Metadata Report for BODC Series Reference Number 2280481

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

Data Access Policy

Open Data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

Narrative Documents

Niskin Bottle

The Niskin bottle is a device used by oceanographers to collect subsurface seawater samples. It is a plastic bottle with caps and rubber seals at each end and is deployed with the caps held open, allowing free-flushing of the bottle as it moves through the water column.

Standard Niskin

The standard version of the bottle includes a plastic-coated metal spring or elastic cord running through the interior of the bottle that joins the two caps, and the caps are held open against the spring by plastic lanyards. When the bottle reaches the desired depth the lanyards are released by a pressure-actuated switch, command signal or messenger weight and the caps are forced shut and sealed, trapping the seawater sample.

Lever Action Niskin

The Lever Action Niskin Bottle differs from the standard version, in that the caps are held open during deployment by externally mounted stainless steel springs rather than an internal spring or cord. Lever Action Niskins are recommended for applications where a completely clear sample chamber is critical or for use in deep cold water.

Clean Sampling

A modified version of the standard Niskin bottle has been developed for clean sampling. This is teflon-coated and uses a latex cord to close the caps rather than a metal spring. The clean version of the Levered Action Niskin bottle is also teflon-coated and uses epoxy covered springs in place of the stainless steel springs. These bottles are specifically designed to minimise metal contamination when sampling trace metals.

Deployment

Bottles may be deployed singly clamped to a wire or in groups of up to 48 on a rosette. Standard bottles and Lever Action bottles have a capacity between 1.7 and 30 L. Reversing thermometers may be attached to a spring-loaded disk that rotates through 180° on bottle closure.

Nitrogen and oxygen isotope measurements of nitrate from CTD bottles during cruise AMT16

Originator's Protocol for Data Acquisition and Analysis

This data originates from analyses on samples collected from CTD bottles between 20 May and 29 June 2005. Samples were taken from a meridional cross section from the Northen Gyre through the equatorial upwelling zone to the Northen Gyre. Samples were also taken from the euphotic zone.

Water samples were collected from selected bottle depths and selected CTD casts. Approximately 60 ml of sample was drawn into clear acid-cleaned Nalgene flasks, tightly capped and frozen at -20 °C.

The 15N/14N and 18O/16O isotope ratios were analysed using the denitrifier method (see Casciotti et al., 2002 and Sigman et al., 2001 for detailed methods) The method of measurement of the isotopic composition of nitrate is based on the isotopic analysis of nitrous oxide (N2O) generated from nitrate in denitrifying bacteria that lack N2O reductase activity. Firstly, the denitrifying culture is prepared; organic nitrogen in a tryptic soy broth and ammonium is added to the culture medium to provide nitrogen for assimilation. Cultures are incubated for six to ten days on a reciprocol shaker. To convert the samples to nitrous oxide, samples are centrifuged then decanted and alliquotted into 20 ml headspace vials. Each vial is purged with N2 gas. The water sample is then injected into each vial and incubated overnight. Extraction and isotopic analysis of nitrous oxide is carried out by stripping N20 from each vial using a helium gas carrier then purifying the sample and analysing its isotopic composition using an isotope ratio mass spectrometer.

References Cited

Casciotti, K.L., Sigman, D.M., Hastings, M.G., Bohlke, J.K., Hilkert, A. 2002. Measurement of the oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method. Analytical Chemistry 74, 4905-4912, doi:10.1021/ac020113w.

Sigman, D.M., Casciotti, K.L., Andreani, M., Barford, C., Galanter, M., Bohlke, J.K. 2001. A bacterial method for the nitrogen isotopic analysis of nitrate in seawater and freshwater. Analytical Chemistry 73, 4145-4153.

Instrumentation Description

Not applicable for this data set.

BODC Data Processing Procedures

Data were submitted in an Excel spreadsheet (AMT16_Nitrate_isotope_data_Casciotti_9Nov2009.xls) and archived under BODC's accession number WHC090227. Nutrient data were also supplied but not loaded with this dataset as these data have been previously supplied. The standard deviation of samples were provided and loaded with the dataset. Sample metadata (CTD cast, bottle number and depth) were checked against information held in the database and against the cruise CTD bottle firing logsheets. There were a number of depth discrepancies between the originators depth-bottle number combinations and those on the CTD logsheets for CTD029t. The bottle numbers were considered correct and bottle number 2 was loaded against 500 m (CTD log) instead of 300 m (originator's file), bottle number 3 was loaded against 300 m (CTD log) instead of 150 m (originator's file) and bottle number 4 against 150 m (CTD log) instead of 100 m (originator's file). There was no bottle fired at 100 m during CTD029t. For CTD043t, there was a difference between the intended firing depth (recorded on the CTD logsheets) and the actual depth (contained in the Seabird bottle files) of 11 m . In addition, CTD027t was provided with a typo in the latitude, 14.255°S, which should have been 4.255°S. 109 CTD samples were loaded in total.

The isotopic enrichment data were provided in parts per thousand which is consistent with the BODC parameter code units, so no conversion was applied.

The data were reformatted and loaded in BODC's samples database under Oracle Relational Database Management System. Data were marked up with BODC parameter codes and loaded into the database. Individual samples were matched through rosette sampling bottle and depth.

A parameter mapping table is provided below;

Data Quality Report

BODC was not advised of any specific quality issues with the data. The data were checked visually; no values were flagged by BODC.

Problem Report

Not relevant to this data set.

Project Information

The Atlantic Meridional Transect - Phase 2 (2002-2006)

Who was involved in the project?

The Atlantic Meridional Transect Phase 2 was designed by and implemented by a number of UK research centres and universities. The programme was hosted by Plymouth Marine Laboratory in collaboration with the National Oceanography Centre, Southampton. The universities involved were:

• University of Liverpool
• University of Newcastle
• University of Plymouth
• University of Southampton
• University of East Anglia

What was the project about?

AMT began in 1995, with scientific aims to assess mesoscale to basin scale phytoplankton processes, the functional interpretation of bio-optical signatures and the seasonal, regional and latitudinal variations in mesozooplankton dynamics. In 2002, when the programme restarted, the scientific aims were broadened to address a suite of cross-disciplinary questions concerning ocean plankton ecology and biogeochemistry and the links to atmospheric processes.

The objectives included the determination of:

• how the structure, functional properties and trophic status of the major planktonic ecosystems vary in space and time
• how physical processes control the rates of nutrient supply to the planktonic ecosystem
• how atmosphere-ocean exchange and photo-degradation influence the formation and fate of organic matter

The data were collected with the aim of being distributed for use in the development of models to describe the interactions between the global climate system and ocean biogeochemistry.

When was the project active?

The second phase of funding allowed the project to continue for the period 2002 to 2006 and consisted of six research cruises. The first phase of the AMT programme ran from 1995 to 2000.

Brief summary of the project fieldwork/data

The fieldwork on the first three cruises was carried out along transects from the UK to the Falkland Islands in September and from the Falkland Islands to the UK in April. The last three cruises followed a cruise track between the UK and South Africa, only deviating from the traditional transect in the southern hemisphere. During this phase the research cruises sampled further into the centre of the North and South Atlantic Ocean and also along the north-west coast of Africa where upwelled nutrient rich water is known to provide a significant source of climatically important gases.

Who funded the project?

Natural Environment Research Council (NERC)

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for AMT16_CTD_CTD029s

Please note:the supplied parameters may not have been sampled from all the bottle firings described in the table above. Cross-match the Sample Reference Number above against the SAMPRFNM value in the data file to identify the relevant metadata.

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Appendix 1: AMT16_CTD_CTD029s

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

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