Composition of a one-year-old Riftia pachyptila community following a clearance experiment: Insight to succession patterns at deep-sea hydrothermal vents

In the basalt-hosted hydrothermal vent habitat around 9°50'N on the East Pacific Rise, the vestimentiferan tubeworms Tevnia jerichonana and Riftia pachyptila (Polychaeta: Siboglinidae) commonly settle before the mussel Bathymodiolus thermophilus (Bivalvia: Mytilidae). We removed six aggregations of R. pachyptila and deployed mussels on the cleared sources of diffuse flow to test the effect of the B. thermophilus on the subsequent colonization by the tubeworms. None of the transplanted mussels persisted on the cleared sources of diffuse flow; however, aggregations of R. pachyptila grew in half of the clearances. We collected one of the aggregations of R. pachyptila along with the associated fauna for determination of relative abundance and biomass in this one-year-old community. This aggregation consisted of 647 specimens of R. pachyptila that hosted individuals of 24 species, including small individuals of T. jerichonana and B. thermophilus. The abundance of the associated fauna was numerically dominated by gastropods, and the biomass was dominated by the Alvinellid polychaete Paralvinella grasslei.