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Abstract:
This dataset contains results from water column samples collected during Kongsfjorden and Rijpfjorden (MOSJ and ICE cruises) from the years 2011 to 2020. All samples are collected from Niskin bottles from the CTD rosette of the ship. The data is from the transect from the glacier front to the Fram Strait in Kongsfjorden and from the inner glacier front in the inner part of the fjord across the shelf break.
Results include
Nutrients:
- Ammonium [mmol/m3]
- Nitrite (NO2) [mmol/m3]
- Nitrate (NO3) [mmol/m3]
- Phosphate (PO4) [mmol/m3]
- Silicate (SiO4) [mmol/m3]
- NH4 [mmol/m3]
Biogenic silica
- BSi (Si/SiOH4) [µg/L]
Chlorophyll
- chlorophyll a [mg/m3]
- phaeophytin [mg/m3]
Particulate Organic Carbon & Nitrogen (POC/PON)
- PON [µg/L]
- POC [µg/L]
- PON [µmol/L]
- POC [µmol/L]
Parameters from CTD bottle data (only from 2016)
- inSituTemperature [C]
- potentialTemperature [C]
- salinity [PSU]
Methods
Nutrients
Samples were filled directly from the Niskin bottle into new or acid-washed 20 ml scintillation vials and added with 0.2 ml (200 μl) of Triklormethan for spectrophotometry (Merck no. 2447.0500). The samples were stored in a fridge temperature. Samples for ammonium were also collected and analysed immediately on board, with the method of Solorzano (1969). The following nutrients; nitrite (NO2-), nitrate (NO3-), phosphate (PO43-) and silicate (SiO44-) are measured spectrophotometrically at 540, 540, 810 and 810 nm, respectively, on a modified Alpkem Flow Solution IV autoanalyzer or a modified Scalar autoanalyser (Bendschneider & Robinson 1952 RFA Methodology).
Measurement of nitrite
The method is based on that nitrite reacts colorimetrically with aromatic amin and forms a diazonium ion in acidic medium. The diazonium ion connects to a new aromatic amine and forms an azo. The absorption of the color is measured spectrophotometrically at 540 nm on a modified Alpkem Flow Solution IV autoanalyzer or a modified scalar autoanalyzer (Bendschneider & Robinson 1952 RFA Methodology). The detection limit for nitrites is 0.06 microM (Scalar) and 0.05 microM (Alpkem) and is significant to the second decimal place.
Measurement of nitrate
The method is based on the nitrate is reduced to nitrite (NO2-) by means of cadmium in the presence of copper ions. Then forming NO2- a diazonium ion with an aromatic amine in an acidic environment, which is diverted to a new aromatic amine and an azo dye is formed. Absorption of the color is measured spectrophotometrically at 540 nm on a modified Alpkem Flow Solution IV autoanalyser or a modified scalar autoanalyser (Bendschneider & Robinson 1952 RFA Methodology). The amount of nitrate is calculated as the difference between total reduced nitrite (this method) and NO2 measured without cadmium reduction (see Method U3_3 above). The detection limit for nitrate is 0.4 microM (Scalar) and 0.5 microM (Alpkem) and is significant to the first decimal place.
Measurement of phosphate (PO43-)
The method is based on the phosphate reacts with molybdate to form phosphomolybdate in acid medium (pH < 1) providing a yellow dye. This dye is reduced by ascorbic acid to a blue dye, and absorbance is measured spectrophotometrically at 810 nm on a modified Alpkem Flow Solution IV autoanalyzer or a modified Scalar autoanalyzer (Grashoff 1965). The detection limit for phosphate is 0.06 microM (Scalar and Alpkem) and is significant to the second decimal place.
Measurements of silicate
The method is based on the silicate reacts with molybdate to form a silikomolybdat (yellow dye) in an acidic environment (pH = 1.5-2). Oxalic acid is added to the silikomolybdat which then is reduced with ascorbic acid. The result is a blue compound which is measured spectrophotometrically at 810 nm on a modified Alpkem Flow Solution IV autoanalyser or a modified Scalar autoanalyzer (Grashoff 1965). The detection limit for silicate is 0.7 microM (Scalar) and 0.4 microM (Alpkem) and is significant to the first decimal place.
Chlorophyll
Chlorophyll samples were collected on 25-mm GF/F filters (Whatman), extracted in 100% methanol for 12 h at 5°C on board the ship and measured fluorometrically with an Trilogy Turner Fluorometer (Turner Design, Inc.). Phaeopigments were measured by fluorescence after acidification with 5% HCl. Calibration of the fluorometer was carried out following the JGOFS protocol 35 (Knap et al., 1996).
Data structure:
The data follows Darwin Core nomenclature as far as possible but also includes variables that aren’t supported by Darwin Core. The data includes event parameters and result parameters.
Event parameters:
- expedition: cruise number for R/V Kronprins Haakon
- eventDate: the date-time when an event occurred, using ISO 8601-1:2019 format (2020-07-27T07:16:03.446Z).
- locationID: station name
- decimalLongitude: geographic latitude (in decimal degrees, using the spatial reference system given in geodetic datum)
- decimalLatitude: geographic longitude (in decimal degrees, using the spatial reference system given in geodeticDatum)
- bottomDepthInMeters: bottom depth in meters
- fieldNumber: human-readable sample ID (e.g. ZNUT-001)eventRemarks: comments or remarks about the event (free text field)
- gearType: the gear used to take the sample e.g. MultiNet 200 µm
- samplingDepthInMeters: bottom depth of the sampled layer
Result parameters:
- PO4 [mmol/m3]: Concentration of phosphate as mmol per m3
- NO2 [mmol/m3]: Concentration of nitrite as mmol per m3
- NO3 [mmol/m3]: Concentration of nitrate as mmol per m3
- Si [mmol/m3]: Concentration of silicate as mmol per m3
- NH4 [mmol/m3]: Concentration of ammonium as mmol per m3
- BSi [µg/L]: Concentration of biogenic silica as µg per litre
- chlorophyll a [mg/m3]: Concentration of chlorophyll a as mmol per m3
- phaeophytin [mg/m3]: Concentration of phaeophytinas mmol per m3
- PON [µg/L]: Concentration of particulate organic nitrogen in µg per litre
- POC [µg/L]: : Concentration of particulate organic carbon in µg per litre
- PON [µmol/L]: Concentration of particulate organic nitrogen as µ mol per litre
- POC [µmol/L]: Concentration of particulate organic carbon as µ mol per litre
References
- Bendschneider, K. & Robinson, R.I. (1952), A new Spectrophotometric method for the determination of nitrite in Seawater. J. Mar. Res. 2: 87-96.
- Grasshoff, K. (1965), On the Automatic Determination of Phosphate, Silicate and Fluoride in Seawater. ICES Hydrographic Committee Report No. 129.
- Knap, A., Michaels, A., Close, A., Ducklow, H. & Dickson A. (1996), Measurement of Chlorophyll a and Phaeopigments by fluorometric analysis. JGOFS report 19: 118-122.
- RFA Methodology, Nitrate+nitrite Nitrogen, A303-S170 Revision 6-89. ALPKEM, a division of OI Analytical, College Station, Texas
- Solorzano, L. (1969), Determination of ammonia in natural waters by the phenolhypochlorite method. Limnol Oceanogr. 14:799.