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Metadata Report for BODC Series Reference Number 1702177

Metadata Summary

Data Description

Data Category Water sample data
Instrument Type
Niskin bottle  discrete water samplers
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Dr Andy Lane
Originating Organization National Oceanography Centre, Liverpool
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) Oceans 2025 Theme 10 SO11

Data Identifiers

Originator's Identifier PD21_11_CTD_PIGX_177:cast042
BODC Series Reference 1702177

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2011-07-27 03:58
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -

Spatial Co-ordinates

Latitude 53.44912 N ( 53° 26.9' N )
Longitude 3.64220 W ( 3° 38.5' W )
Positional Uncertainty Unspecified
Minimum Sensor or Sampling Depth 0.6 m
Maximum Sensor or Sampling Depth 20.4 m
Minimum Sensor or Sampling Height 3.3 m
Maximum Sensor or Sampling Height 23.1 m
Sea Floor Depth 23.7 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
BOTTFLAG1Not applicableSampling process quality flag (BODC C22)
CLSDFLP11Milligrams per cubic metreConcentration standard deviation of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and fluorometry
CPHLFLP11Milligrams per cubic metreConcentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and fluorometry
FIRSEQID1DimensionlessBottle firing sequence number
PHAEFLP11Milligrams per cubic metreConcentration of phaeopigments {pheopigments} per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and fluorometry
PHSDFLP11Milligrams per cubic metreConcentration standard deviation of phaeopigments {pheopigments} per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and fluorometry
ROSPOSID1DimensionlessBottle rosette position identifier
SAMPRFNM1DimensionlessSample reference number

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

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.


Bottles may be deployed singly clamped to a wire or in groups of up to 48 on a rosette. Standard bottles have a capacity between 1.7 and 30 L, while Lever Action bottles have a capacity between 1.7 and 12 L. Reversing thermometers may be attached to a spring-loaded disk that rotates through 180° on bottle closure.

Discrete Chlorophyll a and Phaeopigment data measured by NOC, Liverpool on Coastal Observatory cruise 78 (PD21_11)

Sampling Strategy

Discrete chlorophyll and phaeopigment samples were collected by the National Oceanography Centre (NOC), Liverpool on Oceans 2025 SO11 cruise 78 (PD21_11) in Liverpool Bay. The cruise ran from 25 to 28 July 2011 on the RV Prince Madog.

Originators Processing

Pre-processing: The test tubes were cleaned, paired up with screw-caps, numbered and placed in racks.

Sample collection: The filters were Whatman 0.7 µm pore size 47 mm diameter GF/F filters (straight from the box). Tweezers were used to handle the filters at the edges. Clean buckets were placed beneath the Niskin bottles on the CTD frame and the entire contents were taken. The samples were stirred before being measured out, typically 500 ml was required, less if turbid conditions. The pre-weighed filter was placed on to the holder and the funnel assembled. The vacuum pump was switched on and the suction carefully set to <0.2 bar The samples were added in stages and the filter was not allowed to go dry. The filter was then placed in a test tube, the cap was put on and then the tube was wrapped in aluminium foil, labelled and returned to the freezer at -18°C.

Post-processing: A fluorometric method was used: a chlorophyll standard was made and used to calibrate the fluorometer (Turner Designs, USA). The test tubes were taken out of the freezer and 5 ml of cold 90 % acetone was added. The foil wrapped tubes were then put in a polypropylene beaker with water and sonicated in the water bath for 15 minutes. The samples were not allowed to warm up and exposure to high light levels was avoided. The filters were removed from the pigmented acetone and analysed by the fluorometer as soon as was possible. A drop of 10% hydrochloric acid was added to convert chlorophyll to phaeophytin and the sample was then analysed again.

BODC Processing

The data were supplied to BODC as an Excel spreadsheet. This was converted to an ASCII format file for loading into the BODC database. Methodology and units were checked against information held in the BODC parameter dictionary and an appropriate parameter code was attributed to each variable.

Originator's Variable Units BODC Parameter Code Definition of Parameter Code Units Comments
Chlorophyll -a concentration µg l-1 CPHLFLP1 Concentration of chlorophyll-a {chl-a} per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and fluorometry mg m-3 No conversion required as µg l-1 = mg m-3
    CLSDFLP1 Concentration standard deviation of chlorophyll-a {chl-a} per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and fluorometry mg m-3 Standard deviation values calculated by BODC
Concentration of phaeophytin-a µg l-1 PHAEFLP1 Concentration of phaeopigments per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and fluorometry. mg m-3 No conversion required as µg l-1 = mg m-3
    PHSDFLP1 Concentration standard deviation of phaeopigments per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and fluorometry. mg m-3 Standard deviation values calculated by BODC

The data and metadata fields were checked and then loaded into the database under the Oracle Relational Database Management System by matching the sample's station identifier and depth with the information already held in the database for this cruise. Where the data supplied included multiple replicates for each station, the mean value and standard deviation were loaded into the database. For single samples, the data were loaded without further modification. If duplicate samples were supplied but one had been marked as suspect by the originator the alternative value was loaded (rather than a mean and standard deviation being calculated). Data were then quality controlled by BODC and where suspect values were identified flags were applied.

Project Information

Oceans 2025 Theme 10, Sustained Observation Activity 11: Liverpool Bay and Irish Sea Coastal Observatory

Sustained, systematic observations of the ocean and continental shelf seas at appropriate time and space scales allied to numerical models are key to understanding and prediction. In shelf seas these observations address issues as fundamental as 'what is the capacity of shelf seas to absorb change?' encompassing the impacts of climate change, biological productivity and diversity, sustainable management, pollution and public health, safety at sea and extreme events. Advancing understanding of coastal processes to use and manage these resources better is challenging; important controlling processes occur over a broad range of spatial and temporal scales which cannot be simultaneously studied solely with satellite or ship-based platforms.

Considerable effort has been spent by the Proudman Oceangraphic Laboratory (POL) in the years 2001 - 2006 in setting up an integrated observational and now-cast modelling system in Liverpool Bay (see Figure), with the recent POL review stating the observatory was seen as a leader in its field and a unique 'selling' point of the laboratory. Cost benefit analysis (IACMST, 2004) shows that benefits really start to accrue after 10 years. In 2007 - 2012 exploitation of (i) the time series being acquired, (ii) the model-data synthesis and (iii) the increasingly available quantities of real-time data (e.g. river flows) can be carried out through Sustained Observation Activity (SO) 11, to provide an integrated assessment and short term forecasts of the coastal ocean state.

BODC image

Overall Aims and Purpose of SO 11

  • To continue and enlarge the scope of the existing coastal observatory in Liverpool Bay to routinely monitor the northern Irish Sea
  • To develop the synthesis of measurements and models in the coastal ocean to optimize measurement arrays and forecast products. Driving forward shelf seas' operational oceanography with the direct objective of improving the national forecasting capability, expressed through links to the National Centre for Ocean Forecasting (NCOF)
  • To exploit the long time-series of observations and model outputs to: a) identify the roles of climate and anthropogenic inputs on the coastal ocean's physical and biological functioning (including impacts of nutrient discharges, offshore renewable energy installations and fishing activity) taking into consideration the importance of events versus mean storms / waves, river discharge / variable salinity stratification / horizontal gradients; b) predict the impacts of climate change scenarios; and c) provide new insights to Irish Sea dynamics for variables either with seasonal cycles and interannual variability, or which show weak or no seasonal cycles
  • To provide and maintain a 'laboratory' within which a variety of observational and model experiments can be undertaken (Oceans 2025 Themes 3, 6, 8, 9), including capture of extreme events
  • Demonstrate the value of an integrated approach in assessment and forecasting
  • Demonstrate the coastal observatory as a tool for marine management strategies through collaboration with the Environment Agency (EA), Department for Environment, Food and Rural Affairs (DEFRA), Joint Nature Conservation Commmittee (JNCC), English Nature (EN), Department of Agriculture and Rural Development (DARD), and Local Authorities, providing management information pertinent to policy (e.g. Water Framework Directive)

Measurement and Modelling Activities

  • East Mooring Site: Bottom frame with full suite of physical measurements (high frequency Acoustic Doppler Current Profiler (ADCP), conductivity, temperature, turbidity and fluorescence), a Centre for Environment, Fisheries and Aquaculture Science (CEFAS) directional wavebuoy, and a CEFAS Smartbuoy collecting surface properties including salinity, temperature, turbidity, nutrients, irradiance and chlorophyll. All transmit data in real-time via Orbcomm. The Smartbuoy also collects daily water samples.
  • West Mooring Site: Bottom frame with full suite of physical measurements (high frequency ADCP, conductivity, temperature, turbidity and fluorescence), CEFAS Smartbuoy.
  • Spatial Survey: Four - six week intervals (determined by biofouling of optical sensors). Spatial surveys comprise of vertical profiles of CTD, suspended particulate material (SPM), some bed sediment sampling and surface and bed nutrients, phytoplankton, zooplankton.
  • Ferry: The Birkenhead - Belfast ferry samples near surface (5 m depth) temperature, salinity, turbidity, chlorophyll, with data transmitted by Orbcomm. The route is scientifically varied passing through six completely different hydrodynamic regions, which significantly impact on their ecological function.
  • Tide gauges: Real-time data are obtained from tide gauges operated by Mersey Docks and Harbour Company (MDHC) and the UK tide gauge network.
  • Satellite imagery: Weekly composite satellite data, Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature (SST) and ocean colour (chlorophyll and suspended sediment), are provided by the Remote Sensing Data Analysis Service (RSDAS) based at Plymouth Marine Laboratory (PML).
  • HF radar: A phased array HF radar system (a 12-16MHz WERA HF radar) measuring surface currents and waves with maximum range 75km at a resolution of 4km for sea surface currents and for 2-D wave spectra.
  • Meteorology station: With web camera, located on Hilbre Island at the mouth of the Dee Estuary
  • Operational models: The Coastal Observatory uses Proudman Oceanographic Laboratory Coastal Ocean Modelling System (POLCOMS), which is part of Oceans 2025 Theme 9.

More detailed information on this Work Package is available at pages 32 - 35 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10



IACMST., 2004. The Economics of Sustained Marine Measurements. IACMST Information Document, N0.11, Southampton: IACMST, 96 pp

Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 2011-07-27
End Date (yyyy-mm-dd) 2011-07-27
Organization Undertaking ActivityNational Oceanography Centre, Liverpool
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierPD21_11_CTD_cast042
Platform Categorylowered unmanned submersible

BODC Sample Metadata Report for PD21_11_CTD_cast042

Sample reference number Nominal collection volume(l) Bottle rosette position Bottle firing sequence number Minimum pressure sampled (dbar) Maximum pressure sampled (dbar) Depth of sampling point (m) Bottle type Sample quality flag Bottle reference Comments
447320    5.00 3 1   20.90   21.00   20.30 Niskin bottle No problem reported    
447321    5.00 4 2   21.00   21.00   20.40 Niskin bottle No problem reported    
447322    5.00 8 3    5.90    6.80    5.80 Niskin bottle No problem reported    
447323    5.00 9 4    1.00    1.10     .60 Niskin bottle No problem reported    
447324    5.00 10 5    1.00    1.10     .60 Niskin bottle No problem reported    

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 Name PD21/11
Departure Date 2011-07-25
Arrival Date 2011-07-28
Principal Scientist(s)M John Howarth (National Oceanography Centre, Liverpool)
Ship RV Prince Madog

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
Q value below limit of quantification