Description: A 9-month aquarium experiment with the cold-water Dendrophyllia cornigera was conducted to investigate the single and combined effects of warming, acidification and deoxygenation on its ecophysiological response. The experiment took place at the Aquarium finisterrae (A Coruña, Spain) between 2022-05-06 and 2023-02-24. Treatment values for each parameter (current in situ vs. climate change) were: 12 °C and 15 °C (temperature); ~7.99 and 7.69 (pH); ~8.63 mg/L and 6.45 mg/L (dissolved oxygen concentration). A total of eight treatments (with 3 replicates each, 5 L aquaria) were set up. Concentrations of dissolved nitrates, nitrite, silicate and phosphate were analysed from each experimental aquaria after one, six and nine months. Inorganic nutrient concentrations in seawater were determined using a SFA (Segmented Flow Autoanalyzer) (Aminot & Kérouel, 2007) with a SEAL Analytical QuAAtro analyzer using established colorimetric methods (Hydes et al. 2010 & Becker et al. 2020). RMNs (Reference Material for nutrients in seawater) with different concentration ranges were used for quality control and accuracy of our analysis. Low nutrient seawater (surface seawater filtered and aged) is also used to control low nutrient concentrations.

Description: We used carbon and nitrogen stable isotope (δ13C and δ15N) analyses to investigate the trophic network of the CWC reef habitat off Angola (SE Atlantic Ocean). Samples were collected in January 2016 during the M122 (“ANNA”) expedition on board R/V Meteor. In total, 18 reef sites, including seven CWC mound settings over a bathymetric range of 250 to 530 m water depth, were sampled for stable isotope analyses. Samples of organisms belonging to the taxa Porifera, Cnidaria, Arthropoda, Annelida, Echinodermata and Chordata were collected by means of a box corer, a Van-Veen grab sampler and the Remotely Operated Vehicle (ROV) SQUID (MARUM, Bremen, Germany). To investigate potential food sources of the benthic megafauna, three types of Particulate Organic Matter (POM) were collected: Suspended Particulate Organic Matter (SPOM) was collected with a McLane phytoplankton pump; settling SPOM was collected with a sediment trap (SPOM trap) and sediment samples were collected with a box corer and a grab sampler. Analyses of benthic megafauna were performed using a Elementar IsoPrime 100 isotope ratio–mass spectrometry (IR–MS) (IsoPrime Ltd.) coupled to a CNS elemental analyzer (Elementar Vario Pyro Cube EA CNS; Elementar Analysensysteme GmbH), while POM samples were analyzed by a Delta V Advantage IR–MS coupled online to an elemental analyzer (Flash 2000 EA-IRMS) by a ConFlo IV (Thermo Fisher Scientific Inc.). Vienna Pee Dee belemnite (V.P.D.B.) for carbon, and atmospheric N2 (Air) for nitrogen, were used as reference materials, and stable isotope values are reported in respect to that.

Description: A 9-month aquarium experiment with the cold-water Dendrophyllia cornigera was conducted to investigate the single and combined effects of warming, acidification and deoxygenation on its ecophysiological response. The experiment took place at the Aquarium finisterrae (A Coruña, Spain) between 2022-05-06 and 2023-02-24. Treatment values for each parameter (current in situ vs. climate change) were: 12 °C and 15 °C (temperature); ~7.99 and 7.69 (pH); ~8.63 mg/L and 6.45 mg/L (dissolved oxygen concentration). A total of eight treatments (with 3 replicates each, 5 L aquaria) were set up. Dry mass of the coral nubbins (3 per experimental aquarium) was assessed by means of the buoyant weight technique (Jokiel et al. 1978, Davies, 1989), using an analytical balance (OHAUS AX124, precision 0.1 mg). The dry mass was calculated considering the nubbin net weight in water, the water density and the skeletal density of D. cornigera (2.63 g/cm3; Movilla et al. 2014). Measurements were performed just once the acclimation time finished and after 2 , 4, 6 and 9 months under the experimental conditions. Skeletal growth rates were calculated as the slope of the linear regression between the logarithmically transformed dry mass and the experimental time (%/day) (Orejas et al. 2011).

Description: A 9-month aquarium experiment with the cold-water Dendrophyllia cornigera was conducted to investigate the single and combined effects of warming, acidification and deoxygenation on its ecophysiological response. The experiment took place at the Aquarium finisterrae (A Coruña, Spain) between 2022-05-06 and 2023-02-24. Treatment values for each parameter (current in situ vs. climate change) were: 12 °C and 15 °C (temperature); ~7.99 and 7.69 (pH); ~8.63 mg/L and 6.45 mg/L (dissolved oxygen concentration). A total of eight treatments (with 3 replicates each, 5 L aquaria) were set up. Prokaryotes were quantified by flow citometry (CytoFLEXflex S, Beckman Coulter) as previously described by Gasol et al. (1999) with our own adjustment of the scatter settings to more accurately resolve these cells with the new CytoFLEX flow cytometry technology. Measurements were performed every month from different parts of the aquaria setup: the input seawater, the reservoir tank (after the filtration of seawater to 5 µm and before the UV lamp) and every experimental aquaria.

Description: A 9-month aquarium experiment with the cold-water Dendrophyllia cornigera was conducted to investigate the single and combined effects of warming, acidification and deoxygenation on its ecophysiological response. The experiment took place at the Aquarium finisterrae (A Coruña, Spain), from the 6th of May 2022 to the 24th of February 2023. Treatment values for each parameter (current in situ vs. climate change) were: 12 °C and 15 °C (temperature); ~7.99 and 7.69 (pH); ~8.63 mg/L and 6.45 mg/L (dissolved oxygen concentration). A total of eight treatments (with 3 replicates each, 5 L aquaria) were set up. This dataset contains the registered values for temperature, pH, DO (% air saturation and mg/L) and sainity from the experimental aquarium over the course of the experiment. Temperature and DO were daily measured with a YSI ProODO dissolved oxygen instrument. Salinity was weekly assessed with a WTW 350i multiparameter device equipped with a ConOx probe. Measurements for pH were performed every 1 – 2 months. Samples for pH were directly collected on cylindrical 10 cm cuvettes and analysed on daily basis. After being thermostated at 25ºC, samples were measured using a manual spectrophotometrical procedure with a Sigma Aldrich impure indicator (Clayton and Byrne, 1993). The uncertainty of pH is about 0.005 pH units.

Description: A 9-month aquarium experiment with the cold-water Dendrophyllia cornigera was conducted to investigate the single and combined effects of warming, acidification and deoxygenation on its ecophysiological response. The experiment took place at the Aquarium finisterrae (A Coruña, Spain) between 2022-05-06 and 2023-02-24. Treatment values for each parameter (current in situ vs. climate change) were: 12 °C and 15 °C (temperature); ~7.99 and 7.69 (pH); ~8.63 mg/L and 6.45 mg/L (dissolved oxygen concentration). A total of eight treatments (with 3 replicates each, 5 L aquaria) were set up. Measurements for pH and total alkalinity (TA) were performed on seawater samples from all the experimental aquaria every 1 – 2 months. Samples for pH were directly collected on cylindrical 10 cm cuvettes and analysed on daily basis. After being thermostated at 25ºC, samples were measured using a manual spectrophotometrical procedure with a Sigma Aldrich impure indicator (Clayton and Byrne, 1993). TA was measured following the double end point potentiometric technique by Pérez and Fraga (1987a) and Pérez et al. (2000). Measurements of Certified Reference Material (Dickson's lab, SIO) were performed in order to control the accuracy of the TA measurements. The uncertainty of TA and pH is about 3 μmol/kg and 0.005 pH units, respectively. In situ additional CO2 system variables were calculated using the R package seacarb (Gattuso et al. 2023) using in situ temperature, salinity, measured pH and TA, the dissociation constants of carbonic acid in seawater (K1 and K2) by Lueker et al. (2000), the equilibrium constant of hydrogen fluoride by Perez and Fraga (1987b), the concentration of total boron by Uppström (1974) formulation, and the stability constant of hydrogen sulphate by Dickson (1990). Mean values for the concentration of silicate and phosphate on the aquaria experiments were used in the CO2 calculations, respectively, mean (and standard) deviations as 2.1 (0.4) and 0.31 (0.03) μmol/kg.

Description: A 9-month aquarium experiment with the cold-water Dendrophyllia cornigera was conducted to investigate the single and combined effects of warming, acidification and deoxygenation on its ecophysiological response. The experiment took place at the Aquarium finisterrae (A Coruña, Spain) between 2022-05-06 and 2023-02-24. Treatment values for each parameter (current in situ vs. climate change) were: 12 °C and 15 °C (temperature); ~7.99 and 7.69 (pH); ~8.63 mg/L and 6.45 mg/L (dissolved oxygen concentration). A total of eight treatments (with 3 replicates each, 5 L aquaria) were set up. Raspberry-based controllers were set to modify and monitor the water temperature, pH and dissolved oxygen in every treatment. Values for temperature (ºC), pH (NBS scale) and oxygen (% air saturation) were registered every 15 minutes in a database. The parameters were measured using PT100 temperature sensors, and Atlas Scientific Lab Grade pH and Dissolved Oxygen sensors. Every set of sensors was placed on each header tank, corresponding to each treatment (8 in total). Parameter setpoint values for each header tank were finely adjusted on the controller to ensure the treatment target values on each experimental aquaria. Oxygen sensors from treatments with ambient oxygen (~8.63 mg/L) were removed from the system due to calibration issues. Here, an example of the results for temperature, pH and oxygen for every header tank over 24 hours on 31st of December 2022 is presented. Values for pH (total scale) and dissolved oxygen (mg/L) were calculated using AquaEnv (Hofmann et al. 2010) and respR (Harianto et al. 2019) R packages, respectively, using the in situ temperature and salinity (35.1).

Description: A 9-month aquarium experiment with the cold-water Dendrophyllia cornigera was conducted to investigate the single and combined effects of warming, acidification and deoxygenation on its ecophysiological response. The experiment took place at the Aquarium finisterrae (A Coruña, Spain) between 2022-05-06 and 2023-02-24. Treatment values for each parameter (current in situ vs. climate change) were: 12 °C and 15 °C (temperature); ~7.99 and 7.69 (pH); ~8.63 mg/L and 6.45 mg/L (dissolved oxygen concentration). A total of eight treatments (with 3 replicates each, 5 L aquaria) were set up. Respiration rates from each nubbin (3 per aquarium) were assessed after 6 and 9 months under the experimental conditions by means of closed-cell incubations. Oxygen consumption was calculated by measuring the dissolved oxygen concentration of the seawater inside the chamber using an optical oxygen sensor (YSI ProODO) at the beginning and at the end of the incubation time (24 h incubation). Dry mass (g) of the coral nubbins was assessed by means of the buoyant weight technique (Jokiel et al. 1978, Davies, 1989), using an analytical balance (OHAUS AX124, precision 0.1 mg). Tissue surface area (cm2) was assessed on virtual 3D models of each nubbin at the time when the measurements were conducted. Respiration rates were normalised by dry mass and by tissue surface area.

Description: Water column raw data using the ship's own Kongsberg EM 122 multibeam echosounder was not continuously recorded during RV METEOR cruise M122. Data was recorded on 10 days between 2015-12-31 and 2016-01-27. The data are archived at the Federal Maritime and Hydrographic Agency of Germany (Bundesamt für Seeschifffahrt und Hydrographie, BSH) and provided to PANGAEA database for data curation and publication. Ancillary sound velocity profiles (SVP) files from the cruise are archived at the BSH and added to the corresponding multibeam raw dataset https://doi.org/10.1594/PANGAEA.945013 This publication is conducted within the efforts of the German Marine Research Alliance in the core area 'Data management and Digitalization' (Deutsche Allianz Meeresforschung, DAM).

Description: Multibeam bathymetry raw data using the ship's own Kongsberg EM 710 multibeam echosounder was almost continuously recorded during RV METEOR cruise M122. Data was recorded on 25 days between 2015-12-30 and 2016-01-23. This dataset contains a survey towards the coast of Namibia & Angola. The approximate average depth of the entire dataset is around 400m. The data are archived at the Federal Maritime and Hydrographic Agency of Germany (Bundesamt fÃür Seeschifffahrt und Hydrographie, BSH) and provided to PANGAEA database for data curation and publication. Ancillary sound velocity profiles (SVP) files from the cruise are archived at the BSH, thus SVP files are added to this dataset. Also data analysis of the multibeam raw data revealed that SVP has been changed during the survey. This publication is conducted within the efforts of the German Marine Research Alliance in the core area 'Data management and Digitalization' (Deutsche Allianz Meeresforschung, DAM) Data are unprocessed and therefore contains incorrect depth measurements (artifacts) without further processing. Note that refraction errors can be expected due to the lack of proper SVP. Overall, it appears that the data quality is rather good since the gridded hillshade data showed relatively few obstacles. Data acquisition has been monitored at all times during surveying. Data can be processed e.g. with the open source software package MB-System (Caress, D. W., and D. N. Chayes, MB-System: Mapping the Seafloor, http://www.mbari.org/products/research-software/mb-system/, 2022).