Metadata Report for BODC Series Reference Number 1880594

• 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

Non-toxic (underway) sea water supply

A source of uncontaminated near-surface (commonly 3 to 7 m) seawater pumped continuously to shipboard laboratories on research vessels. There is typically a temperature sensor near the intake (known as the hull temperature) to provide measurements that are as close as possible to the ambient water temperature. The flow from the supply is typically directed through continuously logged sensors such as a thermosalinograph and a fluorometer. Water samples are often collected from the non-toxic supply. The system is also referred to as the underway supply.

AMT14 extracted chlorophyll-a measured fluormetrically from CTD bottle and underway samples

Data Acquisition and Analysis

Size-fractionated measurements were only performed on samples collected from the CTD rosette sampler. Total chlorophyll was analysed on samples collected from both the CTD rosette sampler and the ship's non-toxic water supply. During AMT14 underway samples were collected every 2 hrs. Water-column sampling during AMT14 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 at 29 stations on a total of 140 samples. Methodology for size-fractionation was not detailed in the AMT14 cruise report but was confirmed to be the same as that used for AMT13 by originator. 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 2 Excel spreadsheets. The CTD (including size-fractionated data) were accessioned under BODC archive SOC040122 and the underway samples under BODC archive SOC040147. Sample metadata provided (CTD cast, date, time, lat/lon and depth) were checked against information held in the database. There were 3 discrepancies noted and these have now been checked with the originator:

- excessive difference in depth for station AMT14_06 between originator's depths and BODC's CTD depths: closest match to samples attributed to 100 and 150 m were 81.1 and 176.3 m respectively. Originator agreed with correction.

- the surface sample from station AMT14_10 corresponds to a Niskin bottle reported as having misfired in UKORS' CTD log sheets. This was also observed with Mike Zubkov's AFC data. Following enquiry, originator confirmed that the sample did indeed originate from that particular bottle and that some water had been collected despite the misfiring problem.

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 following values were reported as suspect by the originator and were flagged 'L' in the database:

AMT14_38, 46m : value for 0.2-2µm size fraction ("Incorrect measurement")

AMT14_63, 50m: value for >10µm size-fraction ("too high")

AMT14_67, 57m: value for 0.2-2µm ("too low, bad measurement")

AMT14_85, 45m: value for 0.2-2µm ("too low, not extracted properly")

Two values (AMT14_06, 176 m and AMT14_09, 7.6 m) were found suspect during the calibration of the CTD fluorometer and were flagged 'M' in the database.

Problem Report

Not relevant to this dataset.

AMT14 pigment composition by HPLC analysis from surface underway samples

Data Acquisition and Analysis

Seawater samples were collected every 2 hours from the surface underway supply. All samples and replicates were stored at -80 °C and were returned to the National Oceanography Centre, Southampton 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 accession SOC050049. The file was provided to BODC with date, time, lat and lon as metadata. Sample metadata were checked against information held in the database - there were no discrepancies.

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. Tchl data were provided by the originator, but were not loaded to the database as the data were derived values calculated as the sum of Chla and Dvchla values.

The parameter code mapping is shown in the table below:

Data Quality Report

The originator quality checked the dataset and indicated data that were considered suspect. These data have been flagged accordingly in the database.

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

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: