Metadata Report for BODC Series Reference Number 1704749

• 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 supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

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.

AMT13 extracted chlorophyll-a (total and size-fractionated) measured fluormetrically from CTD bottle and underway samples

Data Acquisition and Analysis

Total chlorophyll was analysed on samples collected from both the CTD rosette sampler and from a small number of underway samples collected from the ship's non-toxic water supply. Water-column sampling during AMT13 concentrated around 5 or 6 light depths from the predawn CTD cast (~0200 - 0400h local time), with a reduced set of depths from the late morning 'optics' cast (1100h local time).

Water samples from the 5-6 main light depths were collected from CTD bottles and underway samples from the ship's non-toxic supply and these samples were filtered on 25 mm GFF filters. Filters were extracted in 90% acetone for 10-24 hrs and total chlorophyll-a measured with a TD-700 Turner Designs fluorometer following the procedure of Welschmeyer (1994) which minimises interference by chlorophyll-b. The fluorometer was calibrated with dilutions of a solution of pure chlorophyll-a (Sigma, UK) in 90% acetone, the concentration of which was determined spectrophotometrically after the cruise.

Size-fractionation of chlorophyll was carried out for samples collected on the pre-dawn cast. Size-fractionated chlorophyll distribution was determined by serial filtration onto 10, 5, 2 and 0.2 µm polycarbonate membrane filters (Poretics, UK). The filters were treated identically to the GF/F used for total chlorophyll and were soaked in 10-ml 90% acetone (HPLC grade) for 10-24 hours prior to reading on the bench fluorometer.

References Cited

Welschmeyer N.A., 1994. Fluorometric analysis of chlorophyll-a in the presence of chlorophyll-b and phaeopigments. Limnology and Oceanography, 39, 1985-1992.

Instrumentation Description

Not relevant to this dataset.

BODC Data Processing Procedures

Data were submitted to BODC in an Excel spreadsheet and were accessioned under BODC archive SOC040010. Sample metadata provided (CTD cast, date, time, lat/lon and depth) were checked against information held in the database. There were no discrepancies noted.

Parameter codes defined in BODC parameter dictionary were assigned to the variable. The units supplied in the spreadsheet were mg m^-3, which match the Parameter Dictionary units so no unit conversions were necessary.

Data loaded into BODC's database without any changes applied.

A parameter mapping table is provided below;

Data Quality Report

The data originator removed any suspect data before submission to BODC.

Problem Report

Not relevant to this dataset.

AMT13 pigment composition by HPLC analysis from CTD bottle samples

Data Acquisition and Analysis

Fresh seawater samples from upto five light depths were collected from 57 stations during the cruise. The main sampling was conducted on the pre-dawn cast each day with a reduced set of samples from the midday cast. All samples and replicates were stored at -80 °C and were returned to SOC in liquid-N for analysis.

HPLC analysis was carried out according to Barlow et al. (1997).

References Cited

Barlow R.G., Cummings D.G. and Gibb S.W., 1997. Improved resolution of mono- and divinyl chlorophylls a and b and zeaxanthin and lutein in phytoplankton extracts using reverse phase C8 HPLC. Marine Ecology Progress Series, 161 , 303-307.

Instrumentation Description

Section not relevant.

BODC Data Processing Procedures

Data were submitted to BODC in Microsoft Excel spreadsheet format and saved to the archive with reference SOC040134. The file was provided to BODC with CTD cast number, date, and bottle depth as metadata.

Sample metadata were checked against information held in the database - there was one minor depth discrepancy. Data were provided from a sample collected from 160m during cast 21, but no bottle was fired at this depth instead bottles were fired at 150m and the data were loaded against this depth.

Parameter codes defined in BODC parameter dictionary were assigned to the variables as shown in the table below. Values were multiplied by one thousand where appropriate for conversion into nanograms per litre. Cells where a value was logged as 'Present' were changed to 0 and the flag '<' was added to show values were below the detection level of the instrument. Column headings were substituted for the appropriate BODC parameter code except for Tpigm and Tchla, which were derived from the summation of all pigment values and ChlA and Dv ChlA values repectively. These derived values were not loaded into the database.

Data loaded into BODC's database without any changes.

Data Quality Report

The following values were reported as suspect by the originator and were flagged 'L' in the database: AMT13_30, 12m: Value for DV ChlA too low. AMT13_65, 52m: Value for DV ChlA too high.

Problem Report

This section is 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 AMT13_CTD_A13_05

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: AMT13_CTD_A13_05

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