Breadcrumb

Office: SEEC S256
Bio
Organic and stable isotope biogeochemistry, geobiology, biomarker research, paleoceanography, paleoclimate, extreme climates, mass extinction events
I joined CU in August 2014 as an Assistant Professor in Geological Sciences and Fellow at INSTAAR. I came to CU after having worked as a postdoctoral associate and research scientist in the Geobiology and Astrobiology Group of Prof. Roger Summons in the Department of Earth, Atmospheric and Planetary Sciences at MIT. Originally from Chile, I began my career as a marine biologist (BSc) and chemical oceanographer (MSc) at the University of Concepción, Chile under the supervision of Prof. Silvio Pantoja (Marine Organic Geochemistry Group), where the field of organic biogeochemistry fascinated me. After feeling the desire to explore the world and expand my expertise, I moved to Germany and obtained a PhD in Marine Geosciences from the University of Bremen under the supervision of Prof. Kai-Uwe Hinrichs (Organic Geochemistry Group).
Education
- PhD: Marine Geosciences, University of Bremen, Germany, 2008
- MSc: Oceanography, University of Concepción, Chile, 2005
- BSc: Marine Biology and Oceanography, University of Concepción, Chile, 2001
Awards
- School of Science Infinitive Kilometer Award, MIT, USA, 2012
- MARUM Research Prize – Best PhD thesis in Marine Geosciences, University of Bremen, Germany, 2010
- Best undergraduate thesis in Marine Biology, University of Concepción, Chile, 2000
- Best student presentation in Biological Oceanography, Chilean Society of Marine Sciences, 1999
Research
Organic and stable isotope biogeochemistry, geobiology, biomarker research, paleoceanography, paleoclimate, extreme climates, mass extinction events
My research group studies the interplay between microorganisms, biogeochemical processes, and climate in contemporary settings (e.g., continental margins, marine oxygen minimum zones, extreme environments), and paleo-ecosystems across major climatic/biotic transitions in Earth history (e.g., mass extinction events, greenhouse climates, glacial-interglacial transitions). We approach these systems with a focus on the structures, distributions, and stable isotope composition of cell membrane lipids (biomarkers) that can be identified in water bodies, sediments, soils, and their fossilized remains preserved in the rock record.
Extreme climates over the Phanerozoic
Periods of extreme climates in the geological record are associated with changes in ocean geochemistry and varying degrees of extinction, and can serve as partial analogues to study ecosystem resilience to projected scenarios of ocean deoxygenation and acidification. However, our current understanding of ecosystem’s resilience derives almost exclusively from the body fossil record, thus disregarding important microbial biota lacking hard, fossilizable skeletons, which exert strong control on ocean geochemistry and climate.
My current efforts aim to unravel the role of photoautotrophic eukaryotes and prokaryotes, and chemosynthetic prokaryotes in sustaining carbon fixation across periods of extreme climate change and extinction, as well as to unravel the environmental responses (e.g., water column stratification, oxygenation, nutrient budgets) to CO2 forcing. I currently study five major climatic events associated with varying degrees of extinction during the Mesozoic and Cenozoic: (a) end–Triassic mass extinction; (b) end-Cretaceous mass extinction; (c) early Jurassic OAE; (d) mid-late Cretaceous OAEs; (e) Paleocene-Eocene Thermal Maximum (PETM).
Biogeochemistry of oxygen minimum zones: Past, present, and future
Marine oxygen minimum zones (OMZs) are key areas of the world’s ocean for the recycling of carbon, nutrients and the release of greenhouse gases through microbial processes, therefore influencing the global climate system. OMZs have expanded over the last five decades, and this expansion is expected to continue, in parallel with ocean acidification, in response to current and projected trends of climate change. Therefore, reliable proxies for oxygenation and microbial processes in the past are required to constrain the response of OMZs to future warming scenarios.
My current research efforts aim to illuminate microbially–driven processes in modern oxygen–depleted environments through the tandem analysis of lipid biomarkers and gene-based techniques, as well as the validation of biomarkers as proxies for paleoxygenation and ocean biogeochemistry in sedimentary records. I presently study the provenance and diversity of microbial biomarkers across five distinctive oxygen-depleted marine environments. Results from this study are expected to improve our understanding of biomarkers for microbial metabolism involved in nitrogen and sulfur cycling under different degrees of anoxia/euxinia. Also, I currently study the biogeochemical evolution of the Chilean OMZ over past warm climatic transitions (i.e., Marine Isotope Stages 5 and 11, mid-Holocene warm period). A particular interest is to elucidate the relative role of different denitrifying processes (denitrification vs. anaerobic ammonium oxidation) on controlling nutrient budgets and climate variability. These results should greatly facilitate our interpretation of present and past responses of OMZs to natural and anthropogenic forcing, thus assisting our understanding of potential future scenarios.
Carbon cycling along continental margins and paleoclimatology
Continental margins are important components of the global carbon cycle as they support high levels of primary productivity and increased carbon burial rates. I am interested in the cycling of marine and terrestrial organic mater along continental margins subject to increasingly human pressure. My work also focuses on the validation of organic geochemical proxies for paleoclimate reconstructions. Current areas of study include the fjord system of Patagonia and the upwelling area of central and northern Chile.
Publications
Recent publications
Delayed postglacial colonization of Betula in Iceland and the circum North Atlantic
Type: Journal Article
Delayed postglacial colonization of Betula in Iceland and the circum North Atlantic
Type: Journal Article
Development and Application of the Branched and Isoprenoid GDGT Machine Learning Classification Algorithm (BIGMaC) for Paleoenvironmental Reconstruction
Martinez-Sosa P; Tierney JE; Perez-Angel LC; Stefanescu IC; Guo J; Kirkels F; Sepulveda J; Peterse F; Shuman BN; Reyes A...
- Martinez-Sosa P
- Tierney JE
- Perez-Angel LC
- Stefanescu IC
- Guo J
- Kirkels F
- Sepulveda J
- Peterse F
- Shuman BN
- Reyes AV
Publication Date: 2023-07-01
Type: Journal Article
Delayed postglacial colonization ofBetulain Iceland and the circum North Atlantic
Harning DJ; Sacco S; Anamthawat-Jónsson K; Ardenghi N; Thordarson T; Raberg JH; Sepúlveda J; Geirsdóttir Á; Shapiro ...
- Harning DJ
- Sacco S
- Anamthawat-Jónsson K
- Ardenghi N
- Thordarson T
- Raberg JH
- Sepúlveda J
- Geirsdóttir Á
- Shapiro B
- Miller GH
Type: Journal Article
Development and application of the Branched and Isoprenoid GDGT Machine learning Classification algorithm (BIGMaC) for paleoenvironmental reconstruction
Martínez-Sosa P; Tierney J; Perez-Angel LC; Stefanescu IC; Guo J; Kirkels FMSA; Sepúlveda J; Peterse F; Shuman BN; Rey...
- Martínez-Sosa P
- Tierney J
- Perez-Angel LC
- Stefanescu IC
- Guo J
- Kirkels FMSA
- Sepúlveda J
- Peterse F
- Shuman BN
- Reyes A
Type: Journal Article
Mixed Signals From the Stable Isotope Composition of Precipitation and Plant Waxes in the Northern Tropical Andes
Publication Date: 2022-12-01
Type: Journal Article
Intact Polar brGDGTs in Arctic Lake Catchments: Implications for Lipid Sources and Paleoclimate Applications
Publication Date: 2022-10-01
Type: Journal Article
Bacteriohopanepolyols across the Black Sea redoxcline trace diverse bacterial metabolisms
Publication Date: 2022-08-19
Type: Journal Article
Aquatic and Terrestrial Plant Contributions to Sedimentary Plant Waxes in a Modern Arctic Lake Setting
Publication Date: 2022-08-01
Type: Journal Article
Phytoplankton response to a warming ocean
Publication Date: 2022-06-24
Type: Journal Article
Last interglacial lake sediments preserved beneath Laurentide and Greenland Ice sheets provide insights into Arctic climate amplification and constrain 130 ka of ice-sheet history
MILLER GIFFORDH; WOLFE ALEXANDERP; AXFORD YARROW; BRINER JASONP; BUELTMANN HELGA; CRUMP SARAH; FRANCIS DONNA; FRECHETTE ...
- MILLER GIFFORDH
- WOLFE ALEXANDERP
- AXFORD YARROW
- BRINER JASONP
- BUELTMANN HELGA
- CRUMP SARAH
- FRANCIS DONNA
- FRECHETTE BIANCA
- GORBEY DEVON
- KELLY MEREDITH
Publication Date: 2022-06-09
Type: Journal Article
Near-universal trends in brGDGT lipid distributions in nature
Publication Date: 2022-05-20
Type: Journal Article
Bacterial and eukaryotic intact polar lipids point to in situ production as a key source of labile organic matter in hadal surface sediment of the Atacama Trench
Publication Date: 2022-03-08
Type: Journal Article
Intact Polar Lipids in Surface Sediments of The Atacama Trench Point to In Situ Dominant Sources of Labile Organic Matter in the Hadal Seabed
Type: Journal Article
Southern Baffin Island mean annual precipitation isotopes modulated by summer and autumn moisture source changes during the past 5800 years
Gorbey DB; Thomas EK; Crump SE; Hollister K; Raynolds MK; Raberg JH; Sepulveda J; Miller GH; De Wet G...
- Gorbey DB
- Thomas EK
- Crump SE
- Hollister K
- Raynolds MK
- Raberg JH
- Sepulveda J
- Miller GH
- De Wet G
Publication Date: 2021-11-03
Type: Journal Article
Bacterial and archaeal lipids trace chemo(auto)trophy along the redoxcline in Vancouver Island fjords
Publication Date: 2021-09-01
Type: Journal Article
Carbon Cycling During Oceanic Anoxic Event 2: Compound-Specific Carbon Isotope Evidence From the Western Interior Seaway
Publication Date: 2021-09-01
Type: Journal Article
Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments
Publication Date: 2021-06-17
Type: Journal Article
Ancient plant DNA reveals High Arctic greening during the Last Interglacial
Crump SE; Frechette B; Power M; Cutler S; de Wet G; Raynolds MK; Raberg JH; Briner JP; Thomas EK; Sepulveda J...
- Crump SE
- Frechette B
- Power M
- Cutler S
- de Wet G
- Raynolds MK
- Raberg JH
- Briner JP
- Thomas EK
- Sepulveda J
Publication Date: 2021-03-30
Type: Journal Article
A source of isotopically light organic carbon in a low-pH anoxic marine zone
Vargas CA; Cantarero SI; Sepulveda J; Galan A; De Pol-Holz R; Walker B; Schneider W; Farias L; Cornejo D'Ottone M; Walke...
- Vargas CA
- Cantarero SI
- Sepulveda J
- Galan A
- De Pol-Holz R
- Walker B
- Schneider W
- Farias L
- Cornejo D'Ottone M
- Walker J
Publication Date: 2021-03-11
Type: Journal Article
Response of biological productivity to North Atlantic marine front migration during the Holocene
Publication Date: 2021-02-08
Type: Journal Article
Diverse origins of "soil marker" bacteriohopanepolyols in marine oxygen deficient zones
Publication Date: 2021-01-01
Type: Journal Article
Marine organic carbon burial increased forest fire frequency during Oceanic Anoxic Event 2
Publication Date: 2020-10-01
Type: Journal Article
Size-Fractionated Contribution of Microbial Biomass to Suspended Organic Matter in the Eastern Tropical South Pacific Oxygen Minimum Zone
Cantarero SI; Henriquez-Castillo C; Dildar N; Vargas CA; von Dassow P; Cornejo-D'Ottone M; Sepulveda J...
- Cantarero SI
- Henriquez-Castillo C
- Dildar N
- Vargas CA
- von Dassow P
- Cornejo-D'Ottone M
- Sepulveda J
Publication Date: 2020-09-22
Type: Journal Article
Analytical and Computational Advances, Opportunities, and Challenges in Marine Organic Biogeochemistry in an Era of "Omics"
Steen AD; Kusch S; Abdulla HA; Cakic N; Coffinet S; Dittmar T; Fulton JM; Galy V; Hinrichs K-U; Ingalls AE...
- Steen AD
- Kusch S
- Abdulla HA
- Cakic N
- Coffinet S
- Dittmar T
- Fulton JM
- Galy V
- Hinrichs K-U
- Ingalls AE
Publication Date: 2020-09-02
Type: Journal Article
Pages
Teaching
Join us
Interested in joining the new Organic and Isotope Geochemistry Group as a student or postdoc? Contact Prof. Julio Sepúlveda directly for current opportunities.
Courses
- GEOL 4700/5700-008: Organic Geochemistry
- This course explores the “biomarker concept” as a tool to elucidate biogeochemical and climatic processes in natural systems through four fundamental questions: How can we characterize and classify organic molecules in complex, natural mixtures? What processes control the synthesis, preservation and destruction of organic matter in nature? How can we use lipid biomarkers to study biogeochemical processes in modern and ancient systems? How can biomarkers inform us about Earth’s past climate and biota.
- GEOL 5700-030: Geological Topics Seminar: Lipid Biomarkers in the Geosciences
- Recent analytical advances in organic and stable isotope geochemistry have revolutionized the Earth Sciences by providing an ever-growing number of tools to study the complex interplay between biology, biogeochemistry, geology and climate at different time scales. This course for graduate students explores hot topics in lipid biomarker and compound-specific stable isotope research. Compared to the regular Organic Geochemistry class (GEOL 4700-003/5700-0044), this course will be conducted in seminar format with interspersed small background lectures, and with a stronger focus on specific applications in the Earth Sciences. We will read and discuss seminal and recent research papers that are expanding our understanding of how our planet works, and how it has changed since the emergence of life.
- GEOL 3040: Global Change: The recent geological record
- This course for undergraduate students explores the science of global change with a focus on how the geological record can inform the study of future climate change. We discuss the basics of the global climate system, how the climate of our planet has changed over geological time scales due to natural processes, and how it has changed and will continue to change due to human impact. Students will learn: (a) How the climate system works; (b) What factors cause climate to change across different time scales; (c) How scientists use different archives (records) and tools (proxy or proxies) to study climate change in the past (paleo-climate); (d) How scientists use observations, models, and theory to make predictions about future climate change and its consequences for our planet.
Current students
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Outreach
In a TED-style talk, Julio shares how he came to investigate the tiny microbes that fill our oceans. He describes what they can tell us about climate through time, the impact of climate change on the ecosystems that depend on these microbes, and how we can all contribute to protecting our oceans and planet. Julio’s talk was part of CU Boulder's annual Research & Innovation Week, where the 2022 Faculty Fellows gave short talks at the Dairy Arts Center in Boulder.