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EARTH SCIENCE > OCEANS > OCEAN CHEMISTRY > NITRATE

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  • Environmental descriptors that are available for the study area (-180 degrees W/+180 degrees E; -45 degrees/-78 degrees S) and for the following periods: 1955-1964, 1965-1974, 1975-1984, 1985-1994, 1995-2012. They were compiled from different sources and transformed to the same grid resolution of 0.1 degree pixel. We also provide future projections for environmental descriptors established based on the Bio-Orable database (Tyberghein et al. 2012). They come from IPCC scenarii (B1, AIB, A2) for years 2100 and 2200 (IPCC, 4th report).

  • Overview of the project and objectives: Assessing the contribution of the different N substrates to the primary production process, such as the biogenic silica production and dissolution in the Antarctic sea-ice provides a means to understand the biogeochemical system functioning. In such a semi closed-type system, assess incorporation rates of HCO3-, NO3-, NH4+, SiOH4, BSi dissolution, nitrification, C-release in close-by ice-cores (3 ice-cores dedicated to (i) 13C-assimilation + 15NH4+ uptake rate, (ii) 13C-assimilation + 15NO3- uptake rate and nitrification, (iii) Biogenic silica production and dissolution via 30Si isotope tool) will allow improving the knowledge of system functioning. This is also closely linked to the thematic of iron availability since these experiments are done close to / on the Trace Metal site allowing us to hopefully propose a relatively complete image of biogeochemical activity and relationship with trace metals on this site. Methodology and sampling strategy: Most of the time we worked close to / directly on the Trace Metal site following precautions concerning TM sampling (clean suits etc.). When we worked close to the TM site, precautions were not such important because we don't need the same drastic precautions for our own sampling. We work together because we want to propose a set of data which helps to characterize the system of functioning in close relation with TM availability (for that, sampling location have to be as close as possible). 14C and 13C-incubation experiment intercalibration work were conducted on the Biosite (different place than TM site except for station 7) Incubation experiment samples are analyzed via (1) Elemental Analyzer - Isotope Ratio Mass Spectrometer (EA-IRMS) for carbon and nitrogen (VUB, Brussels, Belgium); (2) High Resolution Inductively Coupled Mass Spectrometer (HR-ICPMS) for silicon (RMCA, Brussels, Belgium).

  • Overview of the project and objectives: To investigate whether nitrate uptake and processes other than nitrate uptake by phytoplankton are significant and show spatial variability possibly induced by varying availability of Fe and other parameters in the region, seawater was collected from CTD (Conductivity, Temperature and Depth) and TMR (Trace Metals Rosette) casts jointly with the nutrient sampling, as well as well as sea-ice collected from Bio ice-core types on Ice Station, for analysis of nitrate d15N, d18O isotopic composition. Results have been interpreted in the light of prevailing nitrate-nutrient concentrations (Belgian team) and N-uptake regimes for the Ice Stations (new vs. regenerated production and nitrification; see Silicon, Carbon and Nitrogen in-situ incubation Metadata file). Methodology and sampling strategy: Samples for isotopic composition of nitrate were collected from the CTD rosette, TMR and Bio ice-core jointly with the nutrient sampling. Sea-ice sampling: sampling strategy follows ice stations deployment via Bio ice-core type. Most of the time we worked close to / directly on the Trace Metal site following precautions concerning TM sampling (clean suits etc.). When we worked close to the TM site, precautions were not such important because we don't need the same drastic precautions for our own sampling. We work together because we want to propose a set of data which helps to characterize the system of functioning in close relation with TM availability (for that, sampling location have to be as close as possible). All samples were filtered on 0.2 microns acrodiscs and kept at -20 degrees C till analysis in the home-based laboratory. We applied the denitrifier method elaborated by Sigman et al. (2001) and Casciotti et al. (2002). This method is based on the isotopic analysis of delta 15N and delta 18O of nitrous oxide (N2O) generated from nitrate by denitrifying bacteria lacking N2O-reductase activity. As a prerequisite the nitrate concentrations need to be known (nutrients analysis in the home lab.) as this sets sample amount provided to the denitrifier community. Briefly, sample nitrate is reduced by a strain of denitrifying bacteria (Pseudomonas aureofaciens) which transform nitrate into N2O, but lack the enzyme to produce N2. N2O is then analysed for N, O isotopic composition by IRMS (Delta V, Thermo) after elimination of CO2, volatile organic carbon and further cryogenic focusing of N2O (Mangion, 2011). Casciotti K.L., D.M.Sigman, M.G. Hastings, J.K. Bohlke and A. Hilkert, 2002. Measurement of the oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method, Analytical Chemistry, 74 (19): 4905-4912. Mangion P., 2011. Biogeochemical consequences of sewage discharge on mangrove environments in East Africa, PhD Thesis, Vrije Universiteit Brussel, 208 pp. Sigman D.M., Casciotti K.L., Andreani M., Barford C., Galanter M. and J.K. Bohlke, 2001. A bacterial method for the nitrogen isotopic analysis of nitrate in seawater and freshwater, Analytical Chemistry, 73: 4145-4153.

  • Overview of the project and objectives: To investigate whether the Nitrogen - Silicon - Carbon biogeochemical system functions in the Antarctic Marginal Ice Zone and shows spatial variability possibly induced by varying availability of Fe and other parameters in the region. This toolbox is part of project 4051 - samples were taken (1) on the same sea-ice site or very close than the one used for Trace Metal sampling; (2) via Trace Metal Rosette TMR; (3) via Conductivity Temperature and Depth CTD Rosette. It is also part of project 4073 since some intercalibration studies were conducted in collaboration with the primary production team. Three main tools were used which can be either independently or intricately studied. For this reason the complete set of sampling done for this stable isotope toolbox is summarized in one excel file which is duplicated and attached to three child metadata records. Same reasoning for raw data acquired on boar and on field information. This parent metadata record has thus three child metadata records. Each of the child metadata files explain individually the different approaches which were treated together by the same team to resolve the main question of sea-ice biogeochemical system functioning via the use of stable isotope ratio tools. The details of each are in the respective metadata records. The data are attached to this metadata record. METADATA FILES are: - 13C, 15N, 30Si in-situ incubation experiments during SIPEX 2 - Nitrogen and oxygen isotopic composition of nitrate during SIPEX 2 - Delta13C signal of brassicasterol and cholesterol in the Antarctic Sea-ice / Is there particulate barium in sea-ice?

  • This is the CTD and Niskin bottle data set from the RV Tangaroa cruise tan0704, 7th Mar 2007 to 29th Mar 2007, along the Macquarie Ridge. This was the deployment cruise for the Macquarie Ridge mooring array. Dissolved oxygen data have been removed from this data set (oxygen bottle data never analysed). There were a total of 75 CTD casts on this cruise.

  • Oceanographic measurements were conducted on and around the Antarctic shelf in the vicinity of the Mertz Glacier during the southern summer of 2007/2008, on Aurora Australis voyage au0803, V3 2007/2008. Data were collected as part of the CASO (oceanography) and CEAMARC (fishing) programs. The CASO program included occupation of the southern portion of the SR3 transect, plus additional transects down the slope. A total of (130) CTD vertical profile stations were taken, most to within 15 m of the bottom. Over (1400) Niskin bottle water samples were collected for the measurement of salinity, dissolved oxygen, nutrients, CFCs, dissolved inorganic carbon, alkalinity, oxygen-18, germanium, and biological parameters, using a 24 bottle rosette sampler. Full depth current profiles were collected by a lowered acoustic Doppler profiler (LADCP) attached to the rosette package, while near surface current data were collected by a ship mounted ADCP. Additional CTD profiles were taken at 2 subantarctic sites on the transit south. An array of 4 current meter and thermosalinograph moorings were deployed across a basin outflowing from the Mertz Polynya region.

  • Oceanographic measurements were collected aboard Aurora Australis cruise au1203, voyage 3 2011/2012, from 5th January to 12th February 2012. The cruise commenced with opportunistic CTD's in the region of the Adelie Depression and the former Mertz Glacier ice tongue, followed by a full south to north occupation of the CLIVAR/WOCE meridional section I9S. A total of 95 CTD vertical profile stations were taken on the cruise, most to within 15 metres of the bottom. Over 1500 Niskin bottle water samples were collected for the measurement of salinity, dissolved oxygen, nutrients (phosphate, nitrate+nitrite and silicate), dissolved inorganic carbon (i.e. TCO2), alkalinity, pH, barium (dissolved), and biological parameters, using a 24 bottle rosette sampler. Full depth current profiles were collected by an LADCP attached to the CTD package, while upper water column current profile data were collected by a ship mounted ADCP. Meteorological and water property data were collected by the array of ship's underway sensors. An array of 5 current meter moorings was recovered from the Antarctic continental slope at the south end of the I9S transect.

  • Oceanographic measurements were collected aboard RV Investigator cruise in1805 (CSIRO voyage designation in2018_v05) from 16th October to 16th November 2018, along a number of transects across a standing meander of the Antarctic Circumpolar Current between 148o and 156oE. A total of 77 CTD vertical profile stations were taken on the cruise, most to within 12 metres of the bottom. Over 1900 Niskin bottle water samples were collected for the measurement of salinity, dissolved oxygen, nutrients (phosphate, nitrate+nitrite, silicate, ammonium and nitrite), chlorophyll, POC and DOC, and for incubation experiments, using a 36 bottle rosette sampler. Full depth current profiles were collected by an LADCP attached to the CTD package. Upper water column current profile data were collected by a ship mounted ADCP (75 kHz and 150 kHz). Data coverage was increased by additional transects towing a Triaxus towed CTD system. A microstructure profiler was deployed at many of the CTD stations. Meteorological and water property data were collected by the array of ship's underway sensors. An oceanographic mooring was deployed at 55o 32.544’S , 150o 52.332’E, and a series of floats and drifters were deployed. Bathymetry was collected by the ship’s multibeam system. The data set contains CTD 2dbar averaged data, and Niskin bottle data (core hydrochemistry of salinity, dissolved oxygen and nutrients), in text and matlab formats, and a full data report. A WOCE (CCHDO) 'exchange' format version of the data is also available on request.

  • Oceanographic measurements were collected aboard Aurora Australis cruise au1402, voyage 2 2014/2015, from 5th December 2014 to 25th January 2015. The cruise commenced with a Casey resupply, followed by work around the Dalton Polynya/Moscow University Iceshelf/Totten Glacier system, and then around the Mertz Glacier region. A total of 141 CTD vertical profile stations were taken on the cruise, most to within 11 metres of the bottom. Over 1000 Niskin bottle water samples were collected for the measurement of salinity, dissolved oxygen, nutrients (phosphate, nitrate+nitrite and silicate), dissolved inorganic carbon (i.e. TCO2), alkalinity, helium, 18O, and biological parameters, using a 24 bottle rosette sampler. Full depth current profiles were collected by an LADCP attached to the CTD package, and bottom video footage was collected by a camera system (also mounted to the CTD package) for most casts. Upper water column current profile data were collected by a ship mounted ADCP. An underway CTD system (P.I. Alex Orsi, Texas A and M University) was used to collected measurements from the aft of the ship along several small transects around the Dalton Polynya. Meteorological and water property data were collected by the array of ship's underway sensors. 10 'Argo equivalent' floats were also deployed in both the Totten and Mertz regions, for an ice float pilot study. Six oceanographic moorings were recovered from around the Dalton Polynya, three Australian and three US (for the US moorings: P.I.'s Alex Orsi, Texas A and M University, Amy Leventer, Colgate University, and Eugene Domack, University of South Florida). Three temporary acoustic sound source moorings were also deployed then recovered in the same area, in support of an autonomous glider deployment (P.I. Craig Lee, University of Washington). Three oceanographic moorings were recovered from the Mertz region, two Australian and one French (P.I. Marie-Noelle Houssais, Universite Pierre et Marie Curie, for the French mooring). The data set here includes the CTD and Niskin bottle data, in both text and matlab format. The included README file gives full details on file formats.

  • From the abstract and introduction of ANARE Research Notes 44 - ADBEX I cruise to the Prydz Bay region, 1982: nutrient data. Nitrate, phosphate and silicate concentrations obtained during the ADBEX I cruise to the Prydz Bay region in November and December 1982 are plotted with depth and the raw data are tabulated. Location of the sampling stations and the average concentration of each nutrient in the top 100 m of the water column is mapped. The ADBEX I (Antarctic Division BIOMASS Experiment) cruise is part of a long-term, national program of field surveys aimed at fulfilling the objectives of the BIOMASS (Biological Investigation of Marine Antarctic Systems and Stocks) program. The ADBEX I cruise on MV Nella Dan to the Prydz Bay region between 19 November and 17 December 1982, is the second Antarctic Division cruise to contribute to BIOMASS, the first being FIBEX (First International Biomass Experiment) in 1981. Nutrient data were collected at twenty-eight of the seventy-nine hydrographic stations to provide information for the interpretation of phytoplankton distribution and abundance. The sampling locations and depths were not selected, therefore, on the basis of nutrient-related considerations. The concentration of nitrate, phosphate and silicate is plotted to 600 m for each station and where casts were much deeper or much shallower, a second plot is shown. To show water column structure at the time of sampling, sigma-t values were also plotted, unless data for a cast were unavailable. In addition to the depth profiles, the average concentration to 100 m of each nutrient species is mapped to give a first-order approximation of the horizontal pattern of nutrient distribution in the upper layers.