Metadata Report for BODC Series Reference Number 2144337

• 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.

Dissolved Inorganic Carbon (DIC) measurements from CTD bottle samples collected during CROZEX cruises D285 and D286

Originator's Protocol for Data Acquisition and Analysis

The following methods are taken from the D285/D286 cruise report, please refer to this for further details.

Water samples were collected using a Sea-Bird 9+ standard stainless steel CTD, with aluminium, titanium and plastic instrument housings and 24-way rosette containing 20 L Niskin bottles. A total of 25 standard CTD casts were sampled, as well as 5 thorium casts (15495, 15498, 15539, 15540, 15548). The standard CTD casts were sampled to the bottom, except at station 15489. Typical sampling depths were 10 m, 20 m, 40 m, 60 m, 80 m, 100 m, 150 m, 200 m, 300 m, 400 m, 500 m, 750 m, 1000 m, 1500 m, 2000 m, 2500 m, 3000 m, 3500, bottom -10 m, while leaving out depths, if the water column was shallower. Thus, approximately 400 CTD samples were analysed for DIC.

Samples were collected in 500 ml glass bottles from the Niskin bottles and were generally analysed within 24 hours of collection. If this could not be achieved due to instrument failure or close station spacing, the samples were fixed by adding 100 µl of a saturated mercury chloride solution for each 500 ml sample, stored in the dark in a cold room (5°C) and analysed within 6 days of collection. Samples were kept cold before measurement in a seawater flow. The DIC concentration was determined by coulometric analysis after the method of Johnson et al. (1987). At least three replicate analyses were made on each sample bottle, until two replicates were within 1 µmol kg^-1 (100 counts) for a blank below 0.3 µmol kg^-1 min^-1 (30 counts min^-1). The system had a small carry over effect, such that the first replicate of a sample was discarded, if a strong DIC change occurred between samples and between samples and standards. The instrument was kept running, except when the cell was changed, as this gave the best results. Generally all samples from one cast and sometimes a few samples of another cast were run per cell. The starting up time for a new cell varied from 2 to 8 hours, before the blanks came down sufficiently. The temperature of the samples during analysis was determined with an accurate Pt100 sensor. At least one standard of certified reference material from batches 65 and 66 (DOE, 1994) was used per coulometric cell and per cast.

From 26 November 2004 to 28 November 2004 the instrument blank stayed above 30 counts per minute. During trouble shooting many components of the system were r eplaced: new coulometer chemicals, fresh soda lime from a new pot, a new 4.5 quality nitrogen gas cylinder, a clean extractor for the extractor unit, and a new lamp for the coulometer. Exclusion of the extractor unit from the system showed that the blank problem originated from the carrier gas, the soda lime, the coulometer, or the cell. The carrier gas and ineffective soda lime were the most likely source of the blank problem. The blanks came down after the trouble-shooting.

References Cited

Johnson, K.M., Williams, P.J.LeB., Brandstrom, L., Sieburth, J.McN., 1987. Coulometric total carbon dioxide analysis for marine studies: automatization and calibration. Marine Chemistry 21, 117-;133.

DOE, 1994. Handbook of methods for the analysis of the various parameters of the carbon system in sea water; version 2. Dickson, A.G., C. Goyet (Eds.). ORNL/CDIAC 74.

BODC Data Processing Procedures

Data were supplied to BODC in an excel file, which was reformatted into an ASCII format file and loaded into the BODC database using established BODC data banking procedures. The positions of the bottles on the rosette for D285 were taken from the Sea-Bird .btl files and the rosette positions and bottle firing sequences for D286 were taken from the Sea-Bird .bl files. The beginning and end times for both cruises were taken from table 1.2 in the cruise report. Latitude, longitude and water depths were re-determined for each sample using the underway navigation and bathymetry data based upon the corresponding times. All bottles noted in the cruise report as having suffered from problems (e.g. leaks or misfires) or any data values reported as suspect have been flagged appropriately in the BODC database. Parameters were mapped to standard BODC codes, as detailed in the table below. The data were provided in units per mass and have therefore been stored as such. If the alternative units per volume are required a conversion factor based upon the density calculated from the pressure, potential temperature and salinity at the time when the bottles were fired has been provided.

Data Quality Report

A couple of data values were flagged by the originator.

Problem Report

None (BODC assessment).

Total Alkalinity measurements from CTD bottle samples collected during CROZEX cruises D285 and D286

Originator's Protocol for Data Acquisition and Analysis

The following methods are taken from the D285/D286 cruise report, please refer to this for further details.

Water samples were collected using a Sea-Bird 9+ standard stainless steel CTD, with aluminium, titanium and plastic instrument housings and 24-way rosette containing 20 L Niskin bottles. A total of 25 standard CTD casts were sampled, as well as 5 thorium casts (15495, 15498, 15539, 15540, 15548). The standard CTD casts were sampled to the bottom, except at station 15489. Typical sampling depths were 10 m, 20 m, 40 m, 60 m, 80 m, 100 m, 150 m, 200 m, 300 m, 400 m, 500 m, 750 m, 1000 m, 1500 m, 2000 m, 2500 m, 3000 m, 3500, bottom -10 m, while leaving out depths, if the water column was shallower. Thus, approximately 400 CTD samples were analysed for DIC.

Samples were collected in 500 ml glass bottles from the Niskin bottles and were generally analysed within 24 hours of collection. If this could not be achieved due to instrument failure or close station spacing, the samples were fixed by adding 100 µl of a saturated mercury chloride solution for each 500 ml sample, stored in the dark in a cold room (5°C) and analysed within 6 days of collection.

The alkalinity measurements were made by potentiometric titration with a VINDTA instrument (#4, version 3C) developed by Ludger Mintrop. The burette, the pipette (volume 99 ml), and the analysis cell have a water jacket around them. Samples were kept at room temperature (~18°C) before measurement. The water jackets and two samples, one awaiting analysis and the other being analysed, were kept at a constant temperature of 24.5°C by a recirculation water bath. The temperature was checked regularly by a calibrated mercury thermometer. The titrant (0.1 M hydrochloric acid, HCl) was made by dilution of 50 ml of 1 M HCl with 450 ml of MilliQ. Three different batches of titrant were used. Two or three replicates were run on each sample bottle, until the difference between two replicates was less than 1 µmol kg^-1. The first measurement after restarting the system, a pause in the analysis, or after topping up the electrodes was generally slightly off and was discarded. The instrument was occasionally affected by a carry over effect if there were large differences in alkalinity between successive samples or between samples and the seawater standards. At least one standard of batches 65 or 66 was run per CTD cast, generally after they had been used for DIC analysis. Occasionally a new standard was opened for alkalinity. The alkalinity data need correction for seawater density and nutrient concentrations.

BODC Data Processing Procedures

Data were supplied to BODC in an excel file, which was reformatted into an ASCII format file and loaded into the BODC database using established BODC data banking procedures. The positions of the bottles on the rosette for D285 were taken from the Sea-Bird .btl files and the rosette positions and bottle firing sequences for D286 were taken from the Sea-Bird .bl files. The beginning and end times for both cruises were taken from table 1.2 in the cruise report. Latitude, longitude and water depths were re-determined for each sample using the underway navigation and bathymetry data based upon the corresponding times. All bottles noted in the cruise report as having suffered from problems (e.g. leaks or misfires) or any data values reported as suspect have been flagged appropriately in the BODC database. Parameters were mapped to standard BODC codes, as detailed in the table below. The data were provided in units per mass and have therefore been stored as such. If the alternative units per volume are required a conversion factor based upon the density calculated from the pressure, potential temperature and salinity at the time when the bottles were fired has been provided.

Data Quality Report

None (BODC assessment).

Problem Report

None (BODC assessment).

Project Information

CROZet natural iron bloom EXport experiment (CROZEX)

The multidisciplinary CROZet natural iron bloom EXport experiment (CROZEX) was a major component of the Natural Environment Research Council (NERC) funded core strategic project Biophysical Interactions and Controls over Export Production (BICEP). The project is the first planned natural iron fertilisation experiment to have been conducted in the Southern Ocean.

The overall objective of CROZEX was to examine, from surface to sediment, the structure, causes and consequences of a naturally occurring phytoplankton bloom in the Southern Ocean. The Crozet Plateau was chosen as the study area. This area typically exhibits two phytoplankton blooms a year, a primary bloom in that peaks in October and a secondary bloom in December or January. Specific aims with respect to these were to:

• Determine what limits the primary bloom
• Determine the cause of the secondary bloom

The project was run by the George Deacon Division (GDD), now Ocean Biogeochemistry and Ecosystems (OBE) at the National Oceanography Centre Southampton (NOCS). Participants from five other university departments also contributed to the project.

The project ran from November 2004 to January 2008 with marine data collection between 3^rd November 2004 and 21^st January 2005. There were 2 cruises to the Crozet Islands Plateau, which are summarised in Table 1.

Table 1: Details of the RRS Discovery CROZEX cruises.

The two cruises aimed to survey two areas at different phases of the bloom cycle described above. A control area to the south of the Crozet Islands, which is classified as High Nutrient Low Chorophyll (HNLC), where the blooms do not occur and a second area in the region of the blooms to the north of the Crozet Islands.

Sampling was undertaken at ten major stations (see Pollard et al., 2007) numbered M1 to M10. The following observations/sampling were conducted at each station where possible:

• Several CTD casts sampling:
  • Iron (using a titanium rig)
  • ²³⁴Th
  • Physical parameters (temperature, salinity etc)
  • Oxygen
  • CO₂
  • Nutrients using a stainless steel rig including a Lowered Acoustic Doppler Current Profiller (LADCP)
• At each thorium cast there was an associated Stand Alone Pump System (SAPS) deployment
• At some stations, a drifting PELAGRA trap was deployed for the duration of the work
• Megacoring was undertaken at M5 and M6
• Gravity coring was undertaken at M5, M6 and M10
• Longhurst Hardy Plankton Recorder (LPHR) tows were undertaken at a few major stations

For each of the major stations (M1 to M10), the following were determined:

• Primary productivity
• New Production
• Phytoplankton community composition
• Bacterial activity
• Iron
• Nutrient drawdown
• Thorium export

Sampling between major stations included:

• SeaSoar runs instrumented with:
  • CTD
  • Optical Plankton Counter (OPC)
  • Fast Repetition Rate fluorimeter (FRRf)
• Physics CTD casts on several lines
• Argo float deployments
• Zooplankton nets at nearly every CTD and major station
• Underway and on-station CO₂ measurements
• Underway nutrients and radium sampling
• 5 to 6 day ship-board iron-addition incubation experiments
• Checks against near-real-time satellite and model data
• Mooring deployments based on the satellite imagery in support of the CROZET (Benthic CROZEX) project.

The CROZEX cruises included 6 extra days in support of the CROZET (Benthic CROZEX) project, whose main cruise took place one year after the CROZEX cruises. The CROZET work undertaken during the CROZEX cruises was primarily the moored sediment trap deployments, although some of the coring work is applicable to both projects.

CROZEX produced significant findings in several disciplines, including confirmation that iron from Crozet fertilised the bloom and that phytoplankton production rates and most export flux estimates were much larger in the bloom area than the HNLC area (Pollard et al. 2007). Many of the project results are presented in a special CROZEX issue of Deep-Sea Research II (volume 54, 2007).

References

Pollard R., Sanders R., Lucas M. and Statham P., 2007. The Crozet natural iron bloom and export experiment (CROZEX). Deep-Sea Research II, 54, 1905-1914.

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for D286_CTD_15620

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: