This fall, Rhegan Thomason joins our group to complete her PhD in the EPSS Geochemistry Program.
Rhegan received her Bachelor of Science in Biological Sciences from the University of Texas at El Paso. Her research interests focus on marine microbial ecosystems, biogeochemical cycles, and how environmental changes impact marine life. Recently, she worked as an NSF C-CoMP Bridge-to-PhD Fellow at Woods Hole Oceanographic Institute, using ecosystem models to study how physical and biogeochemical factors influence heterotrophic marine bacteria. She has also researched the effects of ocean acidification and eutrophication on shellfish in Massachusetts estuaries.
For her graduate studies in our group, Rhegan will be involved in reasearch on the marine microbial methane cycle.
In May and June of 2024, my research group embarked on an NSF-funded expedition to explore methane seeps in the Aleutian Trench off Alaska. Our mission was to investigate the role of methane-derived carbon in deep-sea ecosystems as part of the ongoing ‘Methanosphere’ project. This expedition, the second of the project, was led by Dr. Lisa Levin from Scripps Institution of Oceanography, with Co-PIs Dr. Victoria Orphan (Caltech), Dr. Shana Goffredi (Occidental College), and myself.
We targeted methane seeps located at depths between 2000 and 5000 meters off the Aleutian Islands, and thanks to the newly enhanced deep-dive capacity of the Alvin submersible, which now reaches 6500 meters (up from its previous limit of 4500 meters), we were able to push the boundaries of exploration. Our team had the privilege of being the first scientific group to utilize Alvin’s expanded capabilities for research, allowing us to delve deeper into these remote and poorly understood environments.
During our 2024 expedition, we explored three key sites: EDGE, SHUMAGIN, and SANAK. The EDGE and SHUMAGIN sites hold a special place in deep-sea exploration, as they were first discovered 30 years ago by Dr. Erwin Suess’s group from GEOMAR in Germany. These were the deepest locations we visited, with water depths ranging from 4700 to 5000 meters.
A particularly meaningful moment for our team was revisiting the former sampling sites of Dr. Suess’s group. In honor of his incredible contributions to marine science, we deployed a memorial rock for Dr. Suess, who sadly passed away on September 28, 2023. You can read a special article about the memorial rock deployment and his research legacy on the GEOMAR website.
In an unexpected twist, we found no massive outcropping carbonate structures at these deep sites, which suggests that carbonates may dissolve back into the ocean water below the carbonate compensation depth—a discovery that could add new insights into the carbon cycle in deep-sea environments.
The SANAK site, our shallowest at approximately 2000 meters, was a recent discovery by NOAA and stands out for its extensive carbonate structures and thriving tubeworm fields. As we began sampling, we were met with an unexpected phenomenon—a major marine snowstorm. This flurry of organic particles falling from the surface added a layer of complexity to our study, sparking questions about the seasonality of carbon supply to this seep ecosystem. The presence of such a substantial carbon flux during our visit could have important implications for understanding the temporal dynamics of food sources for deep-sea communities like the one at SANAK.
Everyone on board was filled with excitement and anticipation as we studied these unique deep-sea habitats. We are incredibly grateful for the unwavering support and expertise provided by the Alvin and Atlantis teams, without whom this research would not have been possible. Their dedication played a crucial role in making this expedition a success, and we deeply appreciate their contributions to advancing our understanding of these remarkable environments.
Departing from Kodiak Island aboard the RV Atlantis, with the pilot boat alongside on the left, we set off on our next scientific adventure.
Submersible Alvin is launched for a dive to the deep-sea methane seeps.
Inside Alvin during a dive. Happy divers 🙂
Methane seep communities (symbiotic frenulate worms and clams) at the SHUMAGIN seep at about 4880 m.
Marine snowstorm over a tubeworm field at the SANAK methane seep (2000 m).
Orange sulfur bacteria mat collected with an Alvin pushcore at the SANAK seep.
Subsampling of a sediment push core collected by Alvin.
Authigenic carbonate rock from the SANEK seep, formed through intense microbial activity associated with the anaerobic oxidation of methane (AOM) in the sediment. These rocks serve as habitats for a variety of organisms, both within and on the surface, highlighting the intricate relationship between microbial processes and deep-sea ecosystems.
Sawing of methane carbonate rocks for incubations and analyses.
Alkalinity titration of porewater collected from sediment cores.
Collection of water samples to study methane and microbial methane oxidation in the water column.
Foam cup before/after diving with Alvin: Crushed by the pressure at 2000 m.
UCLA Team with student trainee from the Alaska Native Science & Engineering Program (from left to right): Stefani Martinez (ANSEP), George Vetushko, Jiarui Liu, Dr. Kira Homola, Emily Klonicki, Dr. Tina Treude.
PIs with the Suess Memorial Rock (from left to right): Dr. Shana Goffredi, Dr. Victoria Orphan, Dr. Tina Treude, Dr. Lisa Levin (Chief Scientist).
Congrats to my master student George Vetushko, who received the NSF Graduate Research Fellowship, and my graduate student Jiarui Liu, who received the UCLA Dissertation Year Fellowship. You both Rock!
Big congratulations to my two graduate students DJ and De’Marcus, who both defended their thesis on April 29 and graduated end of spring. Both worked on biogeochemical processes related to the oxygen minimum zone in the Santa Barbara Basin.
This Fall, George Vetushko, (re)joins our group as graduate student to complete a master in EPSS. George received his Bachelor of Science in Astrobiology at UCLA. While at UCLA as an undergraduate student, George led an undergraduate team of students in modeling Southern Californian fugacious coastal lagoon environments from aerial data and in-field sampling supervised by Dr. Dave Jacobs (EEB). He further completed a research-oriented course in radar astronomy alongside Dr. Jean-Luc Margot (EPSS) parsing through potential technosignatures from SETI data and classifying patterns of radiointerference. In our group, George completed a senior undergraduate thesis on the coupling of anaerobic oxidation of methane to nitrate reduction in a Southern California wetland. George further supported our group as undergraduate researcher in the lab and onboard the RV Atlantis during our 2023 expedition to the Santa Barbara Basin.
For his graduate studies in our group, George plans to continue his work on climate-change related trends in the coupling of anaerobic oxidation of methane to nitrate reduction in coastal wetland environments.
End of June 2023, our group set ‘sail’ to participate in two back-to-back marine research expeditions onboard the research vessel Atlantis (AT50_11 and _12), which hosts the famous deep-sea submersible Alvin. The total length of the two expeditions, which were supported by the National Science Foundation and organized by the Woods Hole Oceanographic Institution, was over 5 weeks and took us to two different types of marine environments off the coast of southern California.
The first expedition (AT50_11) focused on microbial processes in the oxygen minimum zone of the Santa Barbara Basin. High productivity of plankton in the surface water and weak ventilation of the deep basin water triggers a strong decline of oxygen when bacteria feed on decaying planktonic biomass. The degradation of the organic material at the seafloor initiates a complex set of microbial and chemical processes, including the development of massive sulfur bacteria mats, which feed on hydrogen sulfide produced in the sediment. While most of these processes are natural, we are also interested to understand potential intensification and alteration of the processes related to human impacts such as climate change. For our research, we descended to the seafloor (maximum depth around 590 m) with the submersible Alvin for the deployment of chambers to measure fluxes of chemicals (such as oxygen, nitrate, sulfide) into and out of the sediment. Further analytical support was provided by the cute autonomous underwater vehicle (AUV) Sentry, which completed several pre-programmed dives through the Santa Barbara Basin without a pilot to measure oxygen distribution and to monitor seafloor coverage of the sulfur bacteria mats. This NSF-funded expedition was a collaboration with the UC Santa Barbara (Dr. David Valentine), the Alfred Wegener Institute in Germany (Dr. Felix Janssen), and the Mt. San Antonio College (Dr. Tania Anders)
The second expedition (AT50_12) aimed at cold seeps that release fossil methane from the seafloor. Cold seeps are found at many locations off the coast of southern California (Malibu, Santa Monica, Redondo Beach, Palos Verdes, San Pedro, Del Mar) and seepage is often facilitated through migration of methane along tectonic fault systems. The methane serves as an energy and carbon source for many organisms and creates special cold seep communities. The seep ecosystem usually starts with microbes, who feed on the methane and provide biomass for other organisms higher up in the food chain. The overall aim of the project was to understand the connectivity between methane and organisms and the importance of cold seeps for the overall health of the deep-sea ecosystem. On our dives to the up to 1000 m deep methane seeps, we collected seep rocks (carbonates made from methane-derived carbon) and sediments to study methane-eating microbes and animals associated with this ecosystem. This NSF-funded expedition was a collaboration with the Scripps Institute of Oceanography (Dr. Lisa Levin), the Occidental College (Dr. Shana Goffredi) and Caltech (Dr. Victoria Orphan).
Diving with a deep-sea submersible such as Alvin is a dream come true for many marine scientists. It is not unlike boarding a spaceship – only few people in the world get a chance to experience it. Before boarding the submersible, scientists receive a safety training and must obey several safety rules, such as only wearing flame-resistant clothes and leaving any non-tested electronics such as cellphones behind. All Alvin pilots are Navy-trained and the solid titan sphere that holds the humans is approved for dives up to 6,500 m (21,325 feet). Once on board (usually two scientists and one pilot), everyone gets busy quickly to make sure samples requested are taken and documented with video cameras. The usual 6-8 hours in the sub fly by quickly. For the hungry ones, lunch boxes with sandwiches and chocolate are provided – so is a ‘toilet’ in the form of a plastic bottle. If people get asked what their most memorable moment in the submersible was, many mention the bioluminescence (glow) of organisms in the darkness of the deep sea. Once returned to the surface, those who experienced their first Alvin dive are welcomed back by the science crew with a bucket of ice-cold water, a joyful ceremony known as the ‘Alvin baptism’.
Next year, in late spring 2024, our group will get closer to Alvin’s dive limit when we will explore methane seeps off Kodiak Island (Alaska) at depths up to 5,500 m. Data gained during this future expedition will be compared to data from the shallower southern Californian seeps to study shifts in the relevance of methane for the ecosystems relative to water depth.
Watch also the ‘Women of the Deep’ video produced by Lisa Levin’s group on YouTube.
This fall, Dr. Kira Homola joins our group for two years to work with us on our NSF-funded methane seep project. Kira received the prestigious NSF postdoctoral research fellowship. In her project, she will assess how much of the carbon captured when rocks form at deep ocean methane seeps is released back into the water column over time due to biomediated corrosion.
Born in Hawaii, Kira grew up in the Salish Sea of Washington state where she fell in love with the ocean and natural world. In 2013, she completed two bachelors of science degrees from the University of Washington (UW), one in mechanical engineering and one in oceanography with a minor in climate science. During her three years at UW, she was able to spend four months at sea on oceanographic expeditions. She continued her studies at the University of Rhode Island with the lab groups of Dr. Art Spivack and Dr. Rebecca Robinson. In 2020, she completed her PhD in Oceanography on the fate of atmospheric carbon in ancient oceans and the temperature and pressure limits of microbial life using techniques including porewater geochemistry and thermodynamic modeling.
This summer our group conducted three different fieldwork activities. We had a lot of fun in the outdoors and collected tons of samples and data that will keep us busy for the next months.
Fieldwork Activity 1: Santa Barbara Basin with the R/V Shearwater
End of July, our group –in collaboration with the group of Dr. David Valentine (UCSB)– went out with the NOAA-operated vessel R/V Shearwater to the Santa Barbara Basin. We deployed a CTD and our miniaturized multicorer to collect data and samples from one of our deepest low-oxygen stations. The main focus of this NSF-funded project is to study the seasonality of sulfur bacteria mats in the Santa Barbara Basin and the underlying biogeochemical processes.
Fieldwork Activity 2: Carpinteria Salt Marsh Reserve
In early August our group visited the Carpinteria Salt Marsh Reserve, which is a UC reserve operated by UCSB, to study methane emission dynamics and collect sediment with a special hand corer. This NSF-funded project studies cryptic methane cycling in the salt marsh sediments, which is the relation between methanogenesis and anaerobic oxidation of methane.
Fieldwork Activity 3: Green Lake, Upstate New York
As part of the NASA ICAR project, and in collaboration with the group of Timothy Lyons (UCR), our group studied microbial processes in the water column and sediment of Green Lake in Upstate New York mid August. The lake is meromictic with a sharp chemocline around 18-20 m water depth. The conditions in the lake are reminiscent of biogeochemical processes in early-Earth oceans and we are interested in understanding the interplay between different microbial processes (mainly sulfate reduction, methanogenesis, and methane oxidation) and geochemistry. Samples were collected from row boats and a Pontoon boat. We had great support and collaborations with the Green Lake Educational Center, Dr. Christopher Junium from Syracuse University, and Dr. Michael McCormick from Hamilton College.
Congrats to De’Marcus Robinson on receiving the 2023 Sea Grant Knauss Fellowship! The Knauss Fellowship provides a unique educational and professional experience to graduate students who have an interest in ocean, coastal and Great Lakes resources and in the national policy decisions affecting those resources.
De’Marcus’s will join 86 finalists to be placed in federal government offices in Washington, D.C. beginning February 2023.
Congratulations to Sebastian Krause for defending his thesis today! Big Day 🙂 We will miss you! All the best for your new postdoc adventure at UCSB with my dear colleague Dave Valentine!