AMT11 extracted chlorophyll-a measured fluormetrically from CTD bottle samples
Data Acquisition and Analysis
This data originates from analyses on samples collected from CTD rosette bottles for 22 CTD casts. Samples were collected from the second CTD each day at approximately 11:00 (local time). Water samples were taken at 8-9 depths with 10 litre Niskin bottles between 4 and 250 m (typically from above and below the 1% light irradiance depth and included samples from the subsurface chlorophyll maximum and at least three from across the thermocline).
A 250 ml sample from each depth was gently filtered through 0.2 µm glass fibre filters for the determination of total chlorophyll-a concentration. Each filter was extracted in 10 ml of 90% acetone for 24 hours in a -20 °C walk in freezer. Chlorophyll-a was measured on a 10-AU Turner Design digital fluorometer calibrated against a standard chlorophyll-a stock solution.
References Cited
Instrumentation Description
Not relevant to this dataset.
BODC Data Processing Procedures
Data were submitted to BODC in an Excel spreadsheet and accessioned under BODC archive PML040069. The sample metadata provided (Date, time (local and GMT), latitude, longitude and depth) were checked against information held in the database. There were two discrepancies - cast 1 all the depths provided were 5 m shallower than the bottle firing depths; cast 3 a sample was provided for depth 25m but no bottle was fired at this depth and the position of the data in the spreadsheet suggested a typo and the depth should have been 250 m.
Parameter codes defined in BODC parameter dictionary were assigned to the variable. The units supplied in the spreadsheet were µg l -1 , which were equivalent to the Parameter Dictionary units so no unit conversions were necessary.
Data loaded into BODC's database following BODC procedures.
A parameter mapping table is provided below;
Originator's Parameter | Units | Description | BODC Parameter Code | Units | Comments |
---|---|---|---|---|---|
[Chla] | µg l -1 | Concentration of chlorophyll-a {chl-a} per unit volume of the water body [particulate >GF/F phase] by filtration, acetone extraction and fluorometry | CPHLFLP1 | mg m -3 | n/a |
Data Quality Report
BODC were not advised of any data quality checks made by the data originator prior to submission of the dataset.
Problem Report
Not relevant to this dataset.