Texas A&M University: Oceanography
3146 TAMU, O&M 408College 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
- Trace metal biogeochemistry
- Metal speciation analyses
- Metal stable isotopes
- Hydrothermal vent chemistry
- Polar Oceanography
- Inductively-Coupled Plasma Mass Spectrometry
- Inorganic Chemical Oceanography
I am a chemical oceanographer interested in the biogeochemical cycling of trace metals in the ocean. Metals such as iron, copper, manganese, zinc, cadmium, and nickel are required nutrients for 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 it is extremely important to understand the sources of metal fluxes into the ocean and which processes modulate the availability of these metals for phytoplankton.
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.
- Ohnemus, DC, Rauschenberg, S, Cutter, GA, Fitzsimmons, JN, Sherrell, RM, & Twining BS. (in press). Elevated trace metal content of prokaryotic communities associated with marine oxygen deficient zones. Limnology & Oceanography.
- Fröllje, H, Pahnke, K, Schnetger, B, Brumsack, H-J, Dulai, H & Fitzsimmons, JN. (2016). Hawaiian imprint on dissolved Nd, and Ra isotopes and rare earth elements in the central North pacific: Local survey and seasonal variability. Geochimica et Cosmochimica Acta, 189: 110-131. doi: 10.1016/j.gca.2016.06.001
- Fitzsimmons, JN, Hayes, CT, Al-Subiai, SN, Zhang, R, Morton, PL, Weisen, RE, Ascani, F, & Boyle, EA. (2015). Daily to decadal variability of size-fractionated iron and iron-binding ligands at the Hawaii Ocean Time-series Station ALOHA. Geochimica et Cosmochimica Acta, 171: 303-324. doi: 10.1016/j.gca.2015.08.012
- Hayes, CT, Fitzsimmons, JN, Boyle, EA, McGee, D, Anderson, RF, Weisend, R, & Morton, PL (2015). Thorium isotopes tracing the iron cycle at the Hawaii Ocean Time-series Station ALOHA. Geochimica et Cosmochimica Acta, 169:1-16. doi:10.1016/j.gca.2015.07.019
- Wilson, ST, Barone, B, Ascani, F, Bidigare, RR, Church, MJ, del Valle, DA, Dyhrman, ST, Ferron, S, Fitzsimmons, JN, Juranek, LW, Kolber, Z, Letelier, RM, Martinez-Garcia, S, Nicholson, D, Richards, KJ, Rii, YM, Rouco, M, Viviani, DA, White, AE, Zehr, JP, and Karl, DM. (2015). Short-term variability in euphotic zone biogeochemistry and primary productivity at Station ALOHA: A case study of summer 2012. Global Biogeochemical Cycles, 29(8): 1145-1164. doi: 10.1002/2015GB005141
- Fitzsimmons, JN, Carrasco, GG, Wu, J, Hatta, M, Measures, CI, Conway, TM, John, SG, & Boyle, EA. (2015). Size partitioning of dissolved iron and iron isotopes along the U.S. GEOTRACES North Atlantic transect. Deep‐Sea Research II, 116: 130‐151. doi:10.1016/j.dsr2.2014.11.014
- Measures, CI, Hatta, M, Fitzsimmons, JN, and Morton, P. (2015). Dissolved Al in the zonal North Atlantic section of the U.S. GEOTRACES 2010/2011 cruises. Deep‐Sea Research II, 116: 176‐186. doi:10.1016/j.dsr2.2014.07.006
- Hatta, M, Measures, CI, Wu, J, Roshan, S, Fitzsimmons, JN, & Morton, P. (2015). Dissolved Fe and Mn concentrations in the North Atlantic during the GEOTRACES 2010/2011 cruises. Deep‐Sea Research II, 116: 117‐129. doi:10.1016/j.dsr2.2014.07.005
- Fitzsimmons, JN, Bundy, RM, Al‐Subiai, SN, Barbeau, KA, & Boyle, EA. (2015). The composition of dissolved iron in the dusty surface ocean: An exploration using size‐fractionated iron‐binding ligands. Marine Chemistry, 173: 125‐135. doi:10.1016/j.marchem.2014.09.002
- Mawji, E, and The GEOTRACES group, including Fitzsimmons, JN. (2015). The GEOTRACES Intermediate Data Product 2014. Marine Chemistry.177: 1-8. doi: 10.1016/j.marchem.2015.04.005
- Fitzsimmons, JN, Boyle, EA, and Jenkins, WJ (2014). Distal transport of dissolved hydrothermal iron in the deep South Pacific Ocean. Proceedings of the National Academy of Sciences, 111: 16654‐16661. doi:10.1073/pnas.1418778111
- Fitzsimmons, JN & Boyle, EA (2014). Assessment and comparison of Anopore and cross flow filtration methods for the determination of dissolved iron size fractionation into soluble and colloidal phases in seawater. Limnology & Oceanography: Methods, 12: 244‐261. doi: 10.4319/lom.2014.12.246
- Fitzsimmons, JN & Boyle, EA (2014). Both soluble and colloidal iron phases control dissolved iron variability in the tropical North Atlantic Ocean. Geochimica et Cosmochimica Acta, 125: 539‐550. doi:10.1016/j.gca.2013.10.032
- Fitzsimmons, JN, Zhang, R, & Boyle, EA (2013). Dissolved iron in the tropical North Atlantic Ocean. Marine Chemistry, 154: 87‐99. doi:10.1016/j.marchem.2013.05.009
- Boiteau, R, Fitzsimmons, JN, Repeta, D, & Boyle, EA (2013). A method for the characterization of iron ligands in seawater and marine cyanobacteria cultures by HPLC‐ICPMS. Analytical Chemistry, 85: 4357‐4362. doi:10.1021/ac3034568
- Fitzsimmons, JN & Boyle, EA (2012). An intercalibration between the GEOTRACES GO‐FLO and the MITESS/Vanes sampling systems for dissolved iron concentration analyses (and a closer look at adsorption effects). Limnology & Oceanography: Methods, 10: 437‐450. doi: 10.4319/lom.2012.10.437
- Lee, J‐M, Boyle, EA, Echegoyen‐Sanz, Y, Fitzsimmons, JN, Zhang, R, Kayser, RA (2011). Analysis of trace metals (Cu, Cd, Pb, and Fe) in seawater using single batch nitrilotriacetate resin extraction and isotope dilution inductively coupled plasma mass spectrometry. Analytica Chimica Acta, 686: 93‐101. doi:10.1016/j.aca.2010.11.052
The Fitzsimmons lab is always interested in bringing on motivated undergraduate, graduate, and professional personnel. Please contact firstname.lastname@example.org for more information!
1. U.S. Arctic GEOTRACES, National Science Foundation, OCE, 1434493 (1/2015 – 12/2017)
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. Physicochemical speciation of dissolved iron, National Science Foundation, OCE 1558722 (9/2014 – 8/2017).
This is a project co-funded with lead-PI Dr. Mark Wells at the University of Maine to use the relatively new method of flow-field flow fractionation to investigate the size distribution and chemical composition of marine colloidal iron. Colloidal iron (the portion of dissolved iron falling into the size range of 10 kDa - 0.2 um) 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.
3. California Current iron limitation mosaic. The central California Current system is known to contain steep gradients in iron concentrations over relatively short spatial scales. In upwelling regions along wide continental shelves, iron is supplied by shelf sediments to support large phytoplankton blooms, while along narrow shelves upwelling supplies sufficient macronutrients but insufficient iron, such that phytoplankton are limited by iron delivery. We will use iron isotopes measured in seawater samples collected on a summer 2014 cruise to quantify the various iron sources to the central California Current system as a function of distance from shore, shelf width, location within eddies, and water mass. We will also evaluate the physicochemical speciation of these dissolved iron species to evaluate whether soluble or colloidal iron compounds are more bioavailable to local phytoplankton and how this speciation influences the transport and scavenging fate of dissolved iron.