David Layton Valentine (born 1973) is a geochemist, microbiologist and science communicator. He is a Distinguished Professor of Geochemistry and Microbiology in the Department of Earth Science at the University of California, Santa Barbara (UCSB), where he holds the Norris Presidential Chair. At UCSB, he directs the Valentine Lab.
Early life and education Valentine was born in San Diego, California in 1973 to two scientists and grew up in Davis, California. His father, Raymond C. Valentine (1936–2023), was a professor, at UC Davis and scientific founder of Calgene Inc., an early plant biotechnology company known for the development of RoundUp resistant crop plants and the Flavr Savr tomato among others products.
Valentine graduated from Davis Senior High School in 1991 after studying concurrently at UC Davis during his senior year. He then studied Biochemistry and Chemistry at the University of California, San Diego (UCSD), obtaining a B.S. degree in December 1995 and an MS in June, 1996. During his time at UCSD he conducted research with Donald R. Helinski and with Gordon J. F. MacDonald. He also served as Commissioner of Academic Affairs for the Associated Students, for which he received an award for Amazing Service and Dedication, the plaque for which is shown as an Easter egg in the film Out of Plain Sight. He then studied Earth System Science at UC Irvine, receiving his PhD in 2000, where he worked under the supervision of William S. Reeburgh. His Ph.D. thesis was titled "Biogeochemistry of hydrogen and methane in anoxic environments: Thermodynamic and isotopic studies". Valentine received an NSF Postdoctoral Fellowship in Microbial Biology that same year to conduct research at Scripps Institution of Oceanography, working with Douglas Bartlett and Miriam Kastner.
Career and research Valentine was hired onto the faculty at UC Santa Barbara in July, 2001, at the age of 27. He was promoted to associate professor in 2006, and then professor in 2010, and distinguished professor in 2022. He served as chair of the Interdepartmental Graduate Program in Marine Science from 2021 to 2024, and has been the director of the Marine Science Major from 2018- and the vice chair of the UC Santa Barbara Academic Senate from 2024. He was awarded the Norris Presidential Endowed Chair in Earth Science in 2017.
At UC Santa Barbara he has also received more than 20 grants from the National Science Foundation, and serves as the Co-Principal Investigator for the $22m National Science Foundation Biofoundry for Exceptional and Extreme Fungi, Archaea and Bacteria (Ex-FAB) since 2024.
Research Valentine's research is at the disciplinary interface of microbiology, geochemistry and oceanography with ties to bioengineering. He applies tools from molecular microbiology, oceanography and (isotope) geochemistry to study interactions between microbes, chemicals and their environment in mainly marine settings. Much of his early research was on methane, anaerobic microbes, petroleum weathering, and lipid membranes. He also investigates major disasters such as oil spills and DDT pollution both toward understanding the impacts but also as a basic science tool to understand how the ocean responds to chemical and physical changes. He often uses the phrase "discoveries from disasters" to highlight his approach. In speaking about his work on the microbial breakdown of pollutants conducted at Ex-FAB, Valentine said “We’ve got the ability to engineer capabilities that these organisms have evolved over time — to study them, understand them, and perhaps even apply nature’s remedies”.
In addition to this core research, Valentine's scientific work includes – with his collaborators – the discovery of deep sea features including asphalt volcanoes, and a massive microbial ring in the Santa Barbara Channel, the hot tub of despair in the Gulf of Mexico, diversity generating retroelements in archaea and archaeal viruses, the confirmation of a biological hydrocarbon cycle in the ocean, and ash impacts to coastal ocean microbes from wildfire.
In addition to his own research, Valentine has also worked on translating research into policy and communicating science to broad audiences. He served on the National Academy of Sciences Committee on the Effects of Diluted Bitumen on the Environment: A Comparative Study resulting in a 2016 report entitled Spills of Diluted Bitumen from Pipelines: A Comparative Study of Environmental Fate, Effects, and Response. He also served on the National Academy of Sciences Committee on Evaluation of the Use of Chemical Dispersants in Oil Spill Response resulting in a 2020 report entitled The Use of Dispersants in Marine Oil Spill Response. Valentine also gave congressional testimony on the Orange County Oil Spill in 2021.
Valentine has also spoken out about the impacts of federal cuts in science funding, referring to Trump administration proposals as "a full-scale assault on science". He later pointed out that “This model of long-term funding — stable, federal support — that’s what made us the research powerhouse we are today...that model is under threat right now.” In an LA Times Op/Ed about proposed cuts to overhead costs by the Trump administration he opined that "indirect costs support the deep bench of supporting characters and services that enable me, the scientist, to focus on discovery. Without those services, my research enterprise crumbles, and new discoveries with it." In regard to the proposed 2026 changes in uniform guidance proposed by the Trump administration Valentine stated “The changes they have proposed will create chaos for universities and scientists, make it very easy to cancel projects, and will replace the peer review decision process with a political appointee.” He added “I am concerned that the combination of budget cuts and political control will lead to hollowed-out scientific agencies that set aside discovery based on scientific merit and instead follow political whim”.
Deepwater Horizon
Valentine was among a limited number of scientists investigating the fate and transport of methane, natural gas, and oil in the deep ocean environment prior to the Deepwater Horizon oil spill in 2010, and was among the first scientists supported to respond by the National Science Foundation. Along with his colleagues, he published a series of scientific papers describing approaches to quantify the discharge as well as the environmental behavior and impacts of discharged methane, propane (LNG); oil; and dispersant. Valentine described the atmosphere of scientific inquiry on scene at Deepwater Horizon as industrial chaos on a grand scale requiring respirators on for most of the sampling he did close in to the ruptured wellhead.
Valentine also served as a scientific communicator during this event, providing context through media interviews to outlets including the NY Times, and the LA Times, and through Op/Eds and appearances on news shows including the PBS News Hour. In one interview early in the event he correctly predicted that build-up of gas hydrate would lead to failure of a deep-sea containment device, which he has identified as a pivot point in his engagement as a science communicator. Valentine also worked with government officials in the response phase of the event to direct and conduct sampling of the deep subsurface from multiple research vessels, as documented in the New Yorker through the writing of embedded reporter Raffi Khatchadourian. Later Valentine served as an expert for the Trustees of Natural Resource Damage Assessment, which was a component of the settlement agreement for penalties and damages.
Valentine's work during Deepwater Horizon led to some disagreement and controversy. Valentine and his colleagues' publication on the fate of discharged methane created some disagreement among scientists, whereas his paper on the fallout plume of oil from the event created controversy when the responsible party, BP, put out a statement questioning the findings. The controversy around the fallout plume was later resolved when a team led by Jeff Chanton confirmed Valentine's conclusions with alternate methods.
Oil Spills and Offshore Production
Valentine participated in the response to the Refugio Beach Oil Spill, serving as a topical and local area expert for the event's Unified Command. He engaged in the scientific response, identifying submerged oil from the spill, tracking offshore transport of oil that eventually caused beach closures when it came ashore in Los Angeles, and conducting chemical forensics to differentiate spilled oil from natural seeps located nearby. Valentine was embedded within the Unified Command for the response phase and applied his scientific experience in public meetings and press conferences. Following the response phase, Valentine served as an expert for the Refugio Beach Oil Spill Natural Resource Damage Assessment for the State of California, contributing to the settlement agreement between the government and the responsible party, Plains All American Pipeline. Valentine also served as an expert witness testifying for the prosecution in the criminal case against Plains All American Pipeline, for which the corporation received a felony conviction. Valentine further engaged with media and other outlets as a scientific communicator to contextualize this spill event for the public. He has also engaged with other spill events through both research and science communication, most notably including the Orange County Oil Spill in 2021. Valentine has further engaged in the public discussion about oil production offshore California and related subjects.
Offshore waste disposal site
During a 2011 expedition aboard the Research Vessel Atlantis, Valentine and his team used the autonomous underwater vehicle (AUV) Sentry and remotely operated vehicle (ROV) Jason to uncover an industrial waste disposal site located in the deep coastal ocean off Los Angeles. He contacted the LA Times reporter Rosanna Xia to describe the site and its relationship to DDT waste disposal, triggering Xia to conduct a major investigative report. Xia's reporting of Valentine's research triggered substantial scientific and political interest, triggering in turn federal and state funding initiatives as well as a historical investigation by the EPA. Subsequent research by Valentine and by his collaborators has revealed the scope and persistence of the DDT pollution, extensive littering of the seabed in the region with manmade debris targets, and further revealed the likely disposal of low-level radioactive waste in this area. Valentine has also served a scientific communicator on this issue, talking regularly with reporters, policy makers and elected officials, including numerous interviews with the LA Times and appearances on CBS Saturday Morning, and the PBS News Hour. In 2025, Valentine and his team reported that the DDT-contaminated seafloor area exceeded 300 square miles and further provided a possible explanation as to why some barrels exhibit halos.https://www.independent.com/2025/10/09/whats-causing-eerie-halos-around-barrels-on-ocean-floor/ The Santa Barbara Independent. Retrieved 2025-10-13. In 2026, the Ocean Protection and DDT Reduction Act was introduced to the US Congress based in large part on Valentine's work .
The Marine Science Program at UC Santa Barbara