Metadata Report for BODC Series Reference Number 1655994

• 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.

Phytoplankton pigment concentration data series for cruise Valdivia VA174

Document History

Converted from CDROM documentation

Data Originator

Paul Tett, Napier University, Edinburgh, UK.

Content of data series

CTD= CTD-Rosette water column sampling station.

Ssampling strategy and methodology

Water samples were collected from 4 to 5 depths using the CTD-rosette water sampler. About 2 litres of seawater were filtered through 47 mm GF/F filters, which were then extracted overnight in buffered 90% acetone. Optical densities (od) were measured against a 90% acetone blank in a Shimadzu UV-1202 spectrophotometer using 50 mm pathlength sub-micro cells. Measurements were made at 750, 665, 664, 647, 630, 510 and 480 nm, and, after addition of 2 drops 1N HCl (od_acid), at 750 and 665 nm. Concentrations of chlorophyll a and phaeopigments were calculated by the Lorenzen method, of chlorophylls a, b and c by the Trichromatic equations (with coefficients of Jeffrey, Humphrey, 1975), and of total carotenoids from the optical densities at 510 and 480 nm.

Lorenzen method:

chlorophyll a (µg l^-1) = A * K * (od₍₆₆₅₎ - od_acid₍₆₆₅₎) * E / (V * p)
pheophytin a (µg l^-1) = A * K * ((R * od_acid₍₆₆₅₎ - od₍₆₆₅₎) * E / (V * p)

where:

A = Lorenzen coefficient for chlorophyll a (11 µg cm ml^-1)
R = chlorophyll a:pheophytin absorbance at 665 nm (1.7)
K = R / (R - 1)

Trichromatic method (SCOR):

chl. a (mg m-3) = (11.85 * od₍₆₆₄₎ - 1.54 * od₍₆₄₇₎ - 0.08 * od₍₆₃₀₎) * E / (V * p)
chl. b (mg m-3) = (-5.43 * od₍₆₆₄₎ + 21.03 * od₍₆₄₇₎ - 2.66 * od₍₆₃₀₎) * E / (V * p)
chl. c1+c2 (mg m-3) = (-1.67 * od₍₆₆₄₎ - 7.60 * od₍₆₄₇₎ + 24.52 * od₍₆₃₀₎) * E / (V * p)

Carotenoids:

carotenoids (mg m-3)= (7.6 * (od₍₄₈₀₎ - 1.49 * od₍₅₁₀₎) * E / (V * p)

where:

E = extract volume (ml)
V = volume of sample water filtered (l)
p = pathlength of cuvette (cm)

BODC processing

In order to standardise parameter units with that held in BODC's database, chlorophyll b and c concentrations were converted from µg l^-1 to ng l^-1 by multiplying their original values by 1000. The rest of the data were loaded into a database under the ORACLE Relational Database Management System without modification.

Comments on data quality

Measurements suffered from high and somewhat variable blanks, and the standard deviation of replicate chlorophyll a estimated by the Lorenzen method was too high (0.19 mg m^-3) for these values to be considered reliable. The standard deviations of replicate estimates of chlorophyll a by the Trichromatic method (0.05 µg l^-1) and of carotenoids (0.06 µg l^-1) were acceptable.

Reference

Jeffrey SW, Humphrey SF (1975) New spectrophotometric equations for determining chlorophylls a, b, c1 and c2 in higher plants, algae and phytoplankton. Biochem. Biophysiol. Planzen, 167, 191-194.

Project Information

PROcesses of Vertical Exchange in Shelf Seas (PROVESS)

Introduction

PROVESS was an interdisciplinary study of the vertical fluxes of properties through the water column and the surface and bottom boundary layers. The project was funded by the European Community MAST-III programme (MAS3-CT97- 0159) and ran from March 1998 to May 2001.

Scientific Rationale

PROVESS was based on the integration of experimental, theoretical and modelling studies with the aim of improving understanding and quantification of vertical exchange processes in the water column, in particular in the surface and benthic boundary layers and across the> pycnocline. PROVESS also explored mechanisms of physical-biological coupling in which vertical exchanges and turbulence significantly affect the environmental conditions experienced by the biota with particular reference to aggregation, flocculation, sedimentation and trophic interactions.

Fieldwork

The experimental phase of the project was carried out at two contrasting sites in the North Sea: the northern North Sea site (NNS) and the southern North Sea site (SNS).

The two sites had the following characteristics:

At both locations measurements were concentrated at a central position with additional measurements being made to estimate horizontal gradients. Moored instruments (including current meters, temperature and pressure sensors, fluorometers, transmissometers, nutrient analysers and meteorological sensors) were deployed between 7 September and 5 November 1998 at the NNS and between 29 March and 25 May 1999 at the SNS. Each experiment was supported by intensive measurement series made from oceanographic ships and involving turbulence dissipation profiler CTD, particle size profilers, optical profilers, benthic sampling and water bottle sampling.

Details of the cruises were as follows:

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for VA174_CTD_053_074

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: