Spatial and temporal variations in food web structure from newly-opened habitat at hydrothermal vents.

International audienceTo highlight the spatio-temporal variability of the food web structure of hydrothermal vent fauna from newly-opened habitat, a series of Titanium Ring for Alvinellid Colonization devices (TRACs) was deployed at TICA site on the East Pacific Rise in 2006. This experiment was conducted for periods of 4 days, 13 days and one month and deployments were aligned along a gradient from the basaltic bottom to the vent openings. δ(13)C values of colonists revealed a narrower range of carbon sources in proximity to vent openings in Alvinella pompejana habitat than in Tevnia jerichonana habitat, separated by a distance of four meters. This was possibly due to a spatial change in available food sources with a possible higher contribution of particulate organic matter (POM) to the siboglinid habitat compared to a higher contribution of microbial primary producers such as Epsilonproteobacteria in the alvinellid habitat. Temporal variability was also observed during experimentation in the form of a shift in either δ(13)C and/or δ(15)N values for A. pompejana, Lepetodrilus elevatus, dirivultid copepods and polynoid polychaetes within a one-month window showing first of all, fast tissues turnover and secondly, a possible switch in feeding strategy or food sources. Lepidonotopodium riftense and Branchinotogluma sandersi may have to alternate between detritivorous and predatory feeding strategies. In addition, through the analysis of stable isotope composition of A. pompejana and its episymbionts, we provided evidence that these attached bacteria formed part of the worms' diet during the course of these colonization experiments