Ecological physiology of the vestimentiferan tubeworm Ridgeia piscesae from diffuse flow environments on the Juan de Fuca Ridge

To determine the growth rates of the long-skinny morphotype of the vestimentiferan tubeworm Ridgeia piscesae in diffuse hydrothermal vent flow habitats, individuals within aggregations were stained using an in-situ tube-marking device. Tube growth was determined by measuring the new growth above the stained area, The ratio of soft-tissue biomass to tube volume was evaluated as a potential indicator of physiological condition. Yearlong deployments of temperature sensors monitored the exposure to diffuse vent flow. Water samples coupled with temperature measurements were used to determine the relationship between hydrothermal fluid temperatures and sulfide concentrations. Based on that relationship, temperature records were then used to describe exposure to hydrothermal vent fluids and availability of sulfide. The temperature data show high microhabitat heterogeneity at short spatial and temporal scales. There also were significant differences in the relationship between vent fluid temperature and sulfide concentration between the sites. There was no relationship between tubeworm size and growth or between condition index and growth. The growth rates were highly variable between individuals in the same aggregation and between vent sites. Conservative longevity calculations resulted in decadal-length age estimates. Differences in growth within and between sites are somewhat correlated with exposure to diffuse vent fluid. This morphotype of R. piscesae can grow slow or fast in response to availability of sulfide and can survive under very low diffuse vent flow with no growth.; A quantitative collection was used to determine microhabitat characteristics within a single aggregation of this morphotype of R. piscesae. The base of the aggregation was composed of root-like, clear and flexible tube sections that are permeable to sulfide. Diffuse hydrothermal vent flow was only visible in the eastern area of the aggregation and vestimentiferans in this area were in significantly better condition than tubeworms elsewhere in the same aggregation. The clumped distribution and very tight clustering of the newly recruited individuals appear to indicate a gregarious settlement behavior. Aggregations of this morphotype of R. piscesae provide a lasting, renewable surface for settlement and colonization, a source of nutrition and an expanded habitat for other fauna in vent environments of the Juan de Fuca Ridge.