Show more...
Abstract:
The data has been collected during a cruise with RV Lance from 30 July to 2 August 2017. Samples have been collected from in front of tidewater glaciers by use of MIK nets and baited traps.
The dataset contains stable isotope ratios as d13C (‰) and d15N (‰) and trophic level. For the fish species the stomach content, stomach content wet weight and the degree of filling are also recorded.
Quality
Sampling method:
Zooplankton and fish were collected from RV Lance using a Methot-Isaac-Kidd (MIK) ring net (3.15 m2 opening, 13-m long net with 1500 μm pore size and a 500 μm mesh in the last metre), fitted with a 10-L cod end. Benthic amphipods were collected with baited traps in strings of five traps each deployed overnight at different locations in the glacial bay outside Kronebreen.
Analyse method:
All samples have been analysed at Institute for Energy Technology (IFE) according to their standard procedure, described briefly here:
- Lipids and non-dietary carbon (i.e. carbonates) are removed from samples prior to analyses since lipids have a high turnover and are depleted in 13C relative to other body compounds. The removal of lipids will also reduce differences in stable isotope composition due to variations in body lipid content, and therefore make the C:N ratios more comparable among species.
- Lipids are removed by Soxhlet extraction with CH2Cl2 : 7% CH3OH for approx. 2h, washing with 2N HCl and distilled water to neutral pH. The samples are dried at 80°C for 12h, weighed and transferred into 9*15 mm tin capsules. Approximately 1 mg of the sample was used.
- The sample was combusted in the presence of O2 and CrO3 at 1700°C in a Eurovector element analyser. Reduction of NOx to N2 was done in Cu oven at 650 °C.
- H2O was removed in a chemical trap of KMnO4.
- N2 and CO2 were separated on a 2 m Poraplot Q GC column.
- The C/N ratio was quantified on basis of TCD results from the GC
- N2 and CO2 were directly injected on-line to Nu Instrument Horizon, Isotope Ration Mass Spectrometer for determination of δ13C and δ15N.
Accuracy & precision:
The accuracy and precision of δ13C and δ15N analyses are tested by replicate analysis of an internal standard (IFE trout) every 10 samples.
Presentation of results
Stable isotope ratios are expressed as the deviation from standards in ppt (‰) according to the following equation:
δX=[(R”sample” /Rstandard)*1000]
X = 13C or 15N and R = the corresponding ration 13C/12C or 15N/14N International standards, Pee Dee Belemnite for δ13C (PDB: USGS 24), and atmospheric air for δ 15N (IAEA-N-1 and 2,) were used to determine R standard.
Data structure:
The data is following Darwin Core nomenclature as far as possible but also includes variables that aren’t supported by Darwin Core. All information about the sampling such as eventDate, latitude, longitude, depts etc is located in event file while the result such as N, C etc. are found in the stable isotope file. The fieldNumber would be the link between the stable isotope and event files.
Header name index - events
- fieldNumber: sample ID (e.g. SI-044)
- expedition: cruise name
- eventDate: the date-time when an event occurred, using ISO 8601-1:2019 format (2020-07-27T07:16:03.446Z).
- area: the area groups used in the publication “Tidewater glaciers as “climate refugia” for zooplankton-dependent food web in Kongsfjorden, Svalbard”
- 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
- eventRemarks: comments or remarks about the event (free text field)
- gearType: the gear used to take the sample e.g. MultiNet 180 µm
- maximumDepthInMeters: bottom depth of the sampled layer
- minimumDepthInMeters: top depth of the sampled layer
- principalInvestigatorName: name of the person in charge of the sample collection
- principalInvestigatorEmail: email address of the person in charge of the sample collection
- principalInvestigatorInstitution: affiliated institution of the person in charge of the sample collection
Header name index – stable isotope
- scientificName: full scientific name of the identified organism at the lowest taxonomic level that can be ascertained.
- identificationQualifier: A standard term (sp., spp., and indet
- lifeStage: the age class, life stage, or life form/morph of the organism.
- sizeGroup: the size group in mm.
- tissue: the tissue of the sample used for stable isotope analysis
- d13C (‰): stable isotope ratios of carbon expressed as the deviation from standards in ppt (‰)
- d15N (‰): stable isotope ratios of nitrogen expressed as the deviation from standards in ppt (‰)
- trophicLevel: The trophic level of a consumer can be calculated as the difference between δ 15N and the food web baseline assuming a constant fractionation between trophic levels according to the following equation: TL= α+ (δ15 N consumer/δ15 Nbase)/∆N
- W% C: Dry Weight % Carbon
- W% N: Dry Weight % Nitrogen
- C/N ratio: The ration of carbon to nitrogen
- IFE Lab ID: ID used at Institute for Energy Technology (IFE) when analysing the samples The following terms are recorded only for fish samples:
- stomachContent: The species found in the stomach
- stomachContent_wetWeight (mg): The wet weight (mg) of the stomach content
- stomachFilling: The percentage filling of th estomach