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Metadata Report for BODC Series Reference Number 1264840

Metadata Summary

Data Description

Data Category Water sample data
Instrument Type
Niskin bottle  discrete water samplers
Instrument Mounting lowered unmanned submersible
Originating Country Spain
Originator Dr Xosé Álvarez Salgado
Originating Organization Institute of Marine Research, Vigo
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) OMEX II-II

Data Identifiers

Originator's Identifier BG9815C_CTD_NUTS_112:03A
BODC Series Reference 1264840

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1998-06-28 12:25
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -

Spatial Co-ordinates

Latitude 42.15120 N ( 42° 9.1' N )
Longitude 9.32265 W ( 9° 19.4' W )
Positional Uncertainty Unspecified
Minimum Sensor or Sampling Depth 8.7 m
Maximum Sensor or Sampling Depth 201.0 m
Minimum Sensor or Sampling Height 19.4 m
Maximum Sensor or Sampling Height 211.7 m
Sea Floor Depth 220.4 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Unspecified -
Sensor or Sampling Depth Datum Unspecified -
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface


BODC CODERankUnitsTitle
ADEPZZ011MetresDepth (spatial coordinate) relative to water surface in the water body
AMONAATX1Micromoles per litreConcentration of ammonium {NH4+ CAS 14798-03-9} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis
BOTTFLAG1Not applicableSampling process quality flag (BODC C22)
NTRIAATX1Micromoles per litreConcentration of nitrite {NO2- CAS 14797-65-0} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis
NTRZAATX1Micromoles per litreConcentration of nitrate+nitrite {NO3+NO2} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis
PHOSAATX1Micromoles per litreConcentration of phosphate {PO43- CAS 14265-44-2} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis
SAMPRFNM1DimensionlessSample reference number
SLCAAATX1Micromoles per litreConcentration of silicate {SiO44- CAS 17181-37-2} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis

Definition of BOTTFLAG

0The sampling event occurred without any incident being reported to BODC.
1The filter in an in-situ sampling pump physically ruptured during sample resulting in an unquantifiable loss of sampled material.
2Analytical evidence (e.g. surface water salinity measured on a sample collected at depth) indicates that the water sample has been contaminated by water from depths other than the depths of sampling.
3The feedback indicator on the deck unit reported that the bottle closure command had failed. General Oceanics deck units used on NERC vessels in the 80s and 90s were renowned for reporting misfires when the bottle had been closed. This flag is also suitable for when a trigger command is mistakenly sent to a bottle that has previously been fired.
4During the sampling deployment the bottle was fired in an order other than incrementing rosette position. Indicative of the potential for errors in the assignment of bottle firing depth, especially with General Oceanics rosettes.
5Water was reported to be escaping from the bottle as the rosette was being recovered.
6The bottle seals were observed to be incorrectly seated and the bottle was only part full of water on recovery.
7Either the bottle was found to contain no sample on recovery or there was no bottle fitted to the rosette position fired (but SBE35 record may exist).
8There is reason to doubt the accuracy of the sampling depth associated with the sample.
9The bottle air vent had not been closed prior to deployment giving rise to a risk of sample contamination through leakage.

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

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

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.


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.

Nutrients for cruises Belgica BG9714C and BG9815C, Charles Darwin CD105B, CD110B and CD114A and Professor Shtokman ST0898

Document History

Converted from CDROM documentation

Content of data series

AMONAAD2 Dissolved ammonium
Colorimetric autoanalysis (0.4/0.45µm pore filtered)
AMONAAD5 Dissolved ammonium
Colorimetric autoanalysis (0.2µm pore filtered)
AMONAATX Dissolved ammonium
Colorimetric autoanalysis (unfiltered)
AMONMATX Ammonium (unfiltered)
Manual Colorimetric analysis (unfiltered)
NTRIAAD2 Dissolved nitrite
Colorimetric autoanalysis (0.4/0.45µm pore filtered)
NTRIAAD5 Dissolved nitrite
Colorimetric autoanalysis (0.2µm pore filtered)
NTRIAATX Nitrite (unfiltered)
Colorimetric autoanalysis (unfiltered)
NTRZAAD2 Dissolved nitrate + nitrite
Colorimetric autoanalysis (0.4/0.45µm pore filtered)
NTRZAAD5 Dissolved nitrate + nitrite
Colorimetric autoanalysis (0.2µm pore filtered)
NTRZAATX Nitrate + nitrite (unfiltered)
Colorimetric autoanalysis (unfiltered)
PHOSAAD2 Dissolved phosphate
Colorimetric autoanalysis (0.4/0.45µm pore filtered)
PHOSAAD5 Dissolved phosphate
Colorimetric autoanalysis (0.2µm pore filtered)
PHOSAATX Phosphate (unfiltered)
Colorimetric autoanalysis (unfiltered)
PHOSMATX Phosphate (unfiltered)
Manual Colorimetric analysis (unfiltered)
SLCAAAD2 Dissolved silicate
Colorimetric autoanalysis (0.4/0.45µm pore filtered)
SLCAAAD5 Dissolved silicate
Colorimetric autoanalysis (0.2µm pore filtered)
SLCAAATX Silicate (unfiltered)
Colorimetric autoanalysis (unfiltered)
SLCAMATX Silicate (unfiltered)
Manual Colorimetric analysis (unfiltered)
UREAMDD2 Dissolved urea
Manual analysis using the diacetylmonoximeµmethod (0.4/0.45µm pore filtered)
UREAMDTX Urea (unfiltered)
Manual analysis using the diacetylmonoxime method

Data Originator

Dr Xosé A. Alvarez-Salgado, IIM, Vigo, Spain.

Sampling strategy and methodology

Different sampling strategies were employed on different cruises. Logistics for CD110B and BG9815C allowed analysis of the samples at sea. In these cases, the samples were drawn from the CTD bottles into 50ml polyethylene containers and preserved at 4 °C until they were analysed on board. For other cruises the samples were filtered through Whatman polypropylene filters (0.45µm pore size) into 50ml polyethylene containers and preserved by freezing at -20 °C until analysed in the laboratory at IIM.

In both cases, nutrient concentrations were determined colorimetrically using an Alpkem Corporation auto-analyser, working under the principle of Segmented Flow Analysis (SFA).

The data were generally supplied to BODC in units of micromoles per kilogram (converted by the originator assuming a density of 1.025 kg/litre) with nitrate and nitrite supplied as separate channels. These have been converted to units of micromoles/litre (by multiplying by 1.025) and NO3 and NO2 have been added to give a NO3+NO2 channel. The exception was the data from CD114A that were supplied in intercalibration format with NO2 and NO3+NO2 in units of micromoles per litre. These data have been loaded to the database unmodified.

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.


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


The Alpkem Corporation analyser performed with a high degree of accuracy during the cruise.

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:

Slope Y Intercept R2
Nitrate 1.04 0.00 1.00
Phosphate 0.85 0.01 0.92
Silicate 0.70 -0.47 0.98
Ammonium 0.27 0.22 0.11

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.


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.

Project Information

Ocean Margin EXchange (OMEX) II - II


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


Cruise Name BG9815C
Departure Date 1998-06-27
Arrival Date 1998-07-06
Principal Scientist(s)Michel Frankignoulle (University of Liège Department of Astrophysics Geophysics and Oceanography)
Ship RV Belgica

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:

Flag Description
Blank Unqualified
< Below detection limit
> In excess of quoted value
A Taxonomic flag for affinis (aff.)
B Beginning of CTD Down/Up Cast
C Taxonomic flag for confer (cf.)
D Thermometric depth
E End of CTD Down/Up Cast
G Non-taxonomic biological characteristic uncertainty
H Extrapolated value
I Taxonomic flag for single species (sp.)
K Improbable value - unknown quality control source
L Improbable value - originator's quality control
M Improbable value - BODC quality control
N Null value
O Improbable value - user quality control
P Trace/calm
Q Indeterminate
R Replacement value
S Estimated value
T Interpolated value
U Uncalibrated
W Control value
X Excessive difference

SeaDataNet Quality Control Flags

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

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain
B nominal value
Q value below limit of quantification