Award: OCE-1948580

When life at deep-sea hydrothermal vents was discovered almost 50 years ago, people were captivated by these islands of life in the dark, otherwise relatively barren deep seafloor. Decades of research at hydrothermal vents have shown that the larvae of endemic vent animals disperse effectively between vents, yet we don't know how they complete their journey by finding and settling in the right spot. This question has remained one of the key unresolved puzzles in the ecology of deep-sea hydrothermal vents. Vent-specific cues must provide dispersing vent larvae with signposts to their specialized benthic homes, yet few experiments have tested larval responses to cues at vents.

Many marine invertebrates use microbial biofilms to choose settlement sites, though the exact cues are unclear. Hydrothermal vents are good place to study questions about the roles of biofilms in larval settlement because vent biofilms are relatively simple; vent animals strictly depend on vent microbes, often through symbiotic partnerships that are acquired at settlement; and variations in habitat types and geochemical gradients are present within a common larval pool. Because of the inextricable linkages between microbes and endemic vent animals, we performed a set of field experiments to test whether microbial biofilms integrate the temporal variability present in dynamic vent ecosystems, thereby providing settling larvae with a signpost pointing toward suitable habitat.

Our initial field work shows foundational vent mussels prefer to settle on older, well-established biofilms (Ladd et al. 2024). Follow-up field experiments indicate that other common animals at hydrothermal vents, including some snails and worms, also settle on the more established biofilms. Established biofilms host distinct microbial communities (Ladd et al. 2024) and higher microbe densities than younger films (Heimbichner-Goebel MS thesis, in prep). Lab trials further suggest microbes can alter swimming behavior in some gastropod larvae (Zúñiga Mouret et al. 2025). We are now working in collaboration with researchers at Rutgers University to identify the molecular components of the biofilm that may be cuing larval settlement. Together, these results provide the first explicit evidence that microbial biofilms cue larval settlement at deep-sea hydrothermal vents. 

These pioneering results further our understanding of mechanisms and processes impacting how endemic invertebrates at hydrothermal vents build communities in an extreme and variable environment. Answering questions about the drivers of initial settlement of animals at hydrothermal vents has become urgent as these ecosystems are increasingly becoming targets for exploitation of precious metals. The work also informs general questions about larval settlement across marine ecosystems and may have applications for antifouling strategies.

This project also provided important educational and outreach opportunities. Arellano solicits lab group members with little prior research experience, whether they are undergraduates or master’s students, and trains them to become scientists in any field by focusing on transferable skills. This project supported a postdoctoral researcher with no previous deep-sea research experience who has now developed all the skills necessary to build her own deep-sea research program, four Master’s students with little prior research experience or no prior deep-sea research (one of whom completed a thesis associated with this project that explored the symbiotic relationship between a mussel and worm; Lemke 2025), two inexperienced REU interns, a post-baccalaureate technician who used this experience in part to earn an NSF-GRFP and to complete MS research in deep-sea ecology, and three undergraduate assistants hoping to gain experience with marine science techniques. We’ve also created an undergraduate community-ecology lab module usable in courses on deep-sea ecology, statistics, and microbial ecology. Finally, we are finishing a feature-length documentary, co-produced with students through the Immersive Learning through Science Storytelling Lab at Rutgers, to share this research with a broad audience.

Ladd TM, Selci M, Davis DJ, Cannon O, Plowman CQ, Schlegel I, Inaba A, Mills SW, Vetriani C, Mullineaux LS, Arellano SM (2024) Faunal colonists, including mussel settlers, respond to microbial biofilms at deep-sea hydrothermal vents. Deep Sea Research Part I: Oceanographic Research Papers, 208:104314. https://doi.org/10.1016/j.dsr.2024.104314

Zúñiga Mouret R, Hourdez S, Curran M, DiBenedetto MH, Mills SW, Vetriani C, Arellano SM, Weston JNJ, Dykman LN, Best AC, Pires A, Mullineaux LS (2025) Pressurized plankton observatory offers a new window into deep‐sea larval behavior. Limnology and Oceanography: Methods, https://doi.org/10.1002/lom3.10708

Lemke, Mel, "Ecology and symbiosis of Branchipolynoe symmytilida and Bathymodiolus thermophilus at East Pacific Rise hydrothermal vents." (2025). MS Thesis. WWU Graduate School Collection. 2482.
https://mabel.wwu.edu/do/9e0059e1-9532-4c90-85a0-1fc2a3ed9912

Heimbichner-Gobel, Wyatt. “Larval settlement as a function of physical characteristics of microbial biofilms.” (In prep.) MS Thesis. Western Washington University.

Last Modified: 04/12/2026
Modified by: Shawn M Arellano