This dataset provides the abundance, functional traits and stable isotopes (δ13C, δ15N, and δ34S) of species colonizing slate- and wood-substrata blocks deployed along an hydrothermal vent gradient at and away from the Eiffel Tower edifice (~1,700m depth, Lucky Strike vent field, Mid-Atlantic Ridge).

The present dataset is provided as an Excel file (.xls) and includes 6 sheets: information of colonizing blocks and environmental conditions (block_env sheet), species abundances (species_abundances), definitions of functional traits (trait_def sheet) and species functional traits (traits sheet), species stable isotopes (stable_isotopes sheet) and references associated with this dataset (reference sheet). Note that species abundances are given as the sum of individuals found in the macrofaunal compartment and the extrapolated abundances of individuals found on the meiofaunal compartment (see below for more details). 

Substrata consisted of size-standardized slate and wood blocks (10x10x10 cm) deployed for 2 years at four different “sites” characterized by a decreasing level of hydrothermal activity (“active,” “intermediate,” “periphery,” and “far”). In short, the active site is located near a vigorous venting activity on the Eiffel Tower edifice, the intermediate site is located further down on the western side of the edifice, in an area of diffuse flow. Both the active and intermediate sites are colonized by dense Bathymodiolus azoricus mussel beds. The periphery site is situated on a sedimentary area with no hydrothermal activity between the Eiffel Tower (~50 m) and Montségur edifices (~85 m). The far site is situated on a basaltic seabed with no hydrothermal activity on the west side of the Lucky Strike lava lake, at ~90, ~120, and ~470 m away from the Helen, Pico and Eiffel Tower active edifices, respectively. Three blocks of slate and wood were deployed at each of the four sites. Colonizing blocks were deployed during the MoMARSAT 2013 cruise, and recovered during the MoMARSAT 2015 both on board the R/V Pourquoi pas? using the ROV Victor6000.

Blocks were washed with filtered seawater and sieved through 300- and 20-µm meshes. Sieved samples were sorted manually under a stereo microscope and all taxa were counted and identified to the lowest taxonomic level possible. The 300-µm samples were completely sorted. The 20-µm samples were transferred to 200-ml beakers and three subsamples of 5 ml each were taken from the original volumes. For each subsample, we identified individuals to the lowest possible taxonomic level and extrapolated the average number of individuals per subsample to the original sample volume, and summed to the 300-μm sample abundances. Three biological response traits related to energy availability and environmental stress, namely adult mobility, maximum body size and feeding strategy, each comprising several modalities, were measured and/or obtained from the literature for each species. The δ13C, δ15N and δ34S isotope ratios of 42 species were analyzed.

More details of the study area, experimental setup, sample processing, species sorting and identification, functional traits and isotopes can be found in Alfaro-Lucas et al. Ecology (2020).