Plunging into the Abyss: Exploring Methane Seeps in the Aleutian Trench with Alvin’s New Deep-Dive Capabilities!

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).