Metadata Report for BODC Series Reference Number 1307116

• 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.

Nitrate, phosphate, silicate and ammonium seawater concentrations for BAS cruise JR20061024

Originator's data acquisition and analysis

Discrete samples were taken using a CTD water bottle rosette. Discrete samples were subsampled and passed through a cellulose nitrate membrane (Whatman WCN, pore size 0.45 µm;). All analyses were conducted using a nutrient autoanalyser made up of Technicon MK II single channel colorimeters and Ismatec pumps and custom built reaction manifolds.

Nitrate Determination of nitrate was conducted following the method described by Stainton (1974). Nitrate is reduced to nitrite by passing the sample stream through a transmission tube containing a copper-coated cadmium wire. Nitrite ions diazotise sulphanilamide then couple with N-1-naphthylethylenediamine dihydrochloride to form an azo-dye, the concentration of which is measured by absorbance at 550 nm.

Phosphate Phosphate concentration was determined following a method similar to that described by Tréguer and Le Corre (1975). Orthophosphate ions react with acidified ammonium molybdate in the presence of antimony to form phosphomolbdic acid. This is reduced by ascorbic acid to a 'molydenum blue' complex (Riley and Skirrow, 1975) the concentration of which is measured by absorbance at 630nm.

Silicate The concentration of silicate in seawater was determined using a method based on an industrial method by Technicon (1976). Silicate ions react with ammonium molybdate in acidic conditions producing silicomolybdic acid. This is reduced to a 'molybdenum blue' complex by ascorbic acid (Riley and Skirrow, 1975) and its concentration is measured by absorbance at 660 nm.

Ammonium Ammonia is determined using a variant of the Berthelot reaction. Sodium dichloroisocyanurate is used as a hypochlorite donor (Krom, 1984) and catalysis is performed by potassium ferrocyanide. After reagent additions, the reaction stream is heated to 40°C and formation of 'indophenol blue' is promoted under longwave UV radiation (365 nm). Concentration is measured by absorbance at 630 nm.

See Whitehouse, 1997 for full details of all instrumentation and analysis involved.

References cited

Folkard A.R., 1978 Automatic analysis of seawater nutrients. Fisheries Technical Report, 46, 23.

Krom M.D., 1984 Spectrophotometric determination of ammonia. A study of a modified Berthelot reaction using salicylate and dichloroisocyanurate. The Analyst, 105, 305-316.

Riley J.P. and Skirrow G., 1975. Chemical Oceanography, 3, (2nd Edition), London, Academic Press.

Stainton M.P., 1974. Simple, efficient reduction column for use in the automated determination of nitrate in water. Analytical Chemistry, 46, 1616.

Technicon Instruments Corporation, 1976. Silicates in water and wastewater. Technicon industrial method No 105-71.

Tréguer P. and Le Corre P., 1975. Manuel d'analyse des sels nutritifs dans l'eau de mer (Utilisation de l'AutoAnalyser II, Technicon, 2nd edition). Report laboratoire d'oceanologie chimique, Université de Bretagne Occidentale, Brest, France.

Whitehouse M.J., 1997. Automated Seawater Nutrient Chemistry. British Antarctic Survey, Cambridge.

BODC Data Processing Procedures

Data were received by BODC in spreadsheet format with the nutrient data from various BAS cruises in labeled worksheets (BAS_nutrient_data_1981-2009.xls). The following metadata fields were also included with the data: cruise ID, date, latitude, longitude, event number and pressure.

Parameter codes defined in the BODC parameter dictionary were mapped to the variables as follows:

Nutrient data were received with no associated time for the sampling event. It was therefore deemed necessary to acquire times from the cruise event log, using the event numbers to map the correct times to the nutrient sampling events.

The depth of the water column at each sampling event has been assigned using GMT and GEBCO data.

The data were banked according to BODC standard procedures for sample data. Data were banked as received, with no averaging or other modifications applied.

Data Quality Report

Event JR161_127 appears to have a sample collected at a depth below the water column depth. The bottle depth and ctd pressure, at the time the bottle was fired, were checked and are correct, but it is not possible to obtain a more accurate water depth for this cruise.

Project Information

DISCOVERY 2010

DISCOVERY 2010 will investigate and describe the response of an ocean ecosystem to climate variability, climate change and commercial exploitation. The programme builds on past studies by BAS on the detailed nature of the South Georgia marine ecosystem and its links with the large-scale physical and biological behaviour of the Southern Ocean.

The aim is to identify, quantify and model key interactions and processes on scales that range from microscopic life forms to higher predators (penguins, albatrosses, seals and whales), and from the local to the circumpolar.

Objectives

Assess the links between the status of local marine food webs and variability and change in the Southern Ocean. Develop a linked set of ecosystem models applying relevant marine physics and biology over scales from the local to that of the entire Southern Ocean.

Relevance to Global Science

Ocean ecosystems play a crucial role in maintaining biodiversity, in depositing carbon into the deep ocean, and as a source of protein for humans. However, fishing and climate change are having significant and often detrimental effects. To predict the future state of ocean ecosystems we must develop computer models capable of simulating biological and physical processes on a range of scales from the local to an entire ocean. Developing such predictive models is crucial to the sustainable management of world fisheries and requires integrated analyses of the way whole ecosystems work. DISCOVERY 2010 aims to take this work forward and at the same time help manage the South Georgia and South Sandwich Islands maritime zone. We will do this through providing information on the state of the ecosystem to the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), the international body that manages sustainable fishing in the Southern Ocean.

Delivering the Results

DISCOVERY 2010 will undertake an integrated programme of shipboard and land-based field studies of the marine food web, combined with modelling. We will pay particular attention to critical phases in the life cycles of key species, and to examining interactive effects in food webs. Interacting biological and physical processes will be modelled across a range of spatial scales to significantly improve our representation of the ocean ecosystem, upon which sustainable management and the prediction of future climate change can be based. DISCOVERY 2010 will link to BIOFLAME, ACES, and COMPLEXITY, two international programmes, and to a collaborative programme with the University of East Anglia on the role of the Southern Ocean in the global carbon cycle.

Component Projects

• DISCOVERY-OEM: Ocean Ecosystems and Management
• DISCOVERY-FOOD-WEBS: Scotia Sea FOOD-WEBS
• DISCOVERY-FLEXICON: FLEXIbility and CONstraints in life histories
• DISCOVERY-CEMI: Circumpolar Ecosystems; Modelling and Integration

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for JR20061024_CTD_JR161_129

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.

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: