LOCEAN has been in charge of collecting sea water for the analysis of water isotopes on a series of cruises or ships of opportunity mostly in the equatorial Atlantic, in the North Atlantic, in the southern Indian Ocean, in the southern Seas, Nordic Seas, and in the Arctic. The LOCEAN data set of the oxygen and hydrogen isotope (δ18O and δD) of marine water covers the period 1998 to 2019, but the effort is ongoing. Most data prior to 2010 (only δ18O) were analyzed using isotope ratio mass spectrometry (Isoprime IRMS) coupled with a Multiprep system (dual inlet method), whereas most data since 2010 (and a few earlier data) were obtained by cavity ring down spectrometry (CRDS) on a Picarro CRDS L2130-I, or less commonly on a Picarro CRDS L2120-I. Occasionally, some data were also run by Marion Benetti on an Isoprime IRMS coupled to a GasBench (dual inlet method) at the university of Iceland (Reykjavik). On the LOCEAN Picarro CRDS, most samples were initially analyzed after distillation, but since 2016, they have often been analyzed using a wire mesh to limit the spreading of sea salt in the vaporizer. Some of the samples on the CRDS were analyzed more than once on different days, when repeatability for the same sample was not sufficient or the daily run presented a too large drift. Accuracy is best when samples are distilled, and for δD are better on the Picarro CRDS L2130-I than on the Picarro CRDS L2120-I. Usually, we found that the reproducibility of the δ18O measurements is within ± 0.05 ‰ and of the δD measurements within ± 0.30 ‰, which should be considered an upper estimate of the error on the measurement on a Picarro CRDS. The water samples were kept in darkened glass bottles (20 to 50 ml) with special caps, and were often (but not always) taped afterwards. Once brought back in Paris, the samples were often stored in a cold room (with temperature close to 4°C), in particular if they were not analyzed within the next three months. There is however the possibility that some samples have breathed during storage. We found it happening on a number of samples, more commonly when they were stored for more than 5 years before being analyzed. We also used during one cruise bottles with not well-sealed caps (M/V Nuka Arctica in April 2019), which were analyzed within 3 months, but for which close to one third of the samples had breathed. We have retained those analyses, but added a flag ‘3’ meaning probably bad, at least on d-excess (outside of regions where sea ice forms or melts, for the analyses done on the Picarro CRDS, excessive evaporation is usually found with a d-excess criterium (which tends to be too low); for the IRMS analyses, it is mostly based when excessive scatter is found in the S- δ18O scatter plots or between successive data, in which case some outliers were flagged at ‘3’). In some cases when breathing happened, we found that d-excess can be used to produce a corrected estimate of δ18O and δD (Benetti et al., 2016). When this method was used a flag ‘1’ is added, indicating ‘probably good’ data, and should be thought as not as accurate as the data with no ‘correction’, which are flagged ‘2’ or ‘0’. We have adjusted data to be on an absolute fresh-water scale based on the study of Benetti et al. (2017), and on further tests with the different wire meshes used more recently. We have also checked the consistency of the runs in time, as there could have been changes in the internal standards used. On the Isoprime IRMS, it was mostly done using different batches of ‘Eau de Paris’ (EDP), whereas on the Picarro CRDS, we used three internal standards kept in metal tanks with a slight overpressure of dry air). The internal standards have been calibrated using VSMOW and GISP, and were also sent to other laboratories to evaluate whether they had drifted since the date of creation (as individual sub-standards have typically stored for more than 5-years). These comparisons are still not fully statisfactory to evaluate possible drifts in the sub-standards. Version V5 contains only one global file (ALL-Wisotopes-V5). However, up to version V4, individual files corresponded to regional subsets : - SO: Southern Ocean including cruise station and surface data mostly from 2017 in the Weddell Sea (WAPITI Cruise JR160004, DOI:10.17882/54012), as well as in the southern Ocean south of 20°S - SI: OISO cruise station and surface data in the southern Indian Ocean (since 1998) (DOI:10.18142/228) - EA: 20°N-20°S cruise station and surface data (since 2005), in particular in the equatorial Atlantic from French PIRATA (DOI:10.18142/14) and EGEE cruises (DOI:10.18142/95) - NA: 20°N-72°N station and surface data, mostly in the North Atlantic from Oceanographic cruises as well as from ships of opportunity (this includes in particular OVIDE cruise data since 2002 (DOI:10.17882/46448),  CATARINA, BOCATS1 and BOCATS2 (PID2019-104279GB-C21/AEI/10.13039/501100011033) cruises funded by the Spanish Research Agency, RREX2017 2017 cruise data (DOI:10.17600/17001400), SURATLANT data set since 2011 (DOI:10.17882/54517), Nuka Arctica and Tukuma Arctica data since 2012, STRASSE (DOI:10.17600/12040060) and MIDAS cruise data in 2012-2013, as well as surface data from various ships of opportunity since 2012) - NS: Nordic Sea data from cruises in 2002-2018 - AS: Arctic Ocean north of 72°N, in particular from two Tara cruises (in 2006-2008 and 2013) and expeditions since 2020 - PM: miscellaneous data in tropical Pacific, Indian Ocean, Mediterranean Sea and Black Sea In some regions, such as in the Indian Ocean, it is valuable to combine different subsets to have the full data distribution. The files are in csv format reported, and starting with version V1, it is reported as: - Cruise name, station id, bottle number, day, month, year, hour, minute, latitude, longitude, pressure (db), temperature (°C), it, salinity (pss-78), is, dissolved oxygen (micromol/kg), io2, δ18O, iO, d D, iD, d-excess, id, method type - Temperature is an in situ temperature - Salinity is a practical salinity it, is, io2, iO, iD, id are quality indices equal to: - 0 no quality check (but presumably good data) - 1 probably good data - 2 good data - 3 probably bad data - 4 certainly bad data - 9 missing data (and the missing data are reported with an unlikely missing value) The method type is 1 for IRMS measurements, 2 for CRDS measurement of a saline water sample, 3 for CRDS measurement of a distilled water sample.

This dataset gathers isotopic ratios (carbon and nitrogen) and concentrations of both priority (mercury species and polychlorinated biphenyls congeners) and emerging (musks and sunscreens) micropollutants measured in a host-parasite couple (hake Merluccius merluccius muscle and in its parasite Anisakis sp) from the south of Bay of Biscay in 2018. In addition, the hake infection degree measured as the number of Anisakis sp. larvae was added for each hake collected.

This dataset gather isotopic ratios (carbon and nitrogen) and concentrations of mercury species (methyl and inorganic mercury) measured in several tissues (muscle, liver and gonad) for three commonly consumed fish species from the south Bay of Biscay (France) in 2017 and 2018.

Physical data associated with the ABRACO2 cruise. The ABRACOS2 cruise's main objective was to draw up a 3D characterisation of the abiotic and biotic compartments and their interactions. The cruise had 3 specific objectives: 1) Characterisation of water masses and their dynamics. Data collected (ADCP, CTD, rosette, etc.) will be used to study the physical connections between (i) ocean islands and coastal ecosystems and (ii) tropical/subtropical coastal regions to the South and equatorial coastal regions to the North. In-situ measurements will also make it possible to validate the regional high-resolution hydrodynamic models. 2) Ecosystem acoustics. Collecting multifrequency acoustic data in order to create the first 3D characterisation of island and coastal ecosystems in the Northeast Region of Brazil. Acoustic observations will be combined with sampling with pelagic trawl (Legs 1 and 2), bottom trawl (Leg 1), and with sampling of zooplankton and video images. 3) Biodiversity and food web structure. In-situ sampling will provide information about the distribution, biodiversity, trophic ecology (use of stable isotopes) and the contamination (methylmercury) of organisms. The related projects are ABRAÇOS and 'Planning in a liquid world: Marine spatial planning and network dynamics' (PADDLE), (H2020 RISE), (PI: M. Bonnin, 2017-2020).

The diet and stable isotopic (i.e. δ15N and δ13C values) compositions of eels have been studied during each season of 2019 with a fyke net in six estuaries located along the French coast of the eastern English Channel (Slack, Wimereux, Liane, Canche, Authie and Somme estuaries) (10.1371/journal.pone.0270348).

Three saltmarshes, Aiguillon, Brouage, Fier d'Ars, located in the Pertuis-Charentais Sea along the south-west coast of France, were studied to evaluate their sediment and mass accumulation rates (SAR; MAR) based on 210Pb and 137Cs profiles in sediments. Coastal saltmarshes play indeed an essential role in providing services such as coastal protection and supporting biodiversity. Saltmarshes are also critical environments for the accumulation of sedimentary organic carbon (blue carbon). However, the number of studies on saltmarshes remains underrepresented compared to studies on mangroves and seagrass. This work is a contribution to the effort to document sediment and mass accumulation rates of saltmarshes.A total of 16 1m sediment cores were collected in the three saltmarshes (Aiguillon, Brouage, Fier d'Ars) in 2021 and 2022 using an Eijkelkamp stainless steel peat sampler. Each sediment core was sampled every 1 cm from the top to the bottom of the core. The sediment layers were used to determine dry bulk density and selected radioisotope activities (210Pb, 226Ra, 137Cs, 228Th, 137Cs). Combining excess 210Pb and 137Cs has allowed to establish a reliable chronology of sediment deposition on a multidecadal timescale.

Ages obtained through the 40Ar/39Ar method for basalt samples with the Nautile submersible along the axis of the Mid-Atlantic Ridge south of the Romanche transform fault. Major elements measurements were performed on the same samples. For a complete description of the method and discussion of results, please refer to the Grenet et al. 2023 article.

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).