Epifaunal community structure associated with Riftia pachyptila aggregations in chemically different hydrothermal vent habitats

Abstract

The vestimentiferan tubeworm Riftia pachyptila (Polychaeta: Sibloglinidae) often dominates early succession stages and high productivity habitats at low-temperature hydrothermal vents on the East Pacific Rise. We collected 8 aggregations of R. pachyptila and the associated epifaunal community at 2 discrete sites of diffuse hydrothermal activity, in December 2001 and December 2002. Because of the high spatial and temporal variability of the biotic and abiotic factors related to hydrothermal vent activity, significant differences in the structure and the composition of the community were expected to occur at the scale of either 1 yr or 500 m distance between very different sites. There was no significant difference in the temperature ranges of the diffuse flow between sites or years, even though the environmental conditions were very different at the 2 sites. At 1 site (Riftia Field), the diffuse hydrothermal fluids had relatively low concentrations of sulfide, low pH, and high concentrations of iron. At the other site (Tica), the diffuse hydrothermal fluids had higher sulfide concentrations, the pH was closer to neutral, and iron was undetectable. The physiological condition of R. pachyptila appeared to reflect the availability of sulfide at each site. However, the structure and the composition of the epifaunal community were remarkably similar between sites and years, with the exception of a few species. Aggregations of R. pachyptila support high local species diversity relative to the surrounding seafloor and high community similarity in different hydrothermal vent habitats.

Endosymbionts escape dead hydrothermal vent tubeworms to enrich the free-living population

“…To estimate how many symbionts may escape after host death and may colonize surfaces in nature, we took the mean density of symbionts we found after half a day under deep-sea conditions on a coverslip and extrapolated this density to the entire inner surface of the incubation vessel (5772.7 mm 2 ) and related the 0.4 g incubated trophosome to the mean symbiont density (3.7 × 10 9 g −1 trophosome) (36) to the mean trophosome weight (15.3 ± 4.9% of total host's wet weight) (60) in a tubeworm with 20 g wet weight (35). To estimate the impact of symbiont release after the waning of vent flux, we extrapolated the minimal release from one worm to the ranges of tubeworm clumps (11 individuals in a small clump covering 0.02 m 2 basalt to 2,000 individuals·m −2 in a large clump) (58,59) reported from this vent region.…”

A biological survey method applied to seafloor massive sulphides (SMS) with contagiously distributed hydrothermal-vent fauna

“…These kinds of studies are becoming more common for biogenic assemblages in the deep sea (e.g. mussel beds: Dreyer et al 2005; tubeworm clumps: Govenar et al 2005).The abundance and biomass of macroand megafaunal invertebrates at active vents allowed for quantitative sampling and analysis, but peripheral vent samples, where faunal abundances were low, were semi-quantitative, with opportunity only to compare between sites and with many taxa tallied by presence or absence within samples.…”

Metabolite uptake, stoichiometry and chemoautotrophic function of the hydrothermal vent tubeworm Riftia pachyptila: responses to environmental variations in substrate concentrations and temperature

“…Riftia is the dominant megafaunal species at many sites, often growing in enormous aggregations and hosting numerous other species such as mussels, polychaete worms, limpets and crabs Shank et al, 1998;Tunnicliffe, 1991;Govenar et al, 2005). Riftia is devoid of a mouth or digestive tract, and possesses intracellular chemoautotrophic bacteria within a vascularized organ called the trophosome (Cavanaugh et al, 1981;Felbeck, 1981).…”