Deep-sea hydrothermal vents are populated by dense communities of animals that form symbiotic associations with chemolithoautotrophic bacteria. To date, our understanding of which factors govern the distribution of host/symbiont associations (or holobionts) in nature is limited, although host physiology often is invoked. In general, the role that symbionts play in habitat utilization by vent holobionts has not been thoroughly addressed. Here we present evidence for symbiont-influenced, regional-scale niche partitioning among symbiotic gastropods (genus Alviniconcha) in the Lau Basin. We extensively surveyed Alviniconcha holobionts from four vent fields using quantitative molecular approaches, coupled to characterization of high-temperature and diffuse vent-fluid composition using gastight samplers and in situ electrochemical analyses, respectively. Phylogenetic analyses exposed cryptic host and symbiont diversity, revealing three distinct host types and three different symbiont phylotypes (one ε-proteobacteria and two γ-proteobacteria) that formed specific associations with one another. Strikingly, we observed that holobionts with ε-proteobacterial symbionts were dominant at the northern fields, whereas holobionts with γ-proteobacterial symbionts were dominant in the southern fields. This pattern of distribution corresponds to differences in the vent geochemistry that result from deep subsurface geological and geothermal processes. We posit that the symbionts, likely through differences in chemolithoautotrophic metabolism, influence niche utilization among these holobionts. The data presented here represent evidence linking symbiont type to habitat partitioning among the chemosynthetic symbioses at hydrothermal vents and illustrate the coupling between subsurface geothermal processes and niche availability. chemoautotrophy | symbiosis | endosymbiosis

No abstract

Patterns of succession in Lau Basin hydrothermal vent communities determined with high-resolution imagery and in situ physico-chemical data collected over 4 yr and analyzed within a Geographic Information System show that Alviniconcha snails are a pioneering group, the snail Ifremeria nautilei is a mid-successional species, and the heat-intolerant mussel Bathymodiolus brevior dominates when venting declines. The associated fauna also changes as communities progress through the successional stages, and eventually non-vent-endemic deepsea species appear when venting has mostly subsided. This is a unique example of primary succession in which the primary producers form symbiotic associations with mobile animals, resulting in successional patterns not observed in other systems. I. nautilei dominates newly formed substrates or venting sources where both I. nautilei and Alviniconcha spp. are already established (e.g., by migration), while Alviniconcha spp. seem to be better at colonizing newly active vents (e.g., by settlement) that are remote from colonized vents. Thus, on the scale of a 5-39 m 2 diffuse flow area or a single edifice, the mid-successional species dominates new substrates instead of the pioneering group. These communities are remarkably stable over long time periods relative to other hydrothermal vent regions. In addition to the sequential replacements of species as sites age and overall conditions change, Lau vent animals track changes in vent fluids and relocate themselves when local hydrothermal plumbing changes over small spatial scales.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

We have used solid-state Au/Hg voltammetric electrodes to understand redox and biogeochemical processes in hot spring and deep sea hydrothermal environments. These electrodes are non-specific and have the capability of measuring simultaneously a suite of chemical species including several of the principal redox species involved in early diagenesis (O 2 follows a zero order rate law consistent with photosynthesis as the source of O 2 . These dynamic environments show how kinetic data can be obtained in situ and be used to understand the interactions between biology and chemistry. We know of no other analytical technique that can provide this information in both clear and turbid waters on the time scales (seconds) observed.