BUSCADOR RECOLECTA

This dataset is composed of 2 files: a database (in csv format) with 695 records of biogeochemical variables (temperature, salinity, oxygen, nutrients, pH and total alkalinity) analyzed in water samples collected at the GIFT time series and a Readme (txt) file that includes a short description of the variables provided., If the dataset is used, please consider citing Flecha et al., (2019) (doi: 10.1038/s41598-019-52084-x)., This data set includes recently published data used to assess the temporal evolution of pH in Atlantic and Mediterranean water masses exchanging at the Strait of Gibraltar (Long:-5.345, Lat: 36.137, Datum:WSG84) during the decade 2005-2015 and to calculate the magnitude of natural and anthropogenic components on total pH changes (Flecha et al., 2019). The database provides measurements of carbon system parameters in water samples collected at 3 stations that form the marine time series GIFT during 26 oceanographic campaigns conducted over the decade 2005–2015. Geographic coordinates of sampling stations are provided. Some physical data (i.e. pressure, temperature and salinity) are also included. During the cruises, a temperature and salinity profile in each station was obtained with a Seabird 911 Plus CTD probe connected to a rosette sampler. Conductivity measurements were converted into practical values of the salinity scale with the UNESCO equation (1986). Seawater was subsequently collected for biogeochemical analysis using Niskin bottles immersed in the oceanographic rosette at variable depths (from 5 to 8 levels) depending on the instant position of the interface between the Atlantic and Mediterranean flows that was identified by CTD profiles. The biogeochemical variables shown in the database are pH in total scale at 25 °C (pHT25), total alkalinity (AT), Dissolved Oxygen (DO) and inorganic nutrients (nitrate, NO3− and Silicate, SiO44−). pHT25 data were obtained by the spectrophotometric method with m-cresol purple as indicator (Clayton & Byrne 1993) with an addition of 0.0047 (DelValls & Dickson, 1998). Samples were taken directly from the oceanographic bottles in 10 cm path-length optical glass cells and measurements were carried out with a Shimadzu UV-2401PC spectrophotometer containing a 25 °C-thermostated cells holder. Samples for AT analysis were collected in 500-ml borosilicate bottles, and poisoned with 100 μl of HgCl2-saturated aqueous solution and stored until measurement in the laboratory. AT was measured by potential titration according to Mintrop et al. (2000) with a Titroprocessor (model Metrohm 794). DO concentration was obtained through automated potentiometric modification of the original Winkler method using the Titroprocessor. Upon collection, flasks were sealed, stored in darkness and measured within 24 h. Water samples (5 mL, two replicates) for inorganic nutrients determination were taken, filtered immediately (Whatman GF/F, 0.7 μm) and stored frozen for later analyses in the shore-based laboratory. Nutrients concentrations were measured with a continuous flow auto-analyzer using standard colorimetric techniques (Hansen & Koroleff 1999). More details on procedures and data structure are given in a single README file (txt). The data are provided as [space] delimitated plain text files., Plan Estatal de I+D+i, European Commission, CSIC. CARBOOCEAN (FP6-511176), SESAME (FP6-036949), CARBOCHANGE (FP7-264879), PERSEUS (FP7-287600), COMFORT (H2020-820989), CTM2006-28141-E/MAR, CTM2016-75487-R., 1 data csv‘GIFT_carbonparameteres_2005_2015.csv’ file and 1 readme.txt file., Peer reviewed

The database provides discrete measurements of carbon system parameters in water samples collected at 3 stations that form the marine time series GIFT during 33 oceanographic campaigns conducted over 2005–2021. Geographic coordinates of sampling stations are provided. Some physical data (i.e. pressure, temperature and salinity) are also included. Moreover, pH data obtained with a SAMI-pH sensor (Sunburst Sensors, LLC)) attached to a mooring line deployed in the Strait of Gibraltar for the years 2016 and 2017 are provided. During the cruises, a temperature and salinity profile was obtained with a Seabird 911Plus CTD probe. Seawater was subsequently collected for biogeochemical analysis using Niskin bottles immersed in an oceanographic rosette platform at variable depths (from 5 to 8 levels) depending on the instant position of the interface between the Atlantic and Mediterranean flows that was identified by CTD profiles. The biogeochemical variables shown in the database are pH in total scale at 25 °C (pHT25), total alkalinity (AT), and inorganic nutrients (phosphate, PO43and Silicate, SiO44−). pHT25 data were obtained by the spectrophotometric method with m-cresol purple as the indicator (Clayton & Byrne 1993). Samples were taken directly from the oceanographic bottles in 10 cm path-length optical glass cells and measurements were carried out with a Shimadzu UV-2401PC spectrophotometer containing a 25 °C-thermostated cells holder. Samples for AT analysis were collected in 500-ml borosilicate bottles, and poisoned with 100 μl of HgCl2-saturated aqueous solution and stored until measurement in the laboratory. AT was measured by potential titration according to Mintrop et al. (2000) with a Titroprocessor (model Metrohm 794 from 2005-2020 and model Metrothm 888 for 2021). Water samples (5 mL, two replicates) for inorganic nutrients determination were taken, filtered immediately (Whatman GF/F, 0.7 μm) and stored frozen for later analyses in the shore-based laboratory. Nutrients concentrations were measured with a continuous flow auto-analyzer using standard colorimetric techniques (Hansen & Koroleff 1999). 2. Methods for processing the data: 3. Instrument- or software-specific information needed to interpret/reproduce the data, please indicate their location: 4. Standards and calibration information, if appropriate: 5. Environmental/experimental conditions: 6. Describe any quality-assurance procedures performed on the data: 7. People involved with sample collection, processing, analysis and/or submission, please specify using CREDIT roles https://casrai.org/credit/: Chief Scientists -I.Emma Huertas/Susana Flecha; Hydro: Who -Susana Flecha/David Roque/Silvia Amaya-Vías/Angélica Enrique; Nuts: Who -Manuel Arjonilla/ Status - final; Silicate and Phosphate Autoanalizer Hansen and Koroleff (1999), This research was supported by the COMFORT project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 820989 (project COMFORT, "Our common future ocean in the Earth system – quantifying coupled cycles of carbon, oxygen, and nutrients for determining and achieving safe operating spaces with respect to tipping points).” Funding was also provided by the European projects CARBOOCEAN (FP6-511176), CARBOCHANGE (FP7-264879), PERSEUS (FP7-287600) and the Junta de Andalucía TECADE project (PY20_00293). The dataset is subject to a Creative Commons License Attribution-ShareAlike 4.0 International. F.F.P. was supported by the BOCATS2 (PID2019-104279GB-C21) project funded by MCIN/AEI/10.13039/501100011033. SAV was supported by a pre-doctoral grant FPU19/04338 from the Spanish Ministry of Science, Innovation and Universities., Peer reviewed

[Description of methods used for collection/generation of data] The database provides discrete measurements of carbon system parameters in water samples collected at 13 stations during 5 campaigns conducted over 2020–2021. Geographic coordinates of sampling stations are provided. Some physical data (i.e. pressure, temperature and salinity) are also included. During the campaigns, temperature, salinity, conductivity, dissolved oxygen and pH were obtained with an EXO TM 2 multiparametric probe sonde. Surface seawater was subsequently collected for biogeochemical analysis. The biogeochemical variables shown in the database are pH in SWS and NBS scale (pH_SWS and pH_NBS), total alkalinity (AT), and inorganic nutrients (nitrite, nitrate, ammonium, silicate and phosphate), Dissolved Organic Carbon (DOC), Suspended Solid Matter (SSM), and chlorophyll a (Chla). · pH_NBS data were obtained by the EXO TM 2 multiparametric probe sonde and pH_SWS was measured with a Metrohm pH meter (model 780) at SWS scale that was calibrated according to DelValls & Dickson, (1998). · Samples for AT analysis were collected in 500-ml borosilicate bottles, and poisoned with 200 μl of HgCl2-saturated aqueous solution and stored until measurement in the laboratory. AT was measured by potential titration according to Mintrop et al. (2000) with a Titroprocessor (model Metrohm 794 for 2020 and model Metrothm 888 for 2021). · Water samples (5 mL, two replicates) for inorganic nutrients determination were taken, filtered immediately (Whatman GF/F, 0.7 μm) and stored frozen for later analyses in the shore-based laboratory. Nutrients concentrations were measured with a continuous flow auto-analyzer using standard colorimetric techniques (Hansen & Koroleff 1999). · Water samples for DOC and total dissolved nitrogen (TDN) determination were taken, filtered immediately (Whatman GF/F, 0.7 μm) and 100 μl of orthophosphoric acid (3:1) was added. Stored in fridge for later analyses in the laboratory. DOC and TDN concentrations were obtained by catalytic oxidation at high temperature (720°C) and chemiluminescence, respectively, applying the protocol described by Alvarez-Salgado & Miller, (1998). · SSM and the organic (particulate organic matter (POM) and inorganic (particulate inorganic matter (PIM)) fractions were determined by the loss on ignition method, filtering the water through pre-weighed Whatman 0.7 μm GF/F glass fibre filters pre-combusted at 450°C, with subsequent filter desiccation for 48 h and finally combustion. · Chla concentration was obtained by filtering water through Whatman 0.7 μm GF/F glass fibre filters that were maintained frozen and in the dark until analysis. The extract was measured by fluorometry following the method of Welschmeyer (1994)., This work was supported by the European Commission, [Fondo Europeo de Desarrollo Regional (FEDER)] through the project Apoio à gestão das zonas húmidas do litoral do Sudoeste Ibérico: interações entre Aquacultura e meio Ambiente na região transfronteiriça Alentejo-Algarve-Andaluzia 2 (AQUA&AMBI2) [ref: 0750_AQUA_AMBI_2_5_P]. SAV and AR were supported by a pre-doctoral grant from the Spanish Ministry of Science, Innovation and Universities [FPU19/04338 and FPU19/04557]. This work is a contribution to the CSIC Interdisciplinary Thematic Platform OCEANS+., Peer reviewed