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Dr. Jessica Fitzsimmons
Jessica Fitzsimmons
(979) 845-5137
(979) 845-6331
Eller O&M 403A

Texas A&M University

Department of Oceanography

3146 TAMU, O&M 403

College Station, TX 77843-3146



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


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


OCNG 251 – Oceanography

OCNG 641 – Inorganic Aquatic Geochemistry

Jessica Fitzsimmons

Assistant Professor
Chemical Oceanography: Trace Metal and Nutrient Cycling

Research Interests

The Fitzsimmons Lab is always recruiting curious and motivated students at the undergraduate, graduate, and postdoctoral levels. Please contact 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


I am 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 control 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 throughout the geologic past. Thus, if trace metal cycling modulates phytoplankton dynamics, then trace metals also play a role in global carbon cycling and thus global climate, making it important to study in the face of modern climate change.

My 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, geologic, and physical parameters of our study regions, which frames our interpretation in the context of the global ocean system.

Selected Publications

  • 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
  • Hein, JR, Konstantinova, N, Mikesell, M, Mizell, K, Fitzsimmons, JN, Lam, PJ, Jensen*, LJ, Xiang, Y, Gartman, A, Cherkashov, G, Hutchinson, DR. (2017). Arctic deep-water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean. Geochemistry, Geophysics, Geosystems, 18. doi: 1002/2017GC007186
  • 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: 1038/ngeo2900
  • Wilson, ST, Aylward, FO, Ribalet, F, Barone, B, Casey, JR, Connell, PE, Eppley, JA, Ferrón, S, Fitzsimmons, JN, Hayes, CT, Romano, AE, Turk-Kubo, KA, Vislova, A, Armbrust, EV, Caron, DA, Church, MJ, Zehr, JP, Karl, DM, DeLong, EF. (2017) Coordinated regulation of growth activity, and transcription in natural populations of the unicellular nitrogen-fixing cyanobacterium Crocosphaera. Nature Microbiology: 2: 17118. doi: 1038/nmicrobiol.2017.118
  • Annett, AL, Fitzsimmons, JN, Séguret, M, Lagerström, M, Meredith, MP, Schofield, O, and Sherrell, RM. (in press) Controls on dissolved and particulate iron distributions in surface waters of the Western Antarctic Peninsula shelf. Marine Chemistry. doi: 1016/j.marchem.2017.06.004
  • Ohnemus, DC, Rauschenberg, S, Cutter, GA, Fitzsimmons, JN, Sherrell, RM, Twining, BS (2017). Elevated trace metal content of prokaryotic communities associated with marine oxygen deficient zones. Limnology & Oceanography, 62(1): 3-25. doi: 1002/lno.10363
  • Boiteau, RM, Mende, DR, Hawco, NJ, McIlvin, MR, Fitzsimmons, JN, Saito, MA, Sedwick, PN, Delong, EF, Repeta, DJ (2016). Siderophore-based microbial adaptations to iron scarcity across the eastern Pacific Ocean. Proceedings of the National Academy of Sciences, 113(50): 14237-14242. doi: 1073/pnas.1608594113
  • Fitzsimmons, JN, Conway, TM, Lee, J-M, Kayser, RA, Thyng, KM, John, SG, Boyle, EA. (2016). Dissolved iron and iron isotopes in the Southeastern Pacific Ocean. Global Biogeochemical Cycles. 30. doi: 1002/2015GB005357
See publications prior to 2016 on Google Scholar.

Additional Information

Current Students:

  1. Laramie Jensen (Ph.D. student)
  2. Kimber De Salvo (M.S. student)
  3. Janelle Steffen (Ph.D. student)
  4. Nathan Lanning (Ph.D. student)
  5. Reagan Lucas (TAMU undergraduate)
  6. Hannah Adams (REU undergraduate student from USC)



  1. U.S. GEOTRACES Pacific Meridional Transect (PMT), National Science Foundation, OCE-1737167 (11/2017 – 10/2020).
    Student: Nate Lanning
    This is a project co-funded with the Till Lab at Humboldt State University to measure the dissolved and colloidal micronutrient metal concentrations of a suite of eight metals (Fe, Mn, Zn, Cu, Cd, Ni, Pb, and Sc) in the Central Pacific Ocean. 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 is scheduled for Fall 2018.


  1. U.S. Arctic GEOTRACES, National Science Foundation, OCE-1434493 (1/2015 – 12/2018).
    Student: Laramie Jensen
    This is a project co-funded with the Sherrell lab at Rutgers to measure the dissolved and colloidal micronutrient metal concentrations in the Western Arctic Ocean. We aim 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.

  2. Iron isotopes in seawater using multi-collector ICP-MS.
    Student: Janelle Steffen
    The Williams Radiogenic Lab at Texas A&M has been 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.


  1. Physicochemical speciation of dissolved iron, National Science Foundation, OCE 1558722 (9/2014 – 8/2018).
    Student: Kimber De Salvo
    This is a project co-funded with lead-PI Dr. Mark Wells at the University of Maine to use the 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 includes several short cruises to coastal Maine and two cruises to Station ALOHA near Hawaii. 


  1. Heavy metal contaminants in waters and sediments of Galveston Bay, Texas.
    Students: Lab effort of graduate and undergraduate students
    This is a project funded by the Texas A&M University T3 Triad program and College of Geosciences High Impact Learning funds in collaboration with Oceanography faculty Dr. Gerardo Gold, Dr. Shari Yvon-Lewis, Dr. Katie Shamberger, and Dr. Kristen Thyng, Civil Engineering faculty Dr. Bella Chu, and Texas A&M Galveston faculty Dr. Antonietta Quigg. We are investigating organic and inorganic 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, and cruises are expected to continue through 2018-2019, with additional cruises into the San Jacinto and Trinity Rivers funded by the NSF. Graduate and undergraduate students have all participated in these day cruises and sample analyses of the water column, air, and sediment samples.

  2.  Imaging and chemical composition of marine colloidal iron in Galveston Bay.
    Student: Laramie Jensen and recruiting others interested
    This is a project in collaboration with Dr. 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 are exploring 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 are 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.
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