Metadata Report for BODC Series Reference Number 1256772

• 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

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.

Nutrients for cruises Charles Darwin CD94 and RRS Discovery DI216

Document History

Converted from CDROM documentation.

Content of data series

Data Originator

Professor Mike Orren, University College Galway, Ireland.

Sampling strategy and methodology

Samples were collected from either bottles on the CTD rosette or the continuously pumped surface sea water supply and analysed using an Alpkem autoanalyser. This machine and the chemistries employed for phosphate and silicate were progressively modified during the project in an attempt to obtain reasonable performance. The following modifications were described:

The length of all tubing was reduced to the absolute minimum.

The instrument was thoroughly cleaned with Decon90 before each procedure.

The phosphate determination wavelength was switched to 760 nm, with wash and sample times switched to 60 and 30 seconds respectively.

The wavelength used for silicate was switched to 795 nm. The ascorbic acid reagent was prepared without the recommended acetone addition, the sulphuric acid concentration was doubled and the ammonium molybdate was filtered prior to each procedure.

Samples were generally analysed on board ship but some samples taken towards the end of a cruise had to be analysed back in the laboratory. These were kept in the dark and as cool as possible between collection and analysis.

Comments on data quality

Charles Darwin CD94

A subset of the nutrient channels (NO₃+NO₂, PO4 and silicate) were measured by both Hamburg and Galway universities. Both data sets included a small number of anomalous data values. These have been flagged suspect ('M') together with data from bottles where there is strong evidence of contamination through leakage.

The nitrate+nitrite and silicate data from the two groups compare extremely well and no systematic difference between the two data sets could be established. On some casts the Hamburg data were slightly higher whilst on other casts it was the Galway data that were slightly higher.

Regressing the two data sets gave the following results:

Nitrate+nitrite Galway = Hamburg * 0.9591 + 0.4471 (R² = 98%)
Silicate Galway = Hamburg * 1.0188 - 0.1091 (R² = 99%)

The results for phosphate were not as good. The Galway values were systematically significantly lower than the Hamburg data, sometimes by as much as 50%. The intercalibration plot exhibited much more scatter than the plots for the other two nutrients.

Regressing the two data sets gave the following result:

Phosphate Galway = Hamburg * 0.9234 - 0.0939 (R² = 83%)

The Hamburg data compare more favourably with data from other cruises where the phosphate values are believed to be good quality. It is therefore recommended that the Galway phosphates be used with caution, bearing in mind that they are probably low. However, either nitrate+nitrite or silicate data set may be used with confidence.

RRS Discovery DI216

Nutrients were measured by three groups on this cruise: nitrate+nitrite, silicate and phosphate were measured by SOC; phosphate was determined manually by ULB; nitrate+nitrite and silicate were determined by the Galway group.

The ULB and SOC phosphate data show very good agreement. ULB reported some phosphate samples contaminated and these have been flagged 'L' in the database.

The SOC data are believed to be of extremely high quality. Indeed the data were used successfully to identify CTD rosette misfires due to the close proximity of the values from unintentional 'blind duplicates'. The only problem encountered with the SOC data were the nitrate+nitrite values for one cast (CTD4) which were obviously low. This was attributed to the reduction column being poisoned by mercury in an internal standard and the data have been flagged.

The Galway data from CTD bottles were compared with the SOC data and flagged if they deviated from the SOC values by more than 10 per cent. The same 'blind duplicates' described above were analysed by Galway but the replication was very poor. Users are recommended to use the SOC data rather than the Galway data whenever possible.

Samples from the continuous sea water supply were not analysed by SOC. The Galway data are erratic and in many cases incredibly high. With the exception of samples taken on a section up the Channel right up to the Solent, surface nitrate+nitrite values in excess of 0.75 µM and silicate values in excess of 1.0 µM have been flagged suspect by BODC. The remaining data should be used with caution.

References

Armstrong, F.A.J., Stearns, C.R. and Strickland, J.D.H., 1967. The measurement of upwelling and subsequent biological processes by means of the Technicon Autoanalyser and associated equipment. Deep Sea Res. 14, 381-389.

Eberlein, K. and Kattner, G. 1987. Automatic method for the determination of ortho-phosphate and total dissolved phosphorus in the marine environment. Fresenius Z. anal. Chem., 326, 354-357.

Elskens, I. and Elskens, M., 1989. Handleing voor de bepaling van nutrienten in zeewater met an Autoanalyser IITM systeem. Vrije Universiteit Brussel, 50pp..

Føyn, L., Magnussen, M. and Seglem, K., 1981. Automatisk analyse av naeringsalter med "on-line" databehandling. En presentasjon av oppbyggning og virkemåte av systemet i bruk på Havforskningsinstituttets båter og i laboratoriet. Fisken Hav., Ser. B., 4, 1-40.

Goeyens, L,. Kindermans, N., Yusuf, M.A. and Elskens, M. (submitted 1996). A room temperature procedure for the manual determination of urea in seawater. Submitted to Marine Chemistry.

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

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

Mourino, C. and Fraga, F., 1985. Determinacion de nitratos en aqua de mar. Investigacion Pesquera, 49, 81-96.

Mulvena, P. and Savidge, G., 1992. A modified manual method for the determination of urea in seawater using diacetylmonoxime reagent. Estuarine, Coastal and Shelf Science, 34, 429-438.

Murphy, J. and Riley, J.P., 1962. A modified single solution method for the determination of phosphate in natural waters. Analytica Chim. Acta, 27, 31-36.

Rees, A.P., Owens, N.J.P. and Woodward, E.M.S. (1995). Phytoplankton nitrogen assimilation at low nutrient concentrations in the NW Mediterranean Sea. Water Pollution Research Report 32 in EROS 2000 ed J-M Martin and H. Barth, European Commission, 141-148.

Project Information

Ocean Margin EXchange (OMEX) I

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 I (1993-1996)

The first phase of OMEX was divided into sub-projects by discipline:

• Physics
• Biogeochemical Cycles
• Biological Processes
• Benthic Processes
• Carbon Cycling and Biogases

This emphasises the multidisciplinary nature of the research.

The project fieldwork focussed on the region of the European Margin adjacent to the Goban Spur (off the coast of Brittany) and the shelf break off Tromsø, Norway. However, there was also data collected off the Iberian Margin and to the west of Ireland. In all a total of 57 research cruises (excluding 295 Continuous Plankton Recorder tows) were involved in the collection of OMEX I data.

Data Availability

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

• OMEX I Project Data Set (two 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 DI216_CTD_CTD39

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: DI216_CTD_CTD39

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