AMT16 CTD bottle sample measurements of Particulate Organic Carbon (POC) and Particulate Organic Nitrogen (PON)
Data Acquisition and Analysis
Water samples were collected from the five main light depths during the pre-dawn CTD cast using the Sea-Bird CTD rosette system. This resulted in 32 casts being sampled during the cruise. Samples (2-4 litres) were filtered on GF/F filters and frozen for analysis back in the UK. Once returned to the laboratory inorganic carbonates were removed from the filters by acidification with fuming concentrated hydrochloric acid. The filters were dried in a 60°C oven for 24 hrs, packaged in pre-combusted aluminium foil (Hilton et al., 1986) and analysed on a Thermo Finnegan flash EA122 elemental analyser (Poulton et al., 2007).
References Cited
Hilton J., Lishman J.P., Mackness S. and Heaney S.I., 1986. An automated method for the analysis of particulate carbon and nitrogen in natural waters. Hydrobiologica, 141, 269-271.
Poulton A.J., Adey T.R., Balch W.M. and Holligan P., 2007. Relating coccolithophore calcification rates to phytoplankton community dynamics: regional differences and implications for carbon export. Deep Sea Research Part II: Topical Studies in Oceanography, 54(5-7), 538-557.
Instrumentation Description
Not relevant for this dataset
BODC Data Processing Procedures
Data were submitted to BODC in a Microsoft Excel spreadsheet file (AMT_POC_data(BODC).xls) containing all the AMT phase 2 POC/PON CTD data. Sample metadata for AMT16 provided in the file (Date, CTD no, Lat, Long, Depth) were checked against information held in the database and the cruise report for the 32 CTD casts sampled - there was one discrepancy. There was no bottle fired at 32m on cast 52, there was however a bottle fired at 23m and it is likely there is a typo in the file supplied.
Parameter codes defined in BODC parameter dictionary were assigned to the variables. The data were provided in units which were equivalent to those used for the relevant parameters in the BODC database. No conversion was necessary. A parameter mapping table is provided below.
| Originator's Parameter | Units | Description | BODC Parameter Code | Units | Comments |
|---|---|---|---|---|---|
| POC | mmol C m -3 | Concentration of carbon (organic) {POC} per unit volume of the water column [particulate >GF/F phase] by filtration, acidification and elemental analysis | CORGCAP1 | µmol C l -1 | n/a |
| PON | mmol N m -3 | Concentration of nitrogen (total) {'PON'} per unit volume of the water column [particulate >GF/F phase] by filtration, acidification and elemental analysis | NTOTCAP1 | µmol N l -1 | n/a |
Data Quality Report
There were 12 samples where the data originator advised there were problems either with suspected leaks, brown specks or zooplankters on the filter or broken filters. The data from these samples has been flagged accordingly. In addition the 2 data points from cast 18 have been flagged as the data originator was not certain of the depths sampled.
Problem Report
Not relevant to this dataset.
