About

Jessica Fitzsimmons is a chemical oceanographer at Texas A&M University with a focus on the biogeochemical cycling of trace metals in the ocean. Her research investigates the distribution, physicochemical speciation, and isotope ratios of trace metals such as iron, copper, manganese, zinc, cadmium, and nickel in seawater. These metals are essential nutrients for marine organisms, act as pollutants, and serve as tracers for oceanographic processes. Her work emphasizes understanding how trace metals influence phytoplankton growth, which is at the base of the marine food web and plays a significant role in the global carbon cycle and climate regulation. Fitzsimmons's group conducts sea-going research, collecting samples at sea and analyzing them using inductively coupled plasma mass spectrometry (ICP-MS) in her laboratory, and collaborates closely with other labs measuring biological, geological, and physical parameters to interpret the data within the context of the global ocean system. Her educational background includes a Ph.D. in Chemical Oceanography from MIT/WHOI Joint Program and a B.A. in Chemistry and Biology from Boston University. She has received numerous awards and honors, including the Chancellor's EDGES Fellowship, Kavli Fellow, and the International Association of the Physical Sciences of the Oceans Early Career Award, among others.

Research topics

• Geology
• Oceanography
• Chemistry
• Environmental science
• Geochemistry
• Computer Science
• Environmental chemistry
• Geomorphology
• Human–computer interaction
• Earth science
• Chromatography
• Materials science
• Organic chemistry
• Data science

Selected publications

• Iron supply to the Amundsen Sea, Antarctica is dominated by circumpolar deepwater and continental subglacial sources

  Communications Earth & Environment · 2026-02-26

  articleOpen access

  Glacial melting in West Antarctica has intensified with the increased intrusion of warm ocean water beneath ice shelves, but the processes controlling the export of meltwater-associated micronutrient iron (Fe) to Southern Ocean surface waters remain unclear. Here, we report Fe concentrations and dissolved Fe (dFe) isotope ratios in the inflowing deepwater layer that drives melting of the Dotson Ice Shelf and in the meltwater-enriched outflow to determine meltwater-derived dFe. Isotopic mass balance points to an anoxic Fe-reducing region of the upstream subglacial hydrologic system as the dominant source of meltwater dFe, rather than ice shelf melt itself. Remarkably, total meltwater contributes only ~10% of outflowing dFe, with the majority contributed by inflowing deep water (62%), augmented by inputs from shelf sediments (28%). Outflowing suspended particulate Fe exceeds inflow by 46%, at 100 times the dFe concentration, with 25% in reactive phases. Predictive models of future ecosystem effects should consider that the primary role of ice shelf melting is to provide buoyancy that transports Fe from deep sources to the Fe-limited surface ocean, stimulating phytoplankton growth. Meltwater generated within the Dotson Ice Shelf cavity supplies little dissolved iron. Most meltwater-derived iron found in water flowing out of the cavity comes from subglacial discharge, based on iron concentrations and dissolved iron isotope ratios.

  PublisherOA PDFDOI

• Correction to “Ecological Impacts of Deep-Sea Mining Waste on Marine Algae and Copepod <i>Tigriopus californicus</i> ”

  Environmental Science & Technology · 2026-02-11

  articleOpen access
  PublisherDOI

• Iron supply to the Amundsen Sea, Antarctica is dominated by circumpolar deepwater and continental subglacial sources

  Zenodo (CERN European Organization for Nuclear Research) · 2026-01-14 · 1 citations

  datasetOpen access

  The geochemical data provided here is used in the manuscript entitled "Iron supply to the Amundsen Sea, Antarctica is dominated by circumpolar deepwater and continental subglacial sources," which is accepted for publication in the Nature portfolio journal Communications Earth and Environment. This dataset has been archived for open access.

  PublisherDOI

• Iron supply to the Amundsen Sea, Antarctica is dominated by circumpolar deepwater and continental subglacial sources

  Open MIND · 2026-01-14

  dataset

  The geochemical data provided here is used in the manuscript entitled "Iron supply to the Amundsen Sea, Antarctica is dominated by circumpolar deepwater and continental subglacial sources," which is accepted for publication in the Nature portfolio journal Communications Earth and Environment. This dataset has been archived for open access.

  DOI

• Multi‐Elemental Tracers in the Amerasian Basin Reveal Interlinked Biogeochemical and Physical Processes in the Arctic Ocean Upper Halocline

  Global Biogeochemical Cycles · 2025-04-01 · 2 citations

  articleOpen access

  Abstract The physical and biogeochemical properties of the western Arctic Ocean are rapidly changing, resulting in cascading shifts to the local ecosystems. The nutrient‐rich Pacific water inflow to the Arctic through the Bering Strait is modified on the Chukchi and East Siberian shelves by brine rejection during sea ice formation, resulting in a strong halocline (called the Upper Halocline Layer (UHL)) that separates the cold and relatively fresh surface layer from the warmer and more saline (and nutrient‐poor) Atlantic‐derived water below. Biogeochemical signals entrained into the UHL result from Pacific Waters modified by sediment and river influence on the shelf. In this synthesis, we bring together data from the 2015 Arctic U.S. GEOTRACES program to implement a multi‐tracer (dissolved and particulate trace elements, radioactive and stable isotopes, macronutrients, and dissolved gas/atmospheric tracers) approach to assess the relative influence of shelf sediments, rivers, and Pacific seawater contribution to the Amerasian Arctic halocline. For each element, we characterized their behavior as mixing dominated (e.g., dCu, dGa), shelf‐influenced (e.g., dFe, dZn), or a combination of both (e.g., dBa, dNi). Leveraging this framework, we assessed sources and sinks contributing to elemental distributions: shelf sediments (e.g., dFe, dZn, dCd, dHg), riverine sources, (e.g., dCu, dBa, dissolved organic carbon), and scavenging by particles originating on the shelf (e.g., dFe, dMn, dV, etc.). Additionally, synthesized results from isotopic and atmospheric tracers yielded tracer age estimates for the Upper Halocline ranging between 1 and 2 decades on a spatial gradient consistent with cyclonic circulation.

  PublisherDOI

• Antarctic glaciers export carbon-stabilised iron(II)-rich particles to the surface Southern Ocean

  Nature Communications · 2025-05-30 · 9 citations

  articleOpen access

  Iron is an essential micronutrient for phytoplankton and plays an integral role in the marine carbon cycle. The supply and bioavailability of iron are therefore important modulators of climate over glacial-interglacial cycles. Inputs of iron from the Antarctic continental shelf alleviate iron limitation in the Southern Ocean, driving hotspots of productivity. Glacial meltwater fluxes can deliver high volumes of particulate iron. Here, we show that glacier meltwater provides particles rich in iron(II) to the Antarctic shelf surface ocean. Particulate iron(II) is understood to be more bioavailable to phytoplankton, but less stable in oxic seawater, than iron(III). Using x-ray microscopy, we demonstrate co-occurrence of iron and organic carbon-rich phases, suggesting that organic carbon retards the oxidation of potentially-bioavailable iron(II) in oxic seawater. Accelerating meltwater fluxes may provide an increasingly important source of bioavailable iron(II)-rich particles to the Antarctic surface ocean, with implications for the Southern Ocean carbon pump and ecosystem productivity.

  PublisherOA PDFDOI

• Particulate Cadmium Accumulation in the Mesopelagic Ocean

  Global Biogeochemical Cycles · 2025-01-01 · 6 citations

  articleOpen access

  ) suggest an unexplained loss of dCd to the particulate phase in tropical oxyclines. Here, we compile existing observations of particulate Cd and phosphorus (P), and present new data from the US GEOTRACES GP15 Pacific Meridional Transect to examine this phenomenon from a particulate Cd perspective. We use a simple algorithm to reproduce station depth profiles of particulate Cd and P via regeneration and possible subsurface accumulation. Our examination of regeneration reveals decoupling of particulate Cd and P driven by variable partitioning between two particulate pools with differing labilities. Further, we identify evidence for subsurface particulate Cd accumulation at 31 stations. Subsurface particulate Cd accumulation occurs most consistently in the mesopelagic tropical Pacific but can be found in all examined ocean basins. This accumulation is not well-correlated with dissolved oxygen or particulate sulfide concentration. Instead, we observe that particulate Cd accumulation occurs in regions where the concentration of dCd is relatively high compared to dissolved zinc (dZn) and speculate that it is the result of enhanced dCd biological uptake in response to the subsurface micronutrient balance.

  PublisherOA PDFDOI

• Anthropogenic iron alters the spring phytoplankton bloom in the North Pacific transition zone

  Proceedings of the National Academy of Sciences · 2025-06-02 · 5 citations

  articleOpen access

  Industrial activities have increased the supply of iron to the ocean, but the magnitude of anthropogenic input and its ecological consequences are not well-constrained by observations. Across four expeditions to the North Pacific transition zone, we document a repeated supply of isotopically light iron from an atmospheric source in spring, reflecting an estimated 39 ± 9 % anthropogenic contribution to the surface ocean iron budget. Expression of iron-stress genes in metatranscriptomes, and evidence for colimitation of ecosystem productivity by iron and nitrogen, indicates that enhanced iron supply should spur spring phytoplankton blooms, accelerating the seasonal drawdown of nitrate delivered by winter mixing. This effect is consistent with regional trends in satellite ocean color, which show a shorter, more intense spring bloom period, followed by an earlier arrival of oligotrophic conditions in summer. Continued iron emissions may contribute to poleward shifts in transitional marine ecosystems, compounding the anticipated impacts from ocean warming and stratification.

  PublisherOA PDFDOI

• Does surface seawater actively trace the Pb isotope ratios of aerosol Pb? A case study of the low-dust South Pacific and Southern Oceans

  2025-01-01

  article
  PublisherDOI

• Enigmatic H2- and CH4-rich hydrothermal plumes at the ultramafic-hosted Lucky B site, 81°N on Lena Trough, Arctic Ocean

  Scientific Reports · 2025-10-14

  articleOpen access

  Abstract Tectonic uplift of mantle rocks along slow- and ultraslow-spreading mid-ocean ridges facilitates diverse styles of hydrothermal circulation. Here, we report on Lucky B, an ultramafic-hosted hydrothermal field on the ultraslow-spreading Lena Trough at 81°N in the ice-covered Arctic Ocean. At the seafloor we observed diffuse, metal-poor fluid discharge with abundant vent fauna alongside sites of massive sulfide deposits and hydrothermal chimneys, extending laterally over at least 1.9 km. The overlying water column exhibited two geochemically distinct plumes, the stronger of which showed strong redox and particle anomalies. We hence identify Lucky B as ‘black smoker’-type system featuring distinct styles of venting from several major fluid sources. The strongest plume also contained high concentrations of dissolved hydrogen (H 2 ) and methane (CH 4 ), distinguishing Lucky B from other ultramafic-hosted systems that primarily emit serpentinization-derived H 2 . Low H 2 /CH 4 ratios and high CH 4 relative to dissolved Mn suggest an involvement of sediment in the subseafloor fluid–rock reactions. Our analysis of the plume microbiology revealed abundant chemoautotrophs that use primarily hydrothermal H 2 and sulfide as energy sources. Collectively, these findings reveal multifaceted hydrothermal venting at Lucky B, driven by geological and biogeochemical processes in the subseafloor and extending into the Arctic Ocean water column.

  PublisherOA PDFDOI

Recent grants

• GEOTRACES Arctic section: Dissolved micronutrient trace metal distributions and size partitioning

  NSF · $446k · 2016–2019

• GEOTRACES Arctic section: Dissolved micronutrient trace metal distributions and size partitioning

  NSF · $497k · 2015–2017

• Collaborative Research: U.S. GEOTRACES PMT: Dissolved trace metal distributions and size partitioning

  NSF · $464k · 2017–2022

Frequent coauthors

• Tim M. Conway

  College of Marin

  73 shared

• Seth G. John

  University of Southern California

  70 shared

• Xiaopeng Bian

  University of Southern California

  49 shared

• Nathan T. Lanning

  Texas A&M University

  47 shared

• Matthias Sieber

  Florida State University

  45 shared

• Rene Boiteau

  Oregon State University

  40 shared

• Robert M. Sherrell

  Rutgers, The State University of New Jersey

  38 shared

• Daniel J. Repeta

  31 shared

Labs

• Jessica Fitzsimmons LabPI

Education

• Graduate Student, Earth Atmospheric & Planetary Sciences

  Massachusetts Institute of Technology

  2013

Awards & honors

• Chancellor's EDGES Fellowship, Texas A&M University (2025)
• Kavli Fellow, National Academy of Sciences U.S. Kavli Fronti…
• Distinguished Achievement in Graduate Mentoring Award, Texas…
• Research Impact Award, Texas A&M College of Arts & Sciences…
• International Association of the Physical Sciences of the Oc…