydrothermal Vents & Mid-Ocean Ridges

OCNG 640 – Chemical Oceanography

OCNG 641 – Inorganic Aquatic Geochemistry


Current Students:

  1. Janelle Steffen (Ph.D. student)
  2. Nathan Lanning (Ph.D. student)
  3. Shelby Gunnells (Ph.D. student)
  4. Yerim Kim (Ph.D. student)

Educational Background

  • Ph.D. Chemical Oceanography, MIT/WHOI Joint Program, 2013.
  • B.A. Chemistry, Biology with a concentration in Marine Science, Boston University, 2008.

Research Interests

  • Chemical Oceanography: Trace metal biogeochemistry, nutrients, pollutants, colloids, isotopes, hydrothermal vents, polar oceanography

Awards & Honors

  • 2021 – International Association of the Physical Sciences of the Oceans (IAPSO) Early Career Award in the Chemical Ocean Sciences
  • 2020 - Texas A&M College of Geosciences Dean’s Distinguished Award for Faculty Service
  • 2019 – National Academy of Sciences, Gulf Research Program, Early-Career Fellowship
  • 2014 – Rossby Award for Best Dissertation in the MIT Programs in Atmospheres Oceans & Climate
  • 2011-2012 – MIT Martin Family Society Fellowship for Sustainability
  • 2009-2012 – NSF Graduate Research Fellowship
  • 2008-2009 – MIT Presidential Fellowship
  • 2006 – Ernest F. Hollings Scholarship & Internship, NOAA

Selected Publications

    • Jensen, LT, Lanning, NT, Marsay, CM, Buck, CS, Aguilar-Islas, A, Rember, R, Landing, WJ, Sherrell, RM, and Fitzsimmons, JN (2021). Biogeochemical cycling of colloidal trace metals in the Arctic cryosphere. Journal of Geophysical Research: Oceans, Special Issue on Arctic Ocean. 126, e2021JC0177394. doi: 1029/2021JC017394.
    • Lopez, AM, Brandon, AD, Ramos, RC, Fitzsimmons, JN, Dellapenna, TM, and Adams, HM (2021) Lead geochemistry of sediments in Galveston Bay, Texas. Environmental Advances, 4: 100057 doi: 1016/j.envadv.2021.100057.
    • Hoffman, CL, Schladweiler, C, Seaton, NCA, Nicholas, SL, Fitzsimmons, JN, Sherrell, RM, German, CR, Lam, PJ, and Toner, BM (2020). Diagnostic morphology and solid-state chemical speciation of hydrothermally derived particulate Fe in a long-range dispersing plume. ACS Earth & Space Chemistry, Special Issue on Marine Particles. 4: 1831-1842. doi: 1021/acsearthspacechem.0c00067.
    • Jensen, LT, Morton, P, Twining, BS, Heller, MI, Hatta, M, Measures, CI, John, SG, Zhang, R, Sherrell, RM, and Fitzsimmons, JN (2020). A comparison of marine Fe and Mn cycling: U.S. GEOTRACES GN01 Western Arctic case study. Geochimica et Cosmochimica Acta. doi: 1016/j.gca.2020.08.006.
    • Jenkins, WJ, Hatta, M, Fitzsimmons, JN, Schlitzer, Lanning, NT, R, Shiller, A, Buckley, NR, German, CR, Lott III, DE, Weiss, G, Whitmore, L, Casciotti, K, Lam, PJ, Cutter, GA, Cahill, KL (2020). An intermediate-depth source of hydrothermal 3He and dissolved iron in the North Pacific. Earth and Planetary Science Letters, 539: 116223. doi: 1016/j.epsl.2020.116223.
    • Charette, MA, Kipp, LE, Jensen, LT, Dabrowski, JS, Whitmore, LM, Fitzsimmons, JN, Williford, T, Ulfsbo, A, Jones, E, Bundy, RM, Vivancos, SM, Pahnke, K, John, SG, Xiang, Y, Hatta, M, Petrova, M, Heimburger-Bovaida, L-E, Bauch, D, Newton, R, Pasqualini, A, and more than 40 other authors listed alphabetically (2020). The Transpolar Drift as a source of riverine and shelf-derived trace elements to the Central Arctic Ocean. Journal of Geophysical Research: Oceans, 125: e2019JC015920. doi: 1029/2019JC015920.
    • Kadko, D, Aguilar-Islas, A, Buck, C, Fitzsimmons, JN, Landing, WJ, Shiller, A, Till, CP, Bruland, KW, Boyle, EA, and Anderson, RF (2020). Sources, fluxes, and residence times of trace elements measured during the U.S. GEOTRACES East Pacific Zonal Transect. Marine Chemistry, 222: 103781. doi: 1016/j.marchem.2020.103781.
    • Hayes, CT, Fitzsimmons, JN, Jensen, LT, Lanning, NT, Hatta, M, McGee, D, and Boyle, EA. (2020) A Lagrangian view of trace elements and isotopes in the North Pacific. Journal of Geophysical Research: Oceans, 125, e2019JC015862. doi: 1029/2019JC015862.
    • Jensen, LT, Wyatt, NJ, Landing, WM, and Fitzsimmons, JN. (2020) Assessment of the stability, sorption, and exchangeability of marine colloidal metals. Marine Chemistry, 220: 103754. doi: 1016/j.marchem.2020./103754.
    • Carvalho, F, Fitzsimmons, JN, Couto, N, Gorbunov, M, Kohut, J, Oliver, MJ, Sherrell, RM, and Schofield, O (2020) Testing the Canyon Hypothesis: Evaluating light and nutrient controls of phytoplankton growth in penguin foraging hotspots along the West Antarctic Peninsula. Limnology & Oceanography, 65:455-470. doi: 1002/lno.11313.
    • Zhang, R, Jensen, LT, Fitzsimmons, JN, Sherrell, RM, and John, SG. (2019) Dissolved cadmium and cadmium stable isotopes in the western Arctic Ocean. Geochimica et Cosmochimica Acta, 258: 258-273. doi: 1016/j.gca.2019.05.028.
    • Jensen, LT, Wyatt, NJ, Twining, BS, Rauschenberg, S, Landing, WM, Sherrell, RM, and Fitzsimmons, JN (2019). Biogeochemical cycling of dissolved zinc in the Western Arctic (GEOTRACES GN01). Global Biogeochemical Cycles, 33. doi: 1029/2018GB005975.
    • Cheize, M, Planquette, H, Fitzsimmons, JN, Pelleter, E, , Sherrell, RM, Lambert, C, Bucciarelli, E, Sarthou, G, Boutorh, J, Le Goff, M, Liorzou, C, Cheron, S, Viollier, E, Gayet, N. (2019) Contribution of resuspended sediments to the dissolved trace metal pool: An experimental study. Chemical Geology, 511: 389-415. doi: 1016/j.chemgeo.2018.10.003.
    • Boiteau, RM, Till, CP, Coale, T, Fitzsimmons, JN, Bruland, KW, and Repeta (2019), D. Patterns of iron and siderophore distributions across the California Current System. Limnology & Oceanography, 64: 376-389. doi:1002/lno.11046.
    • Kadko, D, Aguilar-Islas, A, Bolt, C, Buck, CS, Fitzsimmons, JN, Jensen, LT, Landing, WM, Marsay, CM, Rember, R, Shiller, AM, Whitmore, LM, Anderson, RM. (2019) The residence time of trace elements determined in the surface Arctic Ocean during the 2015 US Arctic GEOTRACES expedition. Marine Chemistry, 208: 56-69. doi:1016/j.marchem.2018.10.011
    • Marsay, CM, Aguilar-Islas, A, Fitzsimmons, JN, Hatta, M, Jensen, LT, John, SG, Kadko, D, Landing, WM, Lanning, N, Morton, PL, Pasqualini, A, Rauschenberg, S, Sherrell, RM, Shiller, A, Twining, BS, Whitmore, L, Zhang, R, and Buck, CS (2018). Dissolved and particulate trace elements in Arctic melt ponds. Marine Chemistry, 204: 70-85. doi: 1016/j.marchem.2018.06.002
    • Schlitzer, R, et al. including hundreds of authors including Fitzsimmons, JN (2018). The GEOTRACES Intermediate Data Product 2017. Chemical Geology, 493: 210-223. doi:1016/j.chemgeo.2018.05.040
    • Sherrell, RM, Annett, AL, Fitzsimmons, JN, Roccanova, VJ, Meredith, MP (2018). A “shallow bathtub ring” of local sedimentary iron input maintains the Palmer Deep biological hotspot on the West Antarctic Peninsula shelf. Philosophical Transactions of the Royal Society A, 376 (2122): 20170171. doi: 1098/rsta.2017.0171
    • Hoffman, CL, Nicholas, SL, Ohnemus, DC, Fitzsimmons, JN, Sherrell, RM, German, CR, Lee, J-M, Lam, PJ, & Toner, BT (2018). Near-field iron and carbon chemistry of non-buoyant hydrothermal plume particles, Southern East Pacific Rise 15°S. Marine Chemistry, 201: 183-197. doi: 1016/j.marchem.2018.01.011
    • Mellet, T, Brown, MT, Chappell, PD, Duckham, C, Fitzsimmons, JN, Till, CE, Maldonado, M, Sherrell, RM, & Buck, KL (2018). The biogeochemical cycling of iron, copper, nickel, cadmium, manganese, and scandium in a California Current experimental study. Limnology & Oceanography. 63: S425-S447. doi: 1002/lno.10751
    • Fitzsimmons, JN, John, SG, Marsay, CM, Hoffman, C, Nicholas, S, Toner, BM, German, CR, and Sherrell, RM. (2017) Iron persistence in a distal hydrothermal plume supported by dissolved-particulate exchange. Nature Geoscience, 10: 195-201. doi: 10.1038/ngeo2900


    Active Projects: 

    1. Accelerating Thwaites Ecosystem Impacts for the Southern Ocean (ARTEMIS). NSF GEO-NERC 1941308 (8/21 – 7/24). Lead-PI: Tish Yager (UGA). Co-PIs: Rob Sherrell (Rutgers), Patricia Madeiros (UGA), Pierre St-Laurent (VIMS), Sharon Stammerjohn (UC-Boulder).

    Student: Janelle Steffen

    This project will investigate the biogeochemical impacts of glacial melt from the Thwaites glacier, Amundsen Sea, Antarctica, which is one of the fastest melting glaciers flowing from the West Antarctic Ice Sheet. The physical melting processes are being studied by the International Thwaites Glacier Collaboration (ITGC), including an ongoing oceanographic field program (TARSAN). ARTEMIS aims to use trace metal, nutrient, organic matter, and microorganism measurements to understand the impact of glacial melt on the coastal ecosystem and the regional carbon cycle. Specifically, the Fitzsimmons lab’s roles in ARTEMIS are to examine iron speciation (colloids) along the cruise transect and employ iron isotope measurements to understand the relative contributions of iron from deep water, benthic, and glacial melt sources, in order to develop a greater understanding of how iron is modified along the Antarctic coastal current.

    2. Understanding the impacts of deep-sea mining of manganese nodules on the pelagic ecosystem, Clarion Clipperton Zone (CCZ), Pacific Ocean, DeepGreen Metals, Inc. Lead-PI: Jeff Drazen (University of Hawaii). Co-PIs: Mariko Hatta and Chris Measures (University of Hawaii) and a host of others.

    Student: Shelby Gunnells

    This is a project funded by DeepGreen Metals to study the water column ecosystem of the NORI-D exploration region in the CCZ, both during baseline studies pre-mining and after mining trials. This project is an interdisciplinary collaboration, and our part will be study the chemical oceanography of the CCZ water column, including oxygen, macronutrients, micronutrient and contaminant trace metals in the dissolved and particulate phases, pH/DIC/alkalinity, dissolved and particulate organic carbon, and total suspended solids. We are also interested in identifying the best tracers for deep-sea mining impacts, both by sensors and by more sensitive chemical measurements, as well as experiments outlining the longer-term transformations of mining discharged chemicals in the water column.

    3. Hydrothermal Estuaries: What sets the hydrothermal flux of Fe and Mn to the oceans? National Science Foundation, OCE-1851078 (6/1/19 – 5/31/22). Lead-PI: Chris German (WHOI). Co-PIs: Brandy Toner (Minnesota), Chip Breier (UTRGV), Guangyu Xu (APL-UW).

    Student: Shelby Gunnells

    This project will fill a critical knowledge gap in understanding the impact of hydrothermal venting on ocean chemistry by combining state-of-the-art plume modeling, AUV-based water column surveys, and GEOTRACES-quality marine biogeochemistry. We will conduct our work at the Endeavor Segment of the Juan de Fuca Ridge, which is one of few locations on Earth where one can effectively model the track of a dispersing hydrothermal plume over the critical 1-100 km length scale that determines the ultimate flux of metals such as Fe and Mn into the ocean interior. We will complete GEOTRACES-quality soluble, colloidal, dissolved, and particulate metal analyses, complemented by He isotope, Fe-binding ligand and siderophore, POC, DOC, and dissolved oxygen analyses to determine the biotic and abiotic processes involved in setting these critical ocean fluxes of micronutrient metals.

    4. U.S. GEOTRACES Pacific Meridional Transect (PMT), National Science Foundation, OCE-1737167 (11/2017 – 10/2022). Co-PI Claire Till, Humboldt State University.

    Student: Nate Lanning

    This is a project to measure the dissolved and colloidal micronutrient metal concentrations of a suite of eight metals (Fe, Mn, Zn, Cu, Cd, Ni, Pb, and Sc) across the Northern and Southern Central Pacific Ocean along 152°W as a part of the International GEOTRACES Program (Section GP15). We aim to determine the input and output fluxes of metals in this dynamic ocean basin, as well as how the size partitioning of the dissolved metal phase determines its fate with respect to scavenging and biological uptake. The cruise section goes from Seattle, WA, to Tahiti and took place from September-November 2018.

    5. Iron isotopes in seawater using multi-collector ICP-MS.

    Student: Janelle Steffen

    The Williams Radiogenic Lab at Texas A&M was funded by the National Science Foundation and Texas A&M for the acquisition of a new high-resolution, multi-collector ICP-MS instrument, the ThermoFisher Scientific Neptune Plus. This instrument will be used for the analysis of stable iron isotopes in seawater, which can be used to trace the source of iron to the ocean, as well as track any isotope-fractionating that iron is undergoing in seawater. Samples from three ocean regions/projects are archived in the lab for analysis: (1) soluble and colloidal-filtered seawater from the 4000-km long, East Pacific Rise hydrothermal plume in the South Pacific Ocean, (2) dissolved samples from West Antarctic Peninsula continental shelf, and (3) dissolved and colloidal seawater from the central California Current.

    6. Heavy metal contaminants and lead isotopes in waters and sediments of Galveston Bay, Texas.

    Students: Yerim Kim and previously Mandy Mulcan Lopez (University of Houston)

    This is a project funded by the Galveston Bay Estuary Program (Texas Commission on Envionrmental Quality) in collaboration with Alan Brandon (University of Houston) and by the Texas A&M University T3 Triad program and College of Geosciences High Impact Learning Program in collaboration with Oceanography faculty Franco Marcantonio, Gerardo Gold, Shari Yvon-Lewis, Katie Shamberger, and Kristen Thyng, Civil Engineering faculty Jim Kaihatu and Bella Chu, and Texas A&M Galveston faculty Antonietta Quigg. We are investigating heavy metal and organic pollutant inputs and estuarine acidification in Galveston Bay with seasonal cruises each year. The 2017-2018 cruises captured the effects of Hurricane Harvey on Galveston Bay, while 2019 cruises captured the effects of the Deer Park ITC fire/spill, with additional cruises into the San Jacinto and Trinity Rivers. Graduate and undergraduate students have all participated in these day cruises and sample analyses of the water column, air, sediment, and oyster samples. Fitzsimmons lab students have measured heavy metals in the waters, sediments, and oysters of Galveston Bay and aim to use lead (Pb) isotopes to track sources of heavy metals to different parts of the Galveston Bay estuary.


    Past Projects: 

    1. U.S. Arctic GEOTRACES, National Science Foundation, OCE-1434493 (1/2015 – 12/2019). Co-PI Robert Sherrell, Rutgers University.

    Student: Laramie Jensen (2015-2020, Ph.D.) – Now a postdoc at University of Washington, Cooperative Institute for Climate, Ocean, and Ecosystem Studies.

    This was a project to measure the dissolved and colloidal micronutrient metal concentrations of a suite of eight metals (Fe, Mn, Zn, Cu, Cd, Ni, Pb, and Sc) across the Western Arctic Ocean as a part of the International GEOTRACES Program (Section GN01). We aimed to identify which polar and biological processes, many of which are already undergoing fundamental changes as a result of climate warming, control the inputs and fate of essential micronutrient metals in the Arctic Ocean. This cruise went in and out of Dutch Harbor, Alaska and took place in Fall 2015. The archived data product can be found at BCO-DMO (Dataset 817259), and we have many publications describing our conclusions. 

    2. Physicochemical speciation of dissolved iron, National Science Foundation, OCE 1558722 (9/2014 – 8/2018). Lead-PI Mark Wells, University of Maine.

    Student: Kimber De Salvo Anderson (2016-2018, M.S.) – Now the Gulf Program Coordinator at the Turtle Island Restoration Network.

    This was a project to develop a new method of flow-field flow fractionation coupled to inductively-coupled plasma mass spectrometry in order to measure the size distribution and chemical composition of marine colloidal iron. Colloidal iron (the portion of dissolved iron falling into the size range of 3-200 nm) makes up a large component of the marine dissolved iron inventory, yet its reactivity and biogeochemical fate is oftentimes more like particulate than dissolved iron. Resolving the relative sizes and composition of the different species that compose the colloidal iron pool is an important step toward understanding the chemical transformations that modulate dissolved iron distributions in the open ocean. This project included several short cruises to coastal Maine. The archived data product can be found at BCO-DMO (Project 805258).

    3. Imaging and chemical composition of marine colloidal iron in Galveston Bay.

    Student: Laramie Jensen

    This was a project in collaboration with Brandy Toner at the University of Minnesota to use high resolution imaging techniques to image and measure the fine-scale chemical composition of marine colloidal iron. We explored transmission electronic microscopy techniques as well as synchrotron imaging and speciation techniques such as Scanning Transmission X-ray Microscopy (STXM) at the Advanced Light Source in Berkeley, CA. Samples were collected opportunistically from Galveston Bay, ultrafiltered to collect their colloidal content, and preserved for imaging. This application pushes the spatial resolution of these cutting-edge imaging techniques but will provide much needed information on the associations of metals and organic compounds within the dissolved phase, as it is these associations that control the bioavailability and scavenging fate of marine metals.