Metadata Report for BODC Series Reference Number 1264458

• 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

Public domain 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.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

Narrative Documents

Nutrients for cruises Charles Darwin CD105B and Belgica BG9714B, BG9714C, BG9714D, BG9815C, BG9815D, BG9919A, BG9919B and BG9919C

Document History

Converted from CDROM documentation

Content of data series

Data Originator

Dr Lei Chou, ULB, Brussels, Belgium.

Sampling strategy and methodology

Manual spectrophotometric analyses for phosphate and silicate were done using the methods specified in Grasshoff et al. (1983). These analyses were usually carried out on board ship as soon after sampling as possible. Samples were kept refrigerated and dark between collection and analysis.

Samples for nutrient determination by autoanalysis were kept frozen until analysed. A separate set of samples were usually taken specifically for silicate analysis and stored in the dark, chilled but not frozen. Samples were analysed on a SKALAR autoanalyser.

Comments on data quality

The following comments on data quality were either included in the cruise report by the analyst or notes made during the BODC data audit.

CD105B

The determination of ammonia concentrations was problematic due to the contamination of the Milli-Q system onboard, which prevented a reliable baseline being established.

BG9919 (all legs)

The silicate analyses were carried out on frozen samples over a year after the cruise, as no chilled samples were available. Users are therefore requested to treat the silicate data from all legs of this cruise with caution.

Nutrient Intercalibration

Many efforts were made during the period of OMEX II-II to compare nutrient data produced from different laboratories. The 'formal' Work Package 4 intercalibration was based on samples collected during two contemporaneous cruises in June 1997. The following is summarised from the intercalibration report.

Intercalibration samples were taken from cruise CD105B and analysed by Plymouth Marine Laboratory, the Instituto de Investigaçiones Marias (IIM) and University of Brussels (ULB). At Stations S90, S200 and S2250, samples were taken from the CTD bottle, filtered through acid-washed, 0.45 m cellulose nitrate filters and then sub-sampled. One sub-sample was analysed onboard Charles Darwin, and four were immediately frozen. Of these, three were transferred to Belgica (BG9714B) for analysis, and one was returned to PML for later analysis. On 20/06/97, simultaneous CTD casts were made from Charles Darwin and Belgica, and 24 replicate samples were analysed on both ships.

The following table summarises the results of the comparison between PML and IIM:

A regression of the nitrate concentrations determined by the two laboratories shows almost perfect agreement with a slope of 1.04 for the fitted line, an intercept of zero and an R²value of 1.00. The phosphate intercalibration was also good with R² of 0.85. However, the slope was no longer unity and the IIM estimates were higher than those of the PML. The R² value for the silicate determinations suggests that the precision of both laboratories is good (the regression yields a straight line with R² value of 0.98), but there is a problem with accuracy. In other words, the relative changes in silicate concentration were well described by both laboratories but there is doubt about the absolute value of silicate concentration, with the PML consistently measuring lower concentrations than the IIM. Finally, the analysis of ammonium shows wide variations with the IIM estimates being higher than the PML estimates. However, in the case of ammonium, both precision and accuracy were suspect. This may be a consequence of storage of samples or of contamination on board ship, which is a recognised problem in ammonium determinations.

There was excellent agreement between the phosphate measurements made by the ULB and the PML. The slope of the fitted line was 1.09, the intercept was 0.01 and the R² was 0.99. That is, precision and accuracy were both excellent in these measurements. The silicate data also showed a perfect linear trend with an R² value of 1.00. However, as with the intercalibration of the PML and the IIM, the slope was not unity and the PML estimates were consistently below those obtained by ULB. It is clear that the PML standard silicate solution was not correct

There were a number of other cruises when analysts were present from more than one laboratory and cross-checked results from common samples. Both PML and IIM participated in CD114 and samples collected on ST0898 were analysed by both IEO and IIM. All versions of the data have been loaded into the database and may be retrieved for comparison if required.

References

Brewer, P.G. and Riley, J.P., 1965. The automatic determination of nitrate in seawater. Deep-Sea Research, 12, 765-772.

Garside, C., 1982. A chemiluminescent technique for the determination of nanomolar concentrations of nitrate and nitrite in seawater. Marine Chemistry, 11, 159-167.

Goeyens, L, Kindermans, N, AbuYusuf, M and Elskens, M., 1998. A room temperature procedure for the manual determination of urea in seawater. Estuarine Coastal and Shelf Science. 47: 415-418.

Grasshoff, K., 1976. Methods of seawater analysis. Verlag Chemie, Weiheim. 317pp

Grasshoff, K., Ehrhardt, M. and Kremling, K. eds., 1983. Methods of seawater analysis. Verlag Chemie.

Jones, R.D., 1991. An improved fluorescence method for the determination of nanomolar concentrations of ammonium in natural waters. Limnology and Oceanography, 36, 814-819.

Kirkwood, D., 1989. Simultaneous determination of selected nutrients in sea water. International Council for the Exploration of the Sea (ICES), CM 1989/C:29.

Koroleff, F., 1969. Direct determination of ammonia in natural waters as indophenol blue. Int. Counc. Explor. Sea, CM., 9, 19-22.

Mantoura, R.F.C. and Woodward, E.M.S., 1983. Optimisation of the indophenol blue method for the automated determination of ammonia in estuarine waters. Estuarine, Coastal and Shelf Science, 17, 219-224.

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.

Project Information

Ocean Margin EXchange (OMEX) II - II

Introduction

OMEX was a European multidisciplinary oceanographic research project that studied and quantified the exchange processes of carbon and associated elements between the continental shelf of western Europe and the open Atlantic Ocean. The project ran in two phases known as OMEX I (1993-1996) and OMEX II - II (1997-2000), with a bridging phase OMEX II - I (1996-1997). The project was supported by the European Union under the second and third phases of its MArine Science and Technology Programme (MAST) through contracts MAS2-CT93-0069 and MAS3-CT97-0076. It was led by Professor Roland Wollast from Université Libre de Bruxelles, Belgium and involved more than 100 scientists from 10 European countries.

Scientific Objectives

The aim of the Ocean Margin EXchange (OMEX) project was to gain a better understanding of the physical, chemical and biological processes occurring at the ocean margins in order to quantify fluxes of energy and matter (carbon, nutrients and other trace elements) across this boundary. The research culminated in the development of quantitative budgets for the areas studied using an approach based on both field measurements and modeling.

OMEX II - II (1997-2000)

The second phase of OMEX concentrated exclusively on the Iberian Margin, although RV Belgica did make some measurements on La Chapelle Bank whilst on passage to Zeebrugge. This is a narrow-shelf environment, which contrasts sharply with the broad shelf adjacent to the Goban Spur. This phase of the project was also strongly multidisciplinary in approach, covering physics, chemistry, biology and geology.

There were a total of 33 OMEX II - II research cruises, plus 23 CPR tows, most of which were instrumented. Some of these cruises took place before the official project start date of June 1997.

Data Availability

Field data collected during OMEX II - II have been published by BODC as a CD-ROM product, entitled:

• OMEX II Project Data Set (three discs)

Further descriptions of this product and order forms may be found on the BODC web site.

The data are also held in BODC's databases and subsets may be obtained by request from BODC.

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for BG9815C_CTD_04B

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: BG9815C_CTD_04B

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