Metadata Report for BODC Series Reference Number 2122735

• 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

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.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

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.

AMT21 (D371) extracted chlorophyll-a measurements from CTD bottle samples

Originator's Protocol for Data Acquisition and Analysis

Samples were taken from 8 - 10 CTD rosette bottles to provide a calibration for the fluorometer measurements on each rig. During the cruise 655 samples were collected from 73 CTD casts and processed for extracted chl-a measurements.

At each sampling a 250 ml sample of seawater collected from the non-toxic supply was filtered through a 0.2 µm polycarbonate filter. The chlorophyl-a was then extracted from the filters with 10ml 90% acetone for 24 hours while samples were stored in a freezer. The concentrations were then determined fluorometrically following Welschmeyer (1994).

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

Turner Designs Trilogy fluorometer with a non-acidified chl module (CHL NA #046) fitted

BODC Data Processing Procedures

Data were submitted after the cruise and archived under BODC's accession number BOD120006. The extracted chlorophyll-a data were provided in a file with sample metadata (cruise ID, event number, CTD, station, date, time in UT, latitude and longitude, rosette bottle number, depth and sample bottle ID). The cruise, CTD number, date, time, latitude and longitude metadata were already loaded to the database from the cruise event log - the metadata combinations in the file matched those in the database. The depth and rosette position metadata were already loaded from the Sea-Bird bottle firing files - the depth and rosette position combinations in the file matched those in the database.

Where replicate samples were provided from a niskin bottle the mean and standard deviation have been calculated and entered into the database. No unit conversion was necessary as the units the data were supplied in the files matched the units for the parameter codes in the BODC Parameter Dictionary.

A parameter mapping table is provided below;

Data Quality Report

The discrete sample data were compared with the fluorometer profiles for each CTD cast during the cruise. For 21 samples the measurements were considered suspect. Two of these suspect samples relate to replicate samples from the same Niskin bottle and the mean and standard deviation for these have been entered in the database. These data have been flagged accordingly in the database.

Problem Report

Not relevant to this data set.

CTD Data at bottle firing depths

These data were obtained by BODC software that extracts CTD downcast data (or upcast data if the downcast is unavailable) at depths corresponding to those at which the bottles were fired. The software applies an offset, if present, to the minimum and maximum pressures recorded during bottle firing to account for the distance between the CTD sensor and the mid-point along the bottle. The mean of this depth range is used to find the corresponding CTD data values by interpolation. BODC store these data to enable comparison between CTD and discrete bottle sample data.

Further metadata can be found by searching for the relevant cruise summary report in the BODC cruise inventory. The full CTD profile corresponding to these data is available via the BODC 'all series' application.

Project Information

Oceans 2025 Theme 10, Sustained Observation Activity 1: The Atlantic Meridional Transect (AMT)

The Atlantic Meridional Transect has been operational since 1995 and through the Oceans 2025 programme secures funding for a further five cruises during the period 2007-2012. The AMT programme began in 1995 utilising the passage of the RRS James Clark Ross between the UK and the Falkland Islands southwards in September and northwards in April each year. Prior to Oceans 2025 the AMT programme has completed 18 cruises following this transect in the Atlantic Ocean. This sustained observing system aims to provide basin-scale understanding of the distribution of planktonic communities, their nutrient turnover and biogenic export in the context of hydrographic and biogeochemical provinces of the North and South Atlantic Oceans.

The Atlantic Meridional Transect Programme is an open ocean in situ observing system that will:

• give early warning of any fundamental change in Atlantic ecosystem functionng
• improve forecasts of the future ocean state and associated socio-economic impacts
• provide a "contextual" logistical and scientific infrastructure for independently-funded national and international open ocean biogeochemical and ecological research.

The specific objectives are:

• To collect hydrographic, chemical, ecological and optical data on transects between the UK and the Falkland Islands
• To quantify the nature and causes of ecological and biogeochemical variability in planktonic ecosystems
• To assess the effects of variability in planktonic ecosystems on biogenic export and on air-sea exchange of radiatively active gases

The measurements taken and experiments carried out on the AMT cruises will be closely linked to Themes 2 and 5. The planned cruise track also allows for the AMT data to be used in providing spatial context to the Sustained Observation Activities at the Porcupine Abyssal Plain Ocean Observatory (SO2) and the Western Channel Observatory (SO10).

More detailed information on this Work Package is available at pages 6 - 9 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10

Weblink: http://www.oceans2025.org/

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for D371_CTD_CTD036

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: D371_CTD_CTD036

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.