Skip to main content
Skip to main menu Skip to spotlight region Skip to secondary region Skip to UGA region Skip to Tertiary region Skip to Quaternary region Skip to unit footer


Patricia M. Medeiros

Blurred image of the arch used as background for stylistic purposes.
Aquatic Organic Geochemistry

My expertise relies on the use of specific organic compounds, i.e., molecular biomarkers to investigate sources, transport, transformations, and fate of organic matter in the aquatic and atmospheric environments. Most studies in my lab on the characterization of organic matter in environmental samples were primarily focused on the analysis of sediments and/or the particulate fraction. The utilization of Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) by the aquatic organic geochemistry community opened a new door to the analysis of the most abundant and biologically important fraction of organic matter: the dissolved fraction. The analysis of DOM (dissolved organic matter) using FT-ICR MS is now the main branch of my research and collaborations. Since 2010, thousands of DOM samples were analyzed using FT-ICR MS encompassing various projects that my lab either led or collaborated with other groups in USA and Europe (see recent publications and Research below).


Medeiros Lab People:

  • Giovanna Utsumi (Ph.D. student, 2019-ongoing)
  • Aiden Schuster (M.S. student, 2023-ongoing)

Medeiros Lab Alumni:

      Postdocs/Research Associate

  • Michael Seidel (Postdoc, 2012-2015) - Now: Senior Scientist at the ICBM, University of Oldenburg, Germany
  • Ding He (Postdoc, 2014-2016) - Now: Assistant Professor at the Hong Kong University of Science and Technology, Hong Kong
  • Sylvia Schaefer (Research Associate, 2017-2019)

      Graduate students

  • Lydia ('Meg') Babcock-Adams (M.S. student, 2013-2016) - Now: Postdoctoral Associate at the MagLab (ICR), Florida State University
  • Maria Letourneau (Ph.D. student, 2015-2020) - Now: Researcher at the EPA (Water Quality), Washington, D.C.
  • Kellie White (NT-M.S. student, 2021-2022) - Now: Propagation and Restoration Biologist at the Cumberland River Aquatic Center, Tennessee
  • Rachel Martineac (Ph.D. student, 2018-2023) - Now: Data Scientist at SATCOM Direct, Melbourne, Florida

      Undergraduate students

  • Danielle Arnold (IDS undergraduate student, 2012-2013)
  • V. Ruth Pannill (IDS undergraduate student, 2016-2018) - Now: M.S. student at the University of Arizona
  • Erin Malsbury (Undergraduate student (Ecology), 2018-2019)


  • Ph.D. 2006, Oregon State University (Environmental Sciences/Chemical Oceanography)
Research Interests:

Organic geochemistry and biogeochemistry:

1. Sources, transport, alterations and fate of organic compounds in aquatic and atmospheric environments;

2. Molecular characterization of riverine/estuarine/marine dissolved organic matter (DOM); 

3. Microbial- and photochemical-derived changes in DOM composition.


See complete list of publications here.

Martineac RP, Castelao RM, Medeiros PM. 2024. Seasonal and interannual variability in the distribution and removal of terrigenous dissolved organic carbon in the Amazon River plume. Global Biogeochemical Cycles. 38, e2023GB007995. Google Scholar

Lønborg C, Carreira C, Abril G, Agusti S, Amaral V, (…), Medeiros PM, and co-authors. 2024. A global database of dissolved organic matter (DOM) measurements in coastal waters (CoastDOM v1). Earth Systems Science Data. 16:1107-1119. Google Scholar

Reimer JJ, Medeiros PM, Hussain N, Gonski SF, Xu Y-Y, Huang T-H, Cai W-J. 2024. Carbonate chemistry and the potential for acidification in Georgia coastal marshes and the South Atlantic Bight, USA. Estuaries and Coasts. 47:76-90. Google Scholar

Castelao RM, Oliver H., Medeiros PM. 2023. A Lagrangian view of transport pathways in the Labrador Sea. Remote Sensing. 15, 5545. Google Scholar

Castelao RM, Medeiros PM. 2022. Coastal summer freshening and meltwater input off west Greenland from satellite observations. Remote Sensing. 14, 6069. Google Scholar

Medeiros PM. 2022. The effects of hurricanes and storms on the composition of dissolved organic matter in a southeastern U.S. estuary. Frontiers in Marine Science. 9:855720. Google Scholar

Martineac RP, Vorobev AV, Moran MA, Medeiros PM. 2021. Assessing the contribution of seasonality, tides, and microbial processing to dissolved organic matter composition variability in a Southeastern U.S. estuary. Frontiers in Marine Science. 8:781580. Google Scholar

Letourneau ML, Schaefer SC, Chen H, McKenna AM, Alber M, Medeiros PM. 2021. Spatio-temporal changes in dissolved organic matter composition along the salinity gradient of a marsh-influenced estuarine complex. Limnology and Oceanography. 66:3040-3054. Google Scholar 

Castelao RM, Dinniman MS, Amos CM, Klinck JM, Medeiros PM. 2021. Eddy-driven transport of particulate organic carbon off the West Antarctic Peninsula. Journal of Geophysical Research: Oceans. 126, e2020JC016791. Google Scholar

Phillips AA, Speth DR, Miller LG, Wand XT, Wu F, Medeiros PM, Monteverde DR, Osburn MR, Berelson WM, Betts HL, Wijker RS, Mullin SW, Johnson HA, Orphan VJ, Fischer WW, Sessions AL. 2021. Microbial succession and dynamics in meromictic Mono Lake, California. Geobiology. 19:376-393. Google Scholar

Gifford SM, Zhao A, Stemple B, DeLong K, Medeiros PM, Seim H, Marchetti A. 2020. Microbial niche diversification in the Galápagos Archipelago and its response to El Niño. Frontiers in Microbiology. 11:575194. Google Scholar

Letourneau ML, Hopkinson BM, Fitt WK, Medeiros PM. 2020. Molecular composition and biodegradation of loggerhead sponge Spheciospongia vesparium exhalent dissolved organic matter. Marine Environmental Research. 162:105130. Google Scholar 

Amos CM, Castelao, RM, Medeiros, PM. 2019. Offshore transport of particulate organic carbon in the California Current System by mesoscale eddies. Nature Communications. 10:4940 (1-8). Google Scholar

Letourneau ML, Medeiros PM. 2019. Dissolved organic matter composition in a marsh-dominated estuary: Response to seasonal forcing and to the passage of a hurricane. Journal of Geophysical Research: Biogeosciences. 124:1545-1559. Google Scholar Eos - Editor Research Spotlight

Castelao RM, Luo H, Oliver H, Rennermalm A, Tedesco M, Bracco A, Yager PL, Mote T, Medeiros PM. 2019. Controls on the transport of meltwater from the southern Greenland ice sheet in the Labrador Sea. Journal of Geophysical Research: Oceans. 124:3551-3560. Google Scholar

Simoneit BRT, Oros DR, Leif RN, Medeiros PM. 2019. Weathering and biodegradation of hydrothermal petroleum in the North Rift of Guaymas Basin, Gulf of California. Revista Mexicana de Ciencias Geológicas. 36:159-169. Google Scholar

Roebuck JA, Medeiros PM, Letourneau ML, Jaffe R. 2018. Hydrological controls on the seasonal variability of dissolved and particulate black carbon in the Altamaha River, GA. Journal of Geophysical Research: Biogeosciences. 123:3055-3071. Google Scholar

Vorobev A, Sharma S, Yu M, Lee J, Washington BJ, Whitman WB, Ballantyne F, Medeiros PM, Moran MA. 2018. Identifying labile marine DOM through short-term depletion of bacterioplankton transcripts and chemical signals. Environmental Microbiology. 20:3012-3030. Google Scholar

Galeron M-A, Radakovitch O, Charrière B, Vaultier F, Volkman JK, Bianchi TS, Ward ND, Medeiros PM, Sawakuchi HO, Tank S et al..  2018.  Lipoxygenase-induced autoxidative degradation of terrestrial particulate organic matter in estuaries: A widespread process enhanced at high and low latitude. Organic Geochemistry. 115:78-92. Google Scholar 

Medeiros PM.  2018.  Encyclopedia of Geochemistry: Gas Chromatography-Mass Spectrometry (GC-MS). In: Encyclopedia of Earth Sciences Series. W.H. White (ed.). pp. 1-6. Google Scholar (see the new Encyclopedia of Geochemistry here)

Babcock-Adams L, Chanton JP, Joye SB, Medeiros PM.  2017.  Hydrocarbon composition and concentrations in the Gulf of Mexico sediments in the 3 years following the Macondo well blowout. Environmental Pollution. 229:329-338. Google Scholar 

Medeiros PM, Babcock-Adams L, Seidel M, Castelao RM, Di Iorio D, Hollibaugh JT, Dittmar T.  2017.  Export of terrigenous dissolved organic matter in a broad continental shelf. Limnology and Oceanography. 62:1718-1731. Google Scholar 

Doherty M, Yager PL, Moran MAnn, Coles VJ, Fortunato CS, Krusche AV, Medeiros PM, Payet JP, Richey JE, Satinsky BM et al..  2017.  Bacterial biogeography across the Amazon River-ocean continuum. Frontiers in Microbiology. 8:882.  Google Scholar 

Satinsky BM, Smith CB, Sharma S, Landa M, Medeiros PM, Coles VJ, Yager PL, Crump BC, Moran MAnn.  2017.  Expression patterns of elemental cycling genes in the Amazon River Plume. The ISME Journal. 11:1852-1864. Google Scholar 

Medeiros PM, Seidel M, Gifford SM, Ballantyne F, Dittmar T, Whitman WB, Moran MAnn.  2017.  Microbially-mediated transformations of estuarine dissolved organic matter. Frontiers in Marine Science. 4:69. Google Scholar 

John DL, Medeiros PM, Babcock-Adams L, Walker SE.  2017.  Cambrian trilobites as archives for anthropocene biomarkers and other chemical compounds. Anthropocene. 17:99-106. Google Scholar 

Ward ND, Bianchi TS, Medeiros PM, Seidel M, Richey JE, Keil RG, Sawakuchi HO.  2017.  Where carbon goes when water flows: Carbon cycling across the aquatic continuum. Frontiers in Marine Science (Review article). 4:7. Google Scholar 

Cao F, Medeiros PM, Miller WL.  2016.  Optical characterization of dissolved organic matter in the Amazon River plume and the Adjacent Ocean: Examining the relative role of mixing, photochemistry, and microbial alterations. Marine Chemistry. 186:178-188. Google Scholar

Seidel M, Dittmar T, Ward ND, Krusche AV, Richey JE, Yager PL, Medeiros PM.  2016.  Seasonal and spatial variability of dissolved organic matter composition in the lower Amazon River. Biogeochemistry. 131:281-302. Google Scholar 

Craft C., Herbert E., Li F., Smith D., Schubauer-Berigan J., Widney S., Angeline C., Pennings S., Medeiros PM, Byers J. et al..  2016.  Climate change and the fate of coastal wetlands. Wetland Science & Practice. 33(3):70-73. Google Scholar 

Medeiros PM, Seidel M, Niggemann J, Spencer RGM, Hernes PJ, Yager PL, Miller WL, Dittmar T, Hansell DA.  2016.  A novel molecular approach for tracing terrigenous dissolved organic matter into the deep ocean. Global Biogeochemical Cycles. 30:689-699. Google Scholar 

Seidel M, Kleindienst S, Dittmar T, Joye SB, Medeiros PM.  2016.  Biodegradation of crude oil and dispersants in deep seawater from the Gulf of Mexico: Insights from ultra-high resolution mass spectrometry. Deep Sea Research Part II: Topical Studies in Oceanography. 129:108-118. Google Scholar 

Kleindienst S, Seidel M, Ziervogel K, Grim S, Loftis K, Harrison S, Malkin SY, Perkins MJ, Field J, Sogin ML et al..  2016.  Reply to Prince et al.: Ability of chemical dispersants to reduce oil spill impacts remains unclear. Proceedings of the National Academy of Sciences. 113(11):E1422-E1423. Google Scholar

Loick-Wilde N, Weber SC, Conroy BJ, Capone DG, Coles VJ, Medeiros PM, Steinberg DK, Montoya JP.  2016.  Nitrogen sources and net growth efficiency of zooplankton in three Amazon River plume food webs. Limnology and Oceanography. 61:460-481. Google Scholar 

Moran MAnn, Kujawinski EB, Stubbins A, Fatland R, Aluwihare LI, Buchan A, Crump BC, Dorrestein PC, Dyhrman ST, Hess NJ et al..  2016.  Deciphering ocean carbon in a changing world. Proceedings of the National Academy of Sciences. 113(12):3143-3151. Google Scholar 

Rushdi AI, Oros DR, Al-Mutlaq KF, He D, Medeiros PM, Simoneit BRT.  2016.  Lipid, sterol and saccharide sources and dynamics in surface soils during an annual cycle in a temperate climate region. Applied Geochemistry. 66:1-13. Google Scholar 

Kleindienst S, Seidel M, Ziervogel K, Grim S, Loftis K, Harrison S, Malkin SY, Perkins MJ, Field J, Sogin ML et al..  2015.  Chemical dispersants can suppress the activity of natural oil-degrading microorganisms. Proceedings of the National Academy of Sciences. 112:14900-14905. Google Scholar 

Medeiros PM, Seidel M, Dittmar T, Whitman WB, Moran MA.  2015.  Drought-induced variability in dissolved organic matter composition in a marsh-dominated estuary. Geophysical Research Letters. 42:6446-6453. Google Scholar 

Seidel M, Yager PL, Ward ND, Carpenter EJ, Gomes HR, Krusche AV, Richey JE, Dittmar T, Medeiros PM.  2015.  Molecular-level changes of dissolved organic matter along the Amazon River-to-ocean continuum. Marine Chemistry. 177:218-231. Google Scholar 

Medeiros PM, Seidel M, Ward ND, Carpenter EJ, Gomes HR, Niggemann J, Krusche AV, Richey JE, Yager PL, Dittmar T.  2015.  Fate of the Amazon River dissolved organic matter in the tropical Atlantic Ocean. Global Biogeochemical Cycles. 29:677-690. Google Scholar 

Medeiros PM, Seidel M, Powers LC, Dittmar T, Hansell DA, Miller WL.  2015.  Dissolved organic matter composition and photochemical transformations in the northern North Pacific Ocean. Geophysical Research Letters. 42:863-870. Google Scholar 

Simoneit BRT, Oros DR, Medeiros PM.  2014.  Organic matter provenance and paleoenvironment in the Cretaceous on the Manihiki Plateau, South Pacific. Palaeogeography, Palaeoclimatology, Palaeoecology. 409:48-56. Google Scholar 

Landa M., Cottrell M.T, Kirchman D.L, Kaiser K., Medeiros PM, Tremblay L., Batailler N., Caparros J., Catala P., Escoubeyrou K. et al..  2014.  Phylogenetic and structural response of heterotrophic bacteria to dissolved organic matter of different chemical composition in a continuous culture study. Environmental Microbiology. 16(6):1668-1681. Google Scholar 

Satinsky B.M, Crump B.C, Smith C.B, Sharma S., Zielinski B.L, Doherty M., Meng J., Sun S., Medeiros PM, Paul J.H et al..  2014.  Microspatial gene expression patterns in the Amazon River Plume. Proceedings of the National Academy of Sciences. 111(30):11085–11090. Google Scholar 

Ward ND, Keil RG, Medeiros PM, Brito DC, Cunha AC, Dittmar T, Yager PL, Krusche AV, Richey JE.  2013.  Degradation of terrestrially derived macromolecules in the Amazon River. Nature Geoscience. 6(7):530-533. Google Scholar 

Sikes EL, Medeiros PM, Augustinus P, Wilmshurst JM, Freeman KR.  2013.  Seasonal variations in aridity and temperature characterize changing climate during the last deglaciation in New Zealand. Quaternary Science Reviews. 74:245-256. Google Scholar 

Medeiros PM, Sikes EL, Thomas B, Freeman KH.  2012.  Flow discharge influences on input and transport of particulate and sedimentary organic carbon along a small temperate river. Geochimica et Cosmochimica Acta. 77:317-334. Google Scholar 

Articles Featuring Patricia M. Medeiros

Great new work by marine scientists Caitlin Amos, Renato Castelao and Patricia Medeiros published in Nature Communications:

Dissolved organic matter supports aquatic food webs and holds as much carbon as the atmosphere. A new study tracks which sources and processes play the biggest role in coastal systems.

SOURCE: Journal of Geophysical Research: Biogeosciences

Earlier this year, Patricia Medeiros and Renato Castelao were funded by NSF to investigate carbon export in high latitude…

Mary Ann Moran, Patricia Medeiros and Aron Stubbins have an article appearing today in PNAS, the Proceedings of the National Academy of Sciences, addressing both the complexities and innovations in the field of dissolved organic material in…

Support us

We appreciate your financial support. Your gift is important to us and helps support critical opportunities for students and faculty alike, including lectures, travel support, and any number of educational events that augment the classroom experience. Click here to learn more about giving.

Every dollar given has a direct impact upon our students and faculty.