Metadata Report for BODC Series Reference Number 611458

• 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 Quality Report

For many purposes a degree of uncertainty in the instrument depth has little consequence: there is no doubt that it was deployed in the illuminated mixed layer and at sufficient depth to avoid problems with fluorescence quenching. However, great caution should be exercised if any attempt is made to use the data in calculations which require the light level, and hence the meter depth, to be known accurately.

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

Aquatracka fluorometer

The Chelsea Instruments Aquatracka is a logarithmic response fluorometer. It uses a pulsed (5.5 Hz) xenon light source discharging between 320 and 800 nm through a blue filter with a peak transmission of 420 nm and a bandwidth at half maximum of 100 nm. A red filter with sharp cut off, 10% transmission at 664 nm and 678 nm, is used to pass chlorophyll-a fluorescence to the sample photodiode.

The instrument may be deployed either in a through-flow tank, on a CTD frame or moored with a data logging package.

Further details can be found in the manufacturer's specification sheet.

Data Processing Notes

Logging Procedures

During the deployment the fluorometer was operated on an hourly cycle. In each cycle, the fluorometer was powered up for 10 seconds and flashed for 3 minutes logging a data value every 3 seconds (60 in all). The fluorometer was then powered down until the next logging cycle was due. On recovery the battery logging unit was interfaced to a micro computer and a time stamp, mean voltage and standard deviation was determined for each logging cycle.

Calibration Procedures

The voltage was calibrated in terms of pigment concentration using the following procedure. The dark voltage (F0) was determined before and after deployment by measuring the fluorometer output whilst preventing light entering the detector window. Calibration samples were obtained by mounting the fluorometer on the CTD frame in continuous logging mode and collecting water samples using the CTD rosette.

The extracted pigments (chlorophyll and phaeopigment) were determined on desiccated, frozen samples using a Turner Designs bench fluorometer. Further details are given in Mills and Tett (1990). The pigment concentrations (chlorophyll + w*phaeopigment where w is a weighting factor varied from 0 to 1 to optimise fit) were regressed against transformed fluorometer voltage (F*) where:

• F* = 10.0**((F-F0)/c2)
• F = Fluorometer voltage (V)
• F0 = Dark voltage
• c2 = Volts per decade output (manufacturer's setting is 2 V per decade)

The slope is the compound fluorescence emission coefficient (E). Pigment concentrations were then calculated from logged transformed voltages using the equation:

• Pigment concentration (mg/m3) = F*/E

The fluorometer serial no. SA113 was used for both deployments at Survey Site A and for the March deployment at Survey Site E and the fluorometer serial no. SA109 was used for the April deployment at Survey Site E. The calibration of instrument Serial No. SA113 gave values of 0.937 for F0 and 0.683 for E. For logistical reasons, no calibration sample data were available for SA109 and consequently the calibration for SA113 had to be used.

Additional BODC Processing

The time channel data were converted from BST to GMT and gaps were infilled with absent data values. The time series were visually inspected using in house software on a graphics workstation and a small number of points were flagged as suspect.

References

Mills D.K. and Tett P.B. (1990). Use of a Recording fluorometer for continuous measurement of phytoplankton concentration pp106-115 in Environment and pollution measurement sensors and systems (ed. H.O. Nielsen). Proceedings Society of Photo-Optical Instrumentation Engineers (SPIE), 14-15 March 1990, The Hague, Netherlands, Vol.1269, 1990 (198pp).

Project Information

North Sea Project

The North Sea Project (NSP) was the first Marine Sciences Community Research project of the Natural Environment Research Council (NERC). It evolved from a NERC review of shelf sea research, which identified the need for a concerted multidisciplinary study of circulation, transport and production.

The ultimate aim of the NERC North Sea Project was the development of a suite of prognostic water quality models to aid management of the North Sea. To progress towards water quality models, three intermediate objectives were pursued in parallel:

• Production of a 3-D transport model for any conservative passive constituent, incorporating improved representations of the necessary physics - hydrodynamics and dispersion;
• Identifying and quantifying non-conservative processes - sources and sinks determining the cycling and fate of individual constituents;
• Defining a complete seasonal cycle as a database for all the observational studies needed to formulate, drive and test models.

Proudman Oceanographic Laboratory hosted the project, which involved over 200 scientists and support staff from NERC and other Government funded laboratories, as well as seven universities and polytechnics.

The project ran from 1987 to 1992, with marine field data collection between April 1988 and October 1989. One shakedown (CH28) and fifteen survey cruises (Table 1), each lasting 12 days and following the same track, were repeated monthly. The track selected covered the summer-stratified waters of the north and the homogeneous waters in the Southern Bight in about equal lengths together with their separating frontal band from Flamborough head to Dogger Bank, the Friesian Islands and the German Bight. Mooring stations were maintained at six sites for the duration of the project.

Alternating with the survey cruises were process study cruises (Table 2), which investigated some particular aspect of the science of the North Sea. These included fronts (nearshore, circulation and mixing), sandwaves and sandbanks, plumes (Humber, Wash, Thames and Rhine), resuspension, air-sea exchange, primary productivity and blooms/chemistry.

In addition to the main data collection period, a series of cruises took place between October 1989 and October 1990 that followed up work done on previous cruises (Table 3). Process studies relating to blooms, plumes (Humber, Wash and Rhine), sandwaves and the flux of contaminants through the Dover Strait were carried out as well as two `survey' cruises.

The data collected during the observational phase of the North Sea Project comprised one of the most detailed sets of observations ever undertaken in any shallow shelf sea at that time.

Data Activity or Cruise Information

Data Activity

North Sea Project POLRIG#C51AF

Deployment

The fluorometer mooring was deployed as part of the North Sea Project Survey at Site A.

Mooring description

The fluorometer package comprised of an Aquatracka logarithmic response fluorometer and a battery logger unit (BLU) enclosed in a stainless steel protective cage. The package was incorporated into a POL 'U' shaped mooring (a surface toroid buoy at one end and a sub-surface buoy at the other end) suspended between the anchor chain and the sub-surface buoy with three 11 inch trawl floats immediately above the fluorometer.

The position of the fluorometer in the water column is open to question. In the mooring specification a nominal depth of 10m below the sea surface was requested. During inventory compilation, a figure of 7m below sea surface was obtained although subsequent re-investigation has been unable to identify the source of this information. In Mills and Tett (1990) the fluorometer is shown 18m below the surface in a diagram of the mooring, but described as being between 8 and 15m from the surface in the text. A figure of 8.5m (the mean of the two values, 7 and 10 metres, available when the data were prepared) has been used in the headers of the data files.

References

Mills D.K. and Tett P.B. (1990). Use of a Recording fluorometer for continuous measurement of phytoplankton concentration pp106-115 in Environment and pollution measurement sensors and systems (ed. H.O. Nielsen). Proceedings Society of Photo-Optical Instrumentation Engineers (SPIE), 14-15 March 1990, The Hague, Netherlands, Vol.1269, 1990 (198pp).

Fixed Station Information

Fixed Station Information

North Sea Project Survey Mooring Site A and CTD Site CS

Site A was one of six fixed stations where moorings were deployed during the North Sea Project survey. This location is also one of 123 North Sea Project CTD Sites.

The site was characterised by weak tidal currents, up to a maximum of 0.5 m/s, and the water column was stratified in summer months.

The rigs deployed here lie within a box bounded by co-ordinates 55.493N 0.893E at the southwest corner and 55.563N 0.920E at the northeast corner. Magnetic variation at this site was 4.5° west.

Site A deployment history is summarised below:

ADCP = Acoustic Doppler Current Profiler
CM = Current Meter (Aanderaa or S4)
THCH = Thermistor Chain
FL = Fluorometer

Related Fixed Station activities are detailed in Appendix 1

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: NSP Survey A and CTD Site CS

Related series for this Fixed Station 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.