Award: OCE-1737382

On January 15, 2022, the Hunga Volcano—a submarine volcano in the Kingdom of Tonga—erupted, blasting a plume of ash and seawater 58 km into the atmosphere. Beneath the ocean surface, landslides and sediment flows reshaped the seafloor (Chaknova et al. 2025). Weeks later, in March–April 2022, our team explored six deep-sea hydrothermal vent fields in the Lau Basin, located 80–220 km west of the Hunga caldera (Fig. 1). Unexpectedly, we found volcanic material had traveled 1.8–2.8 km down into the Lau Basin, blanketing four of the vent fields with up to 1.5 m of “ash” (Figs. 1, 2; Beinart et al. 2024). These vents were previously dominated by large chemosymbiotic animals—species that rely on bacterial symbionts to use chemical energy—including endangered snails (Alviniconcha strummeri, A. boucheti, A. kojimai, and Ifremeria nautilei; Fig. 2b) and mussels (Bathymodiolus septemdierum). At the most heavily buried sites, the vent communities were devastated, with chemosymbiotic animals almost entirely wiped out (Figs. 1, 2).

To understand recovery, we studied the planktonic larvae—the drifting early life stages—of vent animals above the seafloor. Larval communities were sampled using three methods: (1) the autonomous underwater vehicle Sentry with SyPRID samplers to collect water around and above the vents, (2) a McLane Large Volume Water System to sample water among the vent chimneys, and (3) larval settlement tube traps to estimate how many larvae were reaching the seafloor (Fig. 3).

Larval communities collected among the vent chimneys were similar at ash-impacted and unimpacted sites. In contrast, larval communities collected above and around the vent fields differed significantly between ash-covered and unaffected sites (Jimenez 2025). The most impacted vents had more mobile crab larvae, reflecting changes observed in the remaining adult communities (Beinart et al. 2024). Importantly, larvae of key chemosymbiotic species—including all three Alviniconcha snail species and Bathymodiolus mussels—were detected, but larvae of Ifremeria nautilei were conspicuously absent from all samples. This study also marked the first-ever description of larvae from the genus Alviniconcha, a dominant group at hydrothermal vents across the western Pacific and Indian oceans. These findings provide a baseline for understanding recovery potential after large-scale volcanic disturbance.

Our research also advanced understanding of how vent snails develop and acquire their bacterial symbionts. Previous studies showed that Alviniconcha and Ifremeria species are distributed in distinct zones that reflect differences in vent chemistry, suggesting that each snail species is sorted to particular chemical conditions necessary for their symbionts. What remained unclear was when and how this sorting occurs. Because snail larvae do not inherit symbionts from their parents, they must acquire them from the environment during development.

Using microscopy and genetic sequencing of larvae and juveniles, we traced the timing of symbiont acquisition. We further described the development and behavior of the unusual Wáren’s larvae of Ifremeria nautilei—the first new larval form discovered in over 100 years. Our work showed these larvae are released from their mothers without symbionts. Similarly, juvenile Alviniconcha initially take up multiple symbiont types through their mouth and foot tissues; over time, only the appropriate symbionts persist and become localized in the gills (McCartha 2024). These results clarify how microbes, host development, and vent chemistry interact to shape vent communities.

This project also provided meaningful educational and outreach opportunities (Fig. 4). Three undergraduate students from Western Washington University—a primarily undergraduate institution—gained hands-on research experience, with two becoming co-authors on a peer-reviewed publication (Beinart et al. 2024). All three remain in marine science careers. The project also supported five master’s students and trained a postdoctoral researcher new to deep-sea science, who is now building an independent research career. In partnership with the University of Rhode Island’s Inner Space Center, we also developed public and classroom engagement programs.

The Hunga eruption caused a disturbance to hydrothermal vent ecosystems unlike any previously observed, while also profoundly affecting the people of Tonga. Because these vent systems lie in Tongan waters and may be targeted for future mining, our work provides essential baseline data to assess long-term habitat change, ecological recovery, and the risks associated with deep-sea resource extraction.

Beinart, R., S. Arellano, et al. 2024. Deep seafloor hydrothermal vent communities buried by volcanic ash from the 2022 Hunga eruption. Communications Earth & Environment 5(1):254. 

Chaknova, M., T. Giachetti, J. Paredes‐Mariño, A. Soule, A. R. V. Eaton, R. Beinart, M. Crundwell, S. J. Cronin, M. Jutzeler, K. E. Fauria, M. A. Clare, I. A. Yeo, S. Arellano, et al. How Did Westward Volcaniclastic Deposits Accumulate in the Deep Sea Following the January 2022 Eruption of Hunga Volcano? Geochemistry, Geophysics, Geosystems 26(4). 

Jimenez, Vanessa, "Larval Communities at Hydrothermal Vents After the 2022 Hunga Eruption" (2025). WWU Graduate School Collection. 1353.

McCartha, Michelle, "Investigating symbiont acquisition in deep-sea snails using fluorescent in situ hybridization" (2024). WWU Graduate School Collection. 1344.

Last Modified: 12/30/2025
Modified by: Shawn M Arellano