ALBERT

Description: Particle number size distributions (PNSD) in the mobility diameter range of 10 nm to 800 nm were measured using a Mobility Particle Size Spectrometer (MPSS, TROPOS-built; Wiedensohler et al., 2012). During HALO–(AC)³, the MPSS was situated in the aerosol rack (with a compact filter sampler and a miniature CCN counter) onboard Polar 6 and permanently connected to the standard aerosol inlet (Leaitch et al., 2016). Near isokinetic sampling was established for the majority of the flight time by restricting the total aerosol flow through the sampling line (outer diameter 0.75 inch) with the help of a valve. With this, an upper cut-off diameter of roughly 4 µm could be achieved. Each scan of the entire particle size range took approximately 5 min. Data are provided as bin-wise log-normal particle number (dN/dlogDp) for P6 RF01–13. For each of the 40 size bins, the bin's midpoint diameter (Dp) is given. The start and end of each scan is given. Each PNSD was integrated over all Dp to obtain the total particle number concentration (Ntotal). A data flag is given to indicate when sampling was under near-isokinetic conditions. For each scan, the given geolocation is the centroid of P6's flighttrack within the scan's duration. Analogous, the given altitude is the mean altitude of P6 over each scan's duration. All concentration values have been corrected to standard conditions (1013.0 hPa and 273.15 K).

Description: This data contains monitoring data of the RV ALKOR cruise AL606 conducted in January 2024 (January 22nd – January 20th) in the Western Baltic Sea by the University of Hamburg. The cruise was part of the 5-year monitoring programme Winter cod 2021-25 (Monitoring winter spawning activity of Western Baltic cod (Gadus morhua) (2021-25)) of the University of Hamburg aiming at investigating the early-winter spawning activity of Western Baltic cod to identify potential climate-induced shifts in spawning phenology. The data set includes station data (i.e. action log) of the cruise.

Description: We investigated seawater microbial abundance, activity and diversity throughthree laboratory-controlled bottle incubations mimicking different mixing scenarios between SGD (either ambient or filtered through 0.1 µm/0.22 µm) and seawater to determine the contribution of SGD to the coastal microbial community. The experiments were conducted with five different treatments (including ambient seawater not exposed to SGD) in triplicates. The first experiment (Exp. 1) was designed to test the relative contribution of brackish discharged groundwater (salinity = 7.9 ppt vs. the ambient salinity of the SEMS of ~39.5 ppt) on the microbial productivity and abundance of reference coastal seawater by mixing different ratios (1, 5, 10 and 20% v:v) of discharged groundwater. Discharged groundwater was collected into acid-cleaned containers on the day the experiment was initiated near Achziv Nature Reserve (33° 3′52 N, 35° 6′14.94 E). The second and third experiments (Exp. 2; Exp.3) were designed to extend Exp. 1 and aimed to specifically investigate how groundwater-derived microorganisms affect the activity and abundance of marine organisms once discharged into the sea. For these experiments, fresh groundwater (FGW) was collected from drilling wells and pumped into 20 L acid-cleaned sample-rinsed carboys the same day the experiment was initiated. At the laboratory, fresh groundwater was either filtered through a 0.1 μm polycarbonate filter (Exp. 2) or serially filtered through 0.22 and 0.1 μm polycarbonate filter (Exp. 3) and the filtrate was added to seawater in different mixing scenarios. Ambient coastal seawater was collected by pumping at the Israel Oceanographic and Limnological Research Institute (IOLR) into acid-cleaned carboys, and mixed with either brackish groundwater (Exp.1) or fresh groundwater (Exp. 2, Exp. 3) at the desired ratios and filtration size. The duration of the experiments was 3-5 days, and samples were taken for the following analyses: chlorophyll a (Exp. 1 & 2, every 24Hr.), dissolved nutrient concentrations (Exp. 2 & 3 T zero and T final), flow cytometry (bacterial and phytoplankton abundance, every 24Hr.), primary and heterotrophic production rates (Exp. 1 & 2, every 24Hr.; Exp. 3 T zero and T final). Currently, little is known about the interactions between groundwater-borne and coastal seawater microbial populations, and groundwater microbes' role upon introduction to coastal seawater populations. Here, we investigated seawater microbial abundance, activity and diversity through laboratory-controlled bottle incubations mimicking different mixing scenarios between SGD (either ambient or filtered through 0.1 µm/0.22 µm) and seawater.

Description: A gas inlet was installed at the bow of RV Poseidon. Atmospheric gas concentrations of CH4 and CO2 were measured continuously with a Picarro G2301-f analyzer.

Description: This study estimated the short-term decomposition effects of the invasive jellyfish Rhopilema nomadica on nutrient dynamics at the sediment-water interface in the Eastern Mediterranean Sea using core incubations. The degradation of R. nomadica has led to increased oxygen demand and acidification of overlying water as well as high rates of dissolved organic nitrogen and phosphate production.

Description: We investigated seawater microbial abundance, activity and diversity in a site strongly influenced by submarine groundwater discharge (SGD). We combined in-situ observations and laboratory-controlled bottle incubations mimicking different mixing scenarios between SGD (either ambient or filtered through 0.1 µm/0.22 µm) and seawater. Three sampling campaigns (August 2020, February 2021 and July 2021) were conducted at a field site, highly influenced by SGD (Achziv, northern Israel), which we recently compared to a reference site (Shikmona) at the oligotrophic Israeli shallow rocky coast. Each field campaign lasted 2-5 days and covered at least 2 tidal cycles. Porewater samples were collected on the shoreline using piezometers (AMS piezometers that reach depths of 〈2 meters) and a portable peristaltic pump. The density (g cm-3), electric conductivity (mS/cm), temperature (°C) and pH, of surface seawater, porewater and groundwater were measured on-site at the time of the sampling. Samples for microbial analysis were collected from the piezometers and divided to aliquots: 1. For community analysis, samples were immediately filtered through polycarbonate 0.2 μm pore size filters, which were kept on ice and transported to the laboratory on the same day. Filter samples were stored frozen (-20°C) until DNA extraction (filtered porewater were kept for dissolved nutrient measurements. After thawing, each filter was cut into small pieces using a sterile scalpel blade, which was placed immediately into PowerSoil DNA bead tubes and extracted with the dNeasy PowerSoil Kit (Qiagen, USA) following the standard protocol. To generate 16S rRNA gene libraries, the V3–V4 hypervariable region of the 16S gene was amplified and sequenced on the Illumina MiSeq platform. Quality-filtered reads were imported into QIIME 2 platform, denoised, dereplicated, clustered and trimmed using the DADA2 plugin. Taxonomic assignment of the ASVs was achieved against the Silva database. The ASV table is provided under "additional metadata". Raw data from Illumina MiSeq sequencing are deposited to the National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA) under BioProject number PRJNA973031 (will be available upon publication). 2. For Pico-/nano-phytoplankton and heterotrophic prokaryotic abundance, non-filtered samples were chilled on ice and transported to the laboratory on the same day. Samples (1.8 mL) were fixed with glutaraldehyde (final concentration 0.02 % v:v, Sigma-Aldrich 253 G7651), frozen in liquid nitrogen, and later stored at −80°C until analysis. The abundance of autotrophic pico- and nano-eukaryotes, Synechococcus and Prochlorococcus, and other heterotrophic prokaryotes (bacteria and archaea) was determined using an Attune® Acoustic Focusing Flow Cytometer (Applied Biosystems) equipped with a syringe based fluidic system and 488 and 405 nm lasers. To measure heterotrophic prokaryote abundance, a sample aliquot was stained with SYBR Green (Applied Biosystems). 3. Prokaryotic (bacteria and archaea) heterotrophic production was estimated using the 3H-leucine incorporation method. Photosynthetic carbon fixation rates were estimated using the 14C incorporation method.

Description: This data contains monitoring data of the RV ALKOR cruise AL607 conducted in February 2024 (February 10th – February 16th) in the Western Baltic Sea by the University of Hamburg. Sampling activities conducted during this teaching cruise was part of the international sampling efforts to investigate the spawning activity of Western Baltic cod (Gadus morhua) coordinated by the Western Baltic cod Forum (WBCF). The data set includes station data (i.e. action log) of the cruise.

Description: This data contains monitoring data of the RV ALKOR cruise AL607 conducted in February 2024 (February 10th – February 16th) in the Western Baltic Sea by the University of Hamburg. Sampling activities conducted during this teaching cruise was part of the international sampling efforts to investigate the spawning activity of Western Baltic cod (Gadus morhua) coordinated by the Western Baltic cod Forum (WBCF). The data set includes cod single fish analysis data. All single fish measurements were made directly on board. Full wet weights of cod were measured and subsequently cod were gutted and liver weights, gonad weights and sexes, gutted wet weights (i.e., gutted wet mass), gonad stages and liver nematode infestations were recorded, and Otoliths were taken.

Description: We investigated seawater microbial abundance, activity and diversity in a site strongly influenced by submarine groundwater discharge (SGD). Three sampling campaigns (August 2020, February 2021 and July 2021) were conducted at a field site, highly influenced by SGD (Achziv, northern Israel), Each field campaign lasted 2-5 days and covered at least 2 tidal cycles. Pore-water samples were collected on the shoreline using piezometers (AMS piezometers that reach depths of 〈2 meters) and a portable peristaltic pump. The density (g cm-3), electric conductivity (mS/cm), temperature (°C) and pH, of surface seawater, porewater and groundwater were measured on-site at the time of the sampling. Samples for microbial analysis were collected from the piezometers and divided to aliquots: 1. For community analysis, samples were immediately filtered through polycarbonate 0.2 μm pore size filters, which were kept on ice and transported to the laboratory on the same day. Filter samples were stored frozen (-20°C) until DNA extraction (filtered pore-water were kept for dissolved nutrient measurements. After thawing, each filter was cut into small pieces using a sterile scalpel blade, which was placed immediately into PowerSoil DNA bead tubes and extracted with the dNeasy PowerSoil Kit (Qiagen, USA) following the standard protocol. 2. For Pico-/nano-phytoplankton and heterotrophic prokaryotic abundance, non-filtered samples were chilled on ice and transported to the laboratory on the same day. Samples (1.8 mL) were fixed with glutaraldehyde (final concentration 0.02 % v:v, Sigma-Aldrich 253 G7651), frozen in liquid nitrogen, and later stored at −80°C until analysis. The abundance of autotrophic pico- and nano-eukaryotes, Synechococcus and Prochlorococcus, and other heterotrophic prokaryotes (bacteria and archaea) was determined using an Attune® Acoustic Focusing Flow Cytometer (Applied Biosystems) equipped with a syringe based fluidic system and 488 and 405 nm lasers. To measure heterotrophic prokaryote abundance, a sample aliquot was stained with SYBR Green (Applied Biosystems). 3. Prokaryotic (bacteria and archaea) heterotrophic production was estimated using the 3H-leucine incorporation method. Photosynthetic carbon fixation rates were estimated using the 14C incorporation method.

Description: Sample C1W originates from Sula reef, off Norway, where it was taken with the submersible Jago during Poseidon cruise POS455 (position: 64.1110°N, 8.1187°E, 303 m water depth; white colourmorp. The coral colony fragment was scanned by a Toshiba Aquilion 64 computer tomograph (CT) at the hospital Klinikum Bremen-Mitte with an x-ray source voltage of 120 kV and a current of 600 mA. The CT image stack has a resolution of 0.35 mm in x-direction and y-direction and 0.5 mm resolution in z-direction (0.3 mm reconstruction unit). Images were reconstructed using Toshiba's patented helical cone beam reconstruction technique (TCOT) and are provided in DICOM-format. Polyp-cavity (calice) segmentation was perfromed with the ZIB edition of the Amira software (Stalling et al., 2005; http://amira.zib.de) based on the new method describes in Schmitt et al. (submitted).

Description: Sample SaM-ID43148 was retrieved during Meteor cruise M70-1 with the ROV MARUM-Quest from the Gondola Slide, southeast of the Gargano Promontory in the Adriatic Sea (Station M70/1-752, GeoB11207, 41°43.51'N, 17°02.78'E, 710 m water depth). The specimen was scanned with a Philips Brilliance iCT Elite 256 computer tomograph (x-ray source, voltage: 120 kV; current: 300 mA; physical resolution: 0.313 in xy-direction, respectively, 0.625 mm in z-direction; re-construction interval in z-direction: 0.3 mm; reconstruction: filtered Back Projection (fBP) mode and a bone kernel (YB (Enhanced)). Polyp-cavity (calice) segmentation was perfromed with the ZIB edition of the Amira software (Stalling et al., 2005; http://amira.zib.de) based on the new method describes in Schmitt et al. (submitted).

Description: Hydrographic data and seawater samples were collected in four stations along a cross-shore transect in front of the Port of Mazatlán (Mexico) during the oceanographic cruises Maz IV (April 2018) and Maz V (April 2019) on board the R/V “El Puma” (UNAM). Temperature, dissolved oxygen, salinity, and chlorophyll-a fluorescence profiles were measured with a SBE-19plus CTD probe equipped with a WET labs fluorometer sensor. Seawater samples for nutrient analyses were collected at different depths based on the oxygen and chlorophyll-a profiles: surface (5 m depth); mixed layer, deep chlorophyll maximum (at 10–45 m depth); oxycline, base of the oxycline (at 60–125 m depth); upper OMZ (only for Maz V); OMZ core (at 250 m depth); and bottom (between 23 m depth in S1 and 670 m depth in S4). Seawater samples were filtered through cellulose acetate syringe filters (0.22-μm pore, Merck Millipore) and nutrient analyses were determined using a Skalar San-Plus segmented-flow autoanalyzer.

Description: Seawater samples were collected with 10-L Niskin bottles in four stations along a cross-shore transect in front of the Port of Mazatlán (Mexico) during the oceanographic cruises Maz IV (April 2018) and Maz V (April 2019) on board the R/V “El Puma” (UNAM). Samples for molecular analyses (16S rRNA sequences) were collected at different depths based on the oxygen and chlorophyll-a profiles: surface (5 m depth); deep chlorophyll maximum (at 10–45 m depth, except in the coastal station S1 of Maz V where a sample was collected at the mixed layer); base of the oxycline (at 60–125 m depth); OMZ core (only for Maz IV at 250 m depth); and bottom (between 23 m depth in S1 and 670 m depth in S4). Water samples were filtered on board through polycarbonate membranes (0.22-μm pore, Merck Millipore). Genomic DNA was extracted with the DNeasy PowerWater Kit (Qiagen). The V3–V4 region of the 16S rRNA gene was amplified using the index and adaptor-linked primers Bakt_341F and Bakt_805R, and then sequenced using a 2 × 300 bp paired-end Illumina Miseq system. Amplicon libraries were analyzed with the software QIIME 2.

Description: Thermokarst lagoons develop in permafrost lowlands along the ice-rich Arctic coast when thermokarst lakes or basins with bottom elevations at or below sea level are breached by the sea due to erosion, sea-level rise, or connection via drainage channels. Thermokarst lagoons, as dynamic landforms at the interface of terrestrial permafrost and marine systems, play a crucial role in the transformation of permafrost carbon under rising marine influence. Here we present a comprehensive dataset consisting of the first manual thermokarst lagoon area mapping, a more precise number of thermokarst lagoons and a detailed lagoon classification for thermokarst lagoons along the pan-Arctic coast from Taymyr Peninsula in Russia to the Tuktoyaktuk Peninsula in Canada. This is an updated dataset based on the previous work of Jenrich et al. 2021 and Jenrich et al. 2023. The main improvements include (1) counting thermokarst lagoons individually within a lagoon system, as long as the distinct round form of former lake basins is visible; (2) manually calculating the area for all mapped thermokarst lagoons based on the updated Global Surface Water Dataset from 1984-2021 by Pekel et al., 2016; and (3) classifying lagoons based on connectivity to the sea into 5 connectivity classes. We identified 520 thermokarst lagoons covering an area of 3457 km2. Methods: Pan-Arctic thermokarst lagoon distribution and area were mapped using QGIS version 3.34 and Google Earth Engine. The updated Global Surface Water Dataset by Pekel et al., 2016, based on Landsat-5, -7, and -8 satellite images from 1984-2021, was used to create masks with a threshold of 〉75% based on water occurrence, which enabled the manual splitting of polygons from the resulting mask vector data and extraction of thermokarst lagoon areas. Mapping and area extraction also relied on Sentinel-2 imagery from 2023/07/01-2023/08/30, basemaps Google Satellite and ESRI Satellite, and the digital elevation model ArcticDEM and its hillshade HSarcticDEM (Porter et al., 2018). The thermokarst lagoon classification employed a geomorphological approach based on Sentinel-2 imagery and basemaps Google Satellite and ESRI Satellite. Connectivity classes were visually defined and attributed to thermokarst lagoons based on: 1) the size of the lagoon opening relative to its overall size, 2) whether it was directly connected or subsequent within a lagoon system, and 3) interactivity within the lagoon system. The five classes range from 5 - very high connectivity to 1 - very low connectivity: 5 - Lagoon, always open (Lao) - Very high connectivity - Lagoon in direct exchange with the sea. 4 - Lagoon, mostly open (Lmo) - High connectivity - Barrier islands or sand spits only slightly block exchange with the sea or subsequent lagoon which is very well connected to the primary lagoon. 3 - Lagoon, semi-open (Lso) - Medium connectivity - Exchange limited either temporally or spatially due to barrier islands and sand spits or subsequent lagoon which is well connected to the primary lagoon. 2 - Lagoon, limited open (Llo) - Low connectivity - Exchange very limited due to very small opening or narrow channel or subsequent lagoon which is less connected to primary lagoon due to small channel or high distance. 1 - Lagoon, nearly-closed (Lnc) - Very low connectivity - Exchange strongly limited due to long and narrow channel, or subsequent lagoon with very limited exchange. Temporary lake characteristics are possible.

Description: Here we present sedimentological, micropalaeontological, inorganic and organic geochemical, palaeomagnetic, geochronological, and sediment physical data obtained from successional drill cores 1R to 5R at MARUM-MeBo70 Site PS104_21-3 (73.31°S,107.11°W; 882 m water depth). The site is located within the Pine Island cross-shelf trough in the Amundsen Sea Embayment (ASE), West Antarctica and was drilled during RV Polarstern Expedition PS104 in 2017.

Description: This data set has biological measurements and stomach content analysis for fourteen specimens of Centrolophus niger which were frozen whole at sea during the Icelandic part of the International Ecosystem Summer Survey in Nordic Seas (IESSNS) in July 2017 and July 2021. In 2017, three specimens were collected to confirm species identification by a specialist at home institute. In 2021, all caught specimens were collected for detailed biological study. The C. niger were by-catch in a scientific pelagic ecosystem survey which includes trawling, cod-end mesh size 50 mm, in the surface layer, trawl headline visible in surface and foot rope at approximately 35 m depth. For detailed information about the surveys see the cruise reports attached to the campaigns. The data is provided by the Marine and Freshwater Research Institute (MFRI) in Iceland.

Description: This is a hydrographic dataset containing CTD cast and rosette bottle data from two consecutive cruises (NEG2017 and NorthGreen) on the research vessel RV Dana between 23-08-2017 and 01-10-2017 of 2017 on the Northeast Greenland shelf. Both cruises took place between 73.3197 to 80.0519 latitude and 2.1011 to 21.2039 longitude (decimal). The NEG2017 cruise took place from 23 August 2017 to 11 September 2017 was part of the Strategic Environmental program for Northeast Greenland with as its goal to provide environmental impact information pertaining to potential oil exploitation and oil spill response activities in the region. The cruise leader for NEG2017 was Eva Friis Møller. The NorthGreen2017 cruise took place directly after the first between 11 September 2017 and 1 October 2017. It aimed to collect data pertaining to hydroraphical and environmental changes on the shelf. The cruise leader for the NorthGreen2017 cruise was Marit-Solveig Seidenkrantz.

Description: Here we present palynological, palaeomagnetic, and sediment physical data obtained from successional drill cores 1R to 3R at MARUM-MeBo70 Site PS104_21-2 (73.31°S,107.11°W; 882 m water depth). The site is located within the Pine Island cross-shelf trough in the Amundsen Sea Embayment (ASE), West Antarctica and was drilled during RV Polarstern Expedition PS104 in 2017. The site is less than a kilometer away from MARUM-MeBo70 Site PS104_21-3.

Description: Glaciological mass balance parameters are measured as part of the monitoring program at Mullwitzkees in the Hohe Tauern Range, Austria, since the 2006/07 hydrological season. The data sets include glacier wide subseasonal, seasonal and annual point mass balance for the ablation stake and snow pit network, as well as records of snow depth probing. Fixed date values for the hydrological season (winter: 1 Oct - 30 Apr; year: 1 Oct - 30 Sep) are derived by extrapolating from the measurement dates closest to the fixed dates. Detailed information is given in Hartl et al. (2024) and in the associated readme files. New data will be added every year.

Description: Glaciological mass balance parameters are measured as part of the monitoring program at Venedigerkees in the Hohe Tauern Range, Austria, since 2011/12. The data sets include glacier wide subseasonal, seasonal and annual point mass balance for the ablation stake and snow pit network, as well as records of snow depth probing. Fixed date values for the hydrological season (winter: 1 Oct - 30 Apr; year: 1 Oct - 30 Sep) are derived by extrapolating from the measurement dates closest to the fixed dates. Detailed Information is given in Hartl et al. (2024) and in the associated readme files. New data will be added every year.

Description: Seawater samples were collected in four stations along a cross-shore transect in front of the Port of Mazatlán (Mexico) during the oceanographic cruise Maz V (April 2019) on board the R/V “El Puma” (UNAM). Samples were collected at different depths based on the oxygen and chlorophyll-a profiles: surface (5 m depth); mixed layer, deep chlorophyll maximum (at 10–45 m depth); oxycline, base of the oxycline (at 60–125 m depth); upper OMZ; OMZ core (at 250 m depth); and bottom (between 23 m depth in S1 and 670 m depth in S4). Total N and P were determined using a Skalar San-Plus segmented-flow autoanalyzer. Dissolved gases were analyzed through the addition of 5 mL of ultrapure helium into the vials to generate a static-headspace equilibration. N2O was analyzed with a Varian 3380 gas chromatograph using an electron capture detector. CH4 was analyzed with a Schimadzu 17A gas chromatograph with a flame ionization detector and a capillary column.

Description: Seawater samples were collected with 10-L Niskin bottles in four stations along a cross-shore transect in front of the Port of Mazatlán (Mexico) during the oceanographic cruises Maz IV (April 2018) and Maz V (April 2019) on board the R/V "El Puma" (UNAM). Samples for molecular analyses (abundance of N-cycling genes) were collected at different depths based on the oxygen and chlorophyll-a profiles: surface (5 m depth); mixed layer, deep chlorophyll maximum (at 10–45 m depth); oxycline, base of the oxycline (at 60–125 m depth); upper OMZ (only for Maz V); OMZ core (at 250 m depth); and bottom (between 23 m depth in S1 and 670 m depth in S4). Water samples were filtered on board through polycarbonate membranes (0.22-μm pore, Merck Millipore). Genomic DNA was extracted with the DNeasy PowerWater Kit (Qiagen). The abundance of N-cycling genes was assessed using the gene copy number of bacterial and archaeal amoA, anammox bacterial 16S rRNA, nirK, nirS, and nrfA, using a StepOnePlus real-time PCR system (Applied Biosystems).

Description: The biological carbon pump is the mechanism by which the organic matter is exported or sequestered in the deep ocean from years to millennia. This downward transport is performed through physical transport of dissolved and particulate organic carbon, the sinking of particles or passive flux, and the active transport by diel and seasonal vertical migrants. The latter mechanism is still poorly studied, and seasonality of this active flux is even less known. We studied active flux by zooplankton in two transects from the productive coastal transition zone off Northwest Africa to the warm oligotrophic ocean. We estimated the metabolic activity from the surface to 900 m depth using the enzymatic activity of the electron transfer system (ETS) as a proxy for respiration. We found zooplankton ETS activity significantly higher during spring than during fall in the mesopelagic zone. Even at similar migrant biomass values, respiratory flux was higher during spring compared to fall due to the important differences in respiration rates in the mesopelagic zone. These striking differences of respiration rates in the mesopelagic zone was mainly due to the smaller body size of zooplankton during the productive season (spring). These results should be considered in models of active carbon export in the ocean. Here, we provide the data compiled during both cruises (spring and fall).

Description: Continental shelves tend to have high standing stocks of organic carbon and high rates of primary production relative to the open ocean and serve as important link between land and the ocean interior and between the sediment and the water column, playing a key role in the N and C balance, and accounting for up to 50% of the total N loss. One of the widest continental shelves in the eastern South Pacific (ESP) is present off central Chile (36°S). This is an important geographic feature in terms of physical and biological interactions owing to the large area available for coupling between the benthic and pelagic systems. In addition, this area is subjected to a strong coastal upwelling during austral spring and summer; when winds shift to a predominantly northward direction, stressing the sea surface layer and producing an intense cross-shelf transport and uplift of Equatorial Subsurface waters (ESSW) over the shelf. The ESSW, characterized by high NO3- and low O2 content, promotes surface fertilization and, subsequently, intense organic matter respiration and remineralization at depth, along with an efflux of subsurface-accumulated N2O (Farías et al. 2009, Cornejo & Farías, 2012). Thus, periods of maximum productivity and intense suboxia, or even anoxia, when diverse electron donors (e.g., organic matter, NH4+, NO2-, H2S) are present, represent a potential hotspot for fixed N removal processes. We present a data set that has been obtained during different FIP cruises (Fondo de Investigaciones Pesqueras) (2005-2009) which consisted of several transects perpendicular to the coast between 35° and 40°S and from the coast to 77.8° W (central Chile). Data collected include classical oceanographic variables including N2O and important greenhouse gas.

Description: Nitrous oxide (N2O) is an important atmospheric trace gas involved in tropospheric warming and stratospheric ozone depletion. The ocean is a net source of this gas, contributing around 25% of global N2O sources, although this emission is highly variable. It is the case of eastern South Pacific, a region with marked zonal gradients, ranging from highly productive and suboxic conditions in coastal upwelling systems to oligotrophic and oxygenated conditions in the subtropical gyre. Indeed, South Pacific Ocean has the largest permanent anticyclonic oceanic gyre which has been described as the most oligotrophic zone in the world ocean. Nitrous oxide concentration in the water column was measured on a transect crossing the Subtropical South Pacific Gyre during the BIOSOPE cruise (austral spring, 2004). This dataset includes nitrous oxide and nutrient concentrations at different depths from French program BIOSOPE, funded by the Centre National de la Recherche Scientifique (CNRS), the Institut des Sciences de l'Univers (INSU), the Centre National d'Etudes Spatiales (CNES), the European Space Agency (ESA), The National Aeronautics and Space Administration (NASA) and the Natural Sciences and Engineering Research Council of Canada (NSERC). Nitrous oxide measurements belong to Concepción University.