ALBERT

Description: In the Peruvian upwelling area, benthic biogeochemical fieldwork focused on the FS Meteor cruises M77/1, M77/2, M92, M136, and M137. Off Mauritania, benthic investigations were mainly conducted on FS Maria S. Merian cruise MSM17/4 and FS Meteor cruise M107 (Sommer et al., 2021; see Table 2 and supplementary Tables S29 to S35). Research questions addressed organic carbon degradation, associated element cycling, and solute fluxes in the benthic boundary layer in response to variable bottom water redox conditions and hydrodynamic forcing (e.g. Bohlen et al., 2011; Dale et al., 2014; Dale et al., 2016; Dale et al., 2019; Dale et al., 2021; Loginova et al., 2020; Lomnitz et al., 2016; Noffke et al., 2012; Plass et al., 2020; Schroller-Lomnitz et al., 2019; Sommer et al., 2016). Effects of variable bottom water conditions on seabed nutrient and trace metal release were studied during in situ and ex situ on-board sediment incubations and the analysis of pore water geochemistry. Further emphasis was placed on resolving the imprint of specific microbial processes and foraminiferal metabolic activity on element turnover and exchange across the sediment water interface (e.g. Glock et al., 2013, 2019, 2020; Gier et al., 2016, 2017; Scholz et al., 2016; 2017). The results were further interpreted using benthic numerical models (e.g. Bohlen et al., 2011; Dale et al., 2014, 2015, 2016, 2017, 2019).

Description: LADCP measurements were performed on all research cruises that concentrated on open ocean areas (see Table C3) while on cruises that worked mostly in shallow waters, ocean current measurements by the shipboard ADCP (see section 4.1.8) were deemed sufficient. GEOMAR used a two-instrument configuration with two Teledyne RDI 300 kHz workhorse ADCPs mounted in down- and up-looking positions. Data collection and processing was performed according to recommendations in the GO-SHIP manual (Thurnherr et al., 2010).

Description: Ocean turbulence measurement programs were carried out during 22 cruises to quantify the dissipation rate of turbulent kinetic energy and infer rates of turbulent mixing (see Table C6). The used shipboard microstructure profiling systems 165 (MSS) were manufactured by Sea & Sun Technology and consisted of a profiler (MSS90-D, S/N 26, 32 and 73), a winch having 500-1000 m of cable and a data interface. All profilers were equipped with three microstructure shear sensors, a fast- response temperature sensor (PF07), an acceleration sensor and two tilt sensors as well as conductivity (Sea & Sun Tech.), temperature (Sea & Sun Tech.), pressure (Keller), turbidity (Seapoint) and oxygen sensors sampling with a lower response time. The profilers were optimized to sink at a rate of 0.5-0.6 m s-1. Standard processing procedures were used to determine 170 the rate of kinetic energy dissipation of turbulence in the water column (see Schafstall et al. (2010) for a detailed description). Additionally, during several autonomous glider missions, a microstructure probe was mounted to the top of the gliders. These probes (MicroRider) were manufactured by Rockland Scientific and carried two microstructure shear and temperature sensors as well as pressure, accelerometer and tilt sensors. The data processing is detailed in Foltz et al. (2020).

Description: CTDO measurements were acquired on the major research cruises performed as part of the SFB 754 or other projects . Seabird 911plus systems equipped with dual temperature-conductivity-oxygen sensors were employed. All systems had a 24-bottle water sampling rosette with 10 l Niskin bottles. On some cruises only 22 bottles were mounted to accommodate a lowered Acoustic Doppler Current Profiler for deep ocean current observations. Water sampling, processing, and calibration followed GO-SHIP recommendations (Swift, 2010; McTaggart et al., 2010; Uchida et al., 2010) and included the recommended steps Data Conversion, Sensor Time-Alignment, Creation of Bottle Files, Outlier Removal, Pressure Sensor Filtering, Conductivity Cell Thermal Mass Correction, Ship Roll Correction and Deck Offset Correction by Loop Editing, as well as Derivation of Calculated Properties. After these steps, conductivity and oxygen readings were calibrated against values determined with salinometry and Winkler titration , respectively. Finally, the downcast data was averaged over 1 dbar wide intervals. An independent upcast calibration was used to obtain calibrated CTDO values coincident with the discrete water samples.

Description: During the second funding phase (2012-2015) a new CTD system became available that could be deployed from a moving 185 ship. First a Teledyne Oceanscience UCTD and later a Teledyne Oceanscience Rapidcast system were acquired and deployed successfully on several cruises (see Table C8). They allowed for the sampling of water masses at high horizontal resolution (ranging from less than 1 km for the Rapidcast system to 10 km for deep UCTD casts) with good accuracy of the pressure, temperature, and conductivity sensors. Processing of the data involved mostly the fall-rate dependent correction of the thermal lag of the conductivity sensor and followed the approach described by Ullman and David (2014). Subsequently 190 the corrected data was calibrated against the calibrated coincident Thermosalinograph and the calibrated nearby CTD data. The typical accuracies of the final pressure, temperature, and salinity data are 1 dbar, 0.01 °C, and 0.01 g/kg, respectively.

Description: The SFB 754 also made a contribution to the global ARGO float program. In 2009, 2911, and 2014 several floats equipped with additional Aanderaa oxygen sensors were deployed off Peru to study the effects of mesoscale eddies on the flow field 200 and the water masses (see Table C10; Czeschel et al., 2018). A number of floats was deployed in the tropical Atlantic to accompany a tracer release experiment (see section 4.2.3). Additionally several of the cruises were used to deploy regular ARGO floats on behalf of the German Hydrographic Office.

Description: lmost all long-term moored observations of the SFB 754 were conducted in the tropical Atlantic between the equator and 18° N, except for one mooring that was deployed in the tropical South Pacific (see Table C4). Moorings were typically equipped with instruments recording pressure, temperature, conductivity, dissolved oxygen and current velocity. The moorings at 17.6° N, 24.2° W which have been deployed in the same location for several periods were additionally equipped with biogeochemical sensors recording variables such as partial pressure of CO2 (pCO2), fluorescence, and particle fluxes. Instruments with pressure, temperature, conductivity and oxygen sensors were calibrated in situ immediately prior to and after a mooring deployment period by attaching them to the CTD frame during CTDO casts. Correction terms were then developed from the difference between the sensor readings and the calibrated CTDO data during several minute long calibration stops. These correction terms were then applied to the full deployment periods. This ensured best data quality with recognition of potential sensor drifts and also allowed for the estimation of calibration and measurement errors (Hahn et al. 2014, Bittig et al. 2018, Berx et al. 2019). Moored Acoustic Doppler Current Profiler bin depths were corrected using the sound speed at instrument depth following the approach by Shcherbina et al. (2005). Velocities were not corrected, but respective measurement errors were assumed as described in Hahn et al. (2014). For all instruments within a mooring that did not record pressure, full deployment pressure time series were estimated by linearly interpolating between the instruments having a pressure sensor.

Description: Nutrient, transient tracer and N2O water column measurements

Description: Continuous measurements of the climate-relevant trace gases carbon dioxide (CO2), nitrous oxide (N2O), and carbon monoxide (CO) in the surface ocean and overlying atmosphere were conducted during 9 SFB 754 cruises (see Table C14) spanning the North, South and equatorial Atlantic, as well as the South and equatorial Pacific. To this end, laser spectroscopy-based gas analyzers coupled to air-water equilibration chambers were used. For details of the analytical systems the reader is referred to the descriptions provided by Arévalo-Martínez et al. (2013) and Arévalo-Martínez et al. (2019). All trace gas measurements were quality-controlled to achieve the international standards for marine CO2 (Bender et al., 2002), N2O (Bange et al., 2019), and atmospheric CO (Zellweger et al., 2019; to date there is no accepted standard for seawater measurements). The final quality-controlled data is available through the Surface Ocean CO2 Atlas (SOCAT, https://www.socat.info/) and the Marine CH4-N2O database (MEMENTO, https://memento.geomar.de/) as well as on Pangaea

Description: Particulate organic matter (POM) distribution in the water column as on several cruises determined after filtration onto pre-combusted, acid-washed GF/F filters (Franz et al., 2012a). Particulate organic phosphorus (POP) collected on GF/F filters was determined colorimetrically. Samples for phytoplankton pigment concentrations were collected by filtration of seawater from the CTD/rosette through GF/F filters, and stored at -80°C immediately after filtration. Transparent exopolymer particles (TEP) and Coomassie stainable particles were filtered under low pressure (〈 150 mbar) onto 25 mm Nuclepore membrane filters (0.4 μm pore size, Whatman Ltd.) and stained with Alcian Blue and Coomassie Brilliant Blue, respectively. Export flux of was characterized using surface-tethered sediment traps (Engel et al., 2017), with Particle Interceptor-Traps (PIT) following Knauer et al. (1979).

Description: Dissolved Organic Matter, Cell Abundance and Extracellular Enzyme Rates and Bacterial Production from several cruises and experiments from 2008-2018

Description: A Hydrobios Multinet Midi with an aperture of 0.25 m2 and 5 nets (mesh size 200 μm) was deployed for vertically stratified hauls on several cruises, mostly in paired day-night hauls to quantify diel vertical migration. Standard depths used for these deployments were 1000-600-300-200-100-0 m. On M93, a Multinet Maxi (9 nets, 333 μm mesh) was used instead. Samples were fixated in 4% formaldehyde in seawater solution, scanned at GEOMAR or at OSCM, and analyzed using automated imaging software (Gorsky et al., 2010) allowing taxonomical classification as well as the estimation of taxon-specific biomass (Lehette and Hernandez-Leon, 2006) and metabolic rates.

Description: To expand the ecological knowledge on fragile organisms (such as giant rhizaria, medusae, ctenophores, and siphonophores) in situ imaging techniques were employed in addition to net sampling. An Underwater Vision Profiler 5 (UVP5; Picheral et al., 2010) was routinely mounted on the CTD/rosette during most SFB 754 cruises since 2012. During the cruises in 2012 and 2013 a UVP5 was used that was kindly provided by the Laboratoire d'Océangraphie de Villefranche-sur-Mer. The instrument consists of one down facing HD camera in a steel pressure case and two red LED lights which illuminate a 0.88 to 0.93 l volume (depending on the actual set-up). During the downcast, the UVP5 takes 3-20 pictures of the illuminated field per second. For each picture, the particles are counted and sized immediately and the data is stored in the instrument for later analysis.

Description: Zooplankton metabolic rates (oxygen respiration and ammonium excretion) at different temperatures, oxygen, and carbon dioxide partial pressures (Kiko et al., 2015; 2016) were measured during three cruises. Zooplankton was collected by different nets and the entire catch immediately transferred to 10 l beakers containing pre-cooled seawater. Diel vertical migrators were sampled at the surface at night. Individuals for respiration rate measurements were isolated immediately and maintained in filtered seawater for 1 to 13 hours at the chosen experimental temperature (13, 18 or 23°C). Only animals appearing unharmed and fit were used for experiments. Water for the respiration and excretion rate trials was UV-treated, filtered over a 0.2 µm sterile filter, and supplemented with antibiotics (25 mg l-1 ampicillin and 25 mg l-1 streptomycin). Subsequently, the water was bubbled with different Gas mixtures (N2, O2, CO2, see Kiko et al., 2016 for details) adjusted to the chosen pO2 and pCO2 levels.

Description: One of the objectives of the SFB 754 was the reconstruction of the factors controlling the intensity and the spatial extent of the OMZ in the Eastern Tropical Pacific, specifically off Peru, since the Last Glacial Maximum (21000 years ago). For the purpose of these paleoceanographic studies, long gravity cores were recovered during four scientific expeditions (M77/1, M77/2, M92, and M135; see Figure 4). During the cruises M77/1 and M77/2 in 2008, 51 sediment cores were retrieved below and in the centre of the OMZ, from ~17° S to the equator (Pfannkuche et al., 2011; see Figure 4). Most of the records collected in the core of the OMZ (i.e. ~200 to ~500 m depth), from ~8 to 15° S, show sedimentary discontinuities during the Holocene (last 11700 years), which preclude high resolution paleoceanographic reconstructions in this area (Erdem et al., 2016; Salvatteci et al., 2014, 2016). Based on the information collected during M77/1 and M77/2 and also on the scientific literature, cruise M135 aimed specifically at finding the most complete Holocene sequence in the Eastern Tropical South Pacific. For this purpose, a detailed paleoceanographic survey took place at ~17° S, an area that is less affected by processes that can produce sediment discontinuities. Six sediment cores were retrieved, two of which contained the most complete sediment sequences for the last 10 000 years (Salvatteci et al., 2019).

Description: One of the objectives of the SFB 754 was the reconstruction of the factors controlling the intensity and the spatial extent of the OMZ in the Eastern Tropical Pacific, specifically off Peru, since the Last Glacial Maximum (21000 years ago). For the purpose of these paleoceanographic studies, long gravity cores were recovered during four scientific expeditions (M77/1, M77/2, M92, and M135; see Figure 4). During the cruises M77/1 and M77/2 in 2008, 51 sediment cores were retrieved below and in the centre of the OMZ, from ~17° S to the equator (Pfannkuche et al., 2011; see Figure 4). Most of the records collected in the core of the OMZ (i.e. ~200 to ~500 m depth), from ~8 to 15° S, show sedimentary discontinuities during the Holocene (last 11700 years), which preclude high resolution paleoceanographic reconstructions in this area (Erdem et al., 2016; Salvatteci et al., 2014, 2016). Based on the information collected during M77/1 and M77/2 and also on the scientific literature, cruise M135 aimed specifically at finding the most complete Holocene sequence in the Eastern Tropical South Pacific. For this purpose, a detailed paleoceanographic survey took place at ~17° S, an area that is less affected by processes that can produce sediment discontinuities. Six sediment cores were retrieved, two of which contained the most complete sediment sequences for the last 10 000 years (Salvatteci et al., 2019).

Description: One of the objectives of the SFB 754 was the reconstruction of the factors controlling the intensity and the spatial extent of the OMZ in the Eastern Tropical Pacific, specifically off Peru, since the Last Glacial Maximum (21000 years ago). For the purpose of these paleoceanographic studies, long gravity cores were recovered during four scientific expeditions (M77/1, M77/2, M92, and M135; see Figure 4). During the cruises M77/1 and M77/2 in 2008, 51 sediment cores were retrieved below and in the centre of the OMZ, from ~17° S to the equator (Pfannkuche et al., 2011; see Figure 4). Most of the records collected in the core of the OMZ (i.e. ~200 to ~500 m depth), from ~8 to 15° S, show sedimentary discontinuities during the Holocene (last 11700 years), which preclude high resolution paleoceanographic reconstructions in this area (Erdem et al., 2016; Salvatteci et al., 2014, 2016). Based on the information collected during M77/1 and M77/2 and also on the scientific literature, cruise M135 aimed specifically at finding the most complete Holocene sequence in the Eastern Tropical South Pacific. For this purpose, a detailed paleoceanographic survey took place at ~17° S, an area that is less affected by processes that can produce sediment discontinuities. Six sediment cores were retrieved, two of which contained the most complete sediment sequences for the last 10 000 years (Salvatteci et al., 2019). In addition, core tops of near sediment surface cores from multi-corers (MUCs) have been used to establish local calibrations for several paleoproxies, such as redox-sensitive elements in foraminifera (i.e. Mn/Ca, I/Ca and Fe/Ca), foraminiferal assemblages, and stable Mo and N isotopes

Description: Trace metal clean sampling equipment was deployed on a sub-set of cruises to facilitate the observation of contamination prone chemical parameters. All trace metal sample collection, handling, and analysis was conducted in accordance with GEOTRACES protocols which have been updated through the SFB754 program (Cutter et al., 2014). For cruises with extensive trace metal work, the deployment of an over-pressured clean container on deck facilitated sampling and collection of trace metal and other contamination-prone samples at sea. For cruises from 2008 to 2013, PTFE-coated 8 l GO-FLO bottles (General Oceanics) were mounted on a Kevlar wire with sample handling and preservation as per Chever et al. (2015). From 2014 onwards, 24 Ocean Test Equipment (OTE) samplers were deployed mounted on a powder coated sampling CTD (Sea-Bird SBE25) rosette using a Kevlar conducting cable with sample handling and preservation as per Rapp et al. (2019).

Description: Seawater samples for stable isotopes measurements of dissolved silicate (δ30Si), nitrate (δ15NO3-) and nitrite (δ15NO2-) were taken from the CTD/rosette on a number of SFB 754 cruises. Seawater samples for Rare Earth Element (REE) concentrations and neodymium (Nd) isotopes were taken during M77/3, M77/4 (Grasse et al., 2012) and during M90 in the Panama Basin (Grasse et al., 2017).

Description: SADCP data were acquired on 33 of the research cruises On FS Meteor, FS Maria S. Merian and FS Sonne II two Teledyne RDI Ocean Surveyor systems with 38 and 75 kHz transmission frequency were used, while on NO l'Atalante a single 75 kHz system was used. All data was processed with a software package developed at GEOMAR following the GO-SHIP standards (Firing and Hummon, 2010). The data was subsequently averaged over one minute intervals, converted to a NetCDF based format and published. For a small number of cruises, the signal strength information of the SADCP data has also been used to estimate the backscatter in the ocean. These data sets were processed following Mullinson (2017) and published separately from the regular SADCP data (see also Table C7).

Description: For 32 SFB 754 cruises near surface temperatures and salinities were collected using the ships' thermosalinograph systems. The four ships on which the major cruises were conducted were equipped with different systems with either one or two 195 thermosalinographs in parallel or in alternating operating mode (see Table C9). All TSG data were cross-calibrated against the calibrated CTD data at the depth of the seawater intake for the TSG systems.

Description: Bioassays with amendment of DIN, DIP, and various trace elements were conducted in short-term replicated bottle incubations to determine limiting elements for phytoplankton growth (Browning et al., 2017). Shipboard mesocosm experiments with a duration from 7 to 11 days were conducted on several cruises in the ETNA and ETSP and land-based on Cape Verde to determine the impact of N:P stoichiometry on the pelagic community (Franz et al., 2012b; Hauss et al., 2012; Meyer et al., 2016) and dissolved organic compounds (Loginova et al., 2015; Engel et al., 2015).

Description: Autonomous gliders were deployed during several cruises but also as stand-alone missions independent from large research vessels (see Table C5). Two different generations of Teledyne Webb Research Slocum gliders were used, G1 and G2. All gliders were equipped with Seabird CTD systems, G1 gliders with an unpumped and G2 gliders with a pumped version, respectively. An Aanderaa optode was present on all gliders to observe dissolved oxygen concentrations. Optical fluorescence and backscatter sensors manufactured by Wetlabs were also present on all gliders albeit in different configurations. They allowed the determination of CHL-a (excitation and emission wavelengths of 470 and 695 nm, respectively) and CDOM (excitation and emission wavelengths of 370 and 460 nm, respectively) concentrations and the turbidity (scattering wavelength of 470 nm) of the waters. All glider data was processed using a GEOMAR-developed software (Thomsen et al., 2016) resulting in gridded fields for all observed variables. During a small number of glider deployments, a Seabird/Satlantic SUNA Nitrate sensor was attached to a glider. SUNA data was again processed following the procedures outlined in Sakamoto et al. (2009) and Sakamoto et al. (2017) and calibrated against Nitrate measurements from nearby CTDO casts with discrete Nitrate measurements. Microstructure sensors were also attached to gliders on several deployments (see the following section).

Description: Dinitrogen (N2) and carbon (C) fixation rates were measured on 9 cruises (see Table C17) using shipboard incubation experiments, complemented with nutrient and oxygen manipulations. During cruises M77/3, M77/4 and M80/2, N2 fixation was measured using the bubble addition method following Montoya et al (1996). During M80/2 a novel method based on 360 15N2 gas pre-dissolution, which was developed by Mohr et al. (2010), was tested in parallel to the classic method. An underestimation of N2 fixation rates by the classic method has been observed (Großkopf et al., 2012) and therefore the novel 'pre-dissolution method' was applied during the following cruises (M83/1, M90, M91, M93, M97, M104, M107). Single cell N2 fixation rates to differentiate the contribution of different clades of N2 fixers were measured using a NanoSIMS (Martinez-Perez et al., 2016).

Description: Potential rates for microaerobic respiration and aerobic organic matter degradation as a source of ammonia (NH4+) in the Peruvian OMZ was assessed using an 18O2 labelling approach suitable for microaerobic respiration (Holtappels et al., 2014). Further, the effects of O2 depletion associated with marine snow particles on microbial respiration was explored by combining 18O2 labelling experiments with in-situ particle size analysis and modelling of aggregate-size dependent respiration (Kalvelage et al., 2015). Anammox, denitrification, and nitrification, as well as N2O production rates were measured on several cruises (Kalvelage et al., 2011; Löscher et al., 2012; Callbeck et al., 2017; Bourbonnais et al., 2017; Frey et al., 2020) using isotope fractionation studies, 15N tracer additions, and inhibitor studies.

Description: One of the objectives of the SFB 754 was the reconstruction of the factors controlling the intensity and the spatial extent of the OMZ in the Eastern Tropical Pacific, specifically off Peru, since the Last Glacial Maximum (21000 years ago). For the purpose of these paleoceanographic studies, long gravity cores were recovered during four scientific expeditions (M77/1, M77/2, M92, and M135; see Figure 4). During the cruises M77/1 and M77/2 in 2008, 51 sediment cores were retrieved below and in the centre of the OMZ, from ~17° S to the equator (Pfannkuche et al., 2011; see Figure 4). Most of the records collected in the core of the OMZ (i.e. ~200 to ~500 m depth), from ~8 to 15° S, show sedimentary discontinuities during the Holocene (last 11700 years), which preclude high resolution paleoceanographic reconstructions in this area (Erdem et al., 2016; Salvatteci et al., 2014, 2016). Based on the information collected during M77/1 and M77/2 and also on the scientific literature, cruise M135 aimed specifically at finding the most complete Holocene sequence in the Eastern Tropical South Pacific. For this purpose, a detailed paleoceanographic survey took place at ~17° S, an area that is less affected by processes that can produce sediment discontinuities. Six sediment cores were retrieved, two of which contained the most complete sediment sequences for the last 10 000 years (Salvatteci et al., 2019).