HBIs and sterols in zooplankton Nansen Legacy Q3

Study Extent

Nansen Legacy main transect along 34°E in the Northern Barents Sea and adjacent Arctic Basin from 76 to 82°N

Sampling

Samples of 23 zooplankton taxa including copepods, krill, amphipods, pteropods and gelatinous species were collected at six stations (P1, P2, P4, P5, P6, P7), using MIK nets (1200 μm with 500 μm cod end) and WP3 net (1000 μm) for large taxa, Macroplankton trawl for mostly Thysanoessa spp. (multiple mesh sizes along the net, tapering to 8 mm at its end), Bongo net (180 μm) and Multinet (180 μm) for copepods (all species), and WP2 net (90 μm) for small copepods. Samples were sorted into the lowest possible taxonomic level, and/or stage/size groups (where possible) onboard the ship and immediately frozen at -80 ºC.

Method steps

1. HBIs and sterols were analysed at the University of Plymouth, UK. All samples were freeze-dried (-45 °C, 0.1 mbar, 24-48 h). Total lipids were extracted with chloroform/methanol (2:1, v/v) and cleaned with potassium chloride (0.88 %). Thereafter, samples were saponified with 20 % potassium hydroxide in water/methanol (1:9, v/v) at 70 °C for 1 h. Non-saponifiable lipids were extracted with hexane and purified by open column chromatography filled with SiO2. HBIs were eluted using hexane. The partially purified non-polar lipids containing HBIs were analysed by gas chromatography-mass spectrometry (GC-MS). Quantification of HBIs was achieved by integrating individual ion responses in single-ion monitoring mode, and normalising these to the corresponding peak area of the internal standard and an instrumental response factor obtained from purified standards (Belt et al., 2012). Sterols were eluted from the same silica column using hexane:methylacetate (4:1,v/v). Sterol fractions were derivatised using N,O-bis(trimethylsilyl)trifluoroacetamide (70 °C, 1 h) and analysed GC-MS. Individual sterols were identified by comparison of the mass spectra of their trimethylsilyl-ethers with published data (Belt et al., 2018). Belt, S.T., Brown, T.A., Sanz, P.C., and Rodriguez, A.N. (2012). Structural confirmation of the sea ice biomarker IP25 found in Arctic marine sediments. Environ. Chem. Lett. 10(2), 189-192 Belt, S.T., Brown, T.A., Smik, L., Assmy, P., and Mundy, C.J. (2018). Sterol identification in floating Arctic sea ice algal aggregates and the Antarctic sea ice diatom Berkeleya adeliensis. Org. Geochem. 118, 1-3

Copepods, krill, amphipods, pteropods, cnidarians, ctenophores, chaetognaths, appendicularians

1. Calanus glacialis
2. Calanus hyperboreus
3. Calanus finmarchicus
4. Metridia longa
5. Microcalanus spp.
6. Pseudocalanus spp.
7. Oithona similis
8. Paraeuchaeta norvegica
9. Meganyctiphanes norvegica
10. Thysanoessa inermis
11. Thysanoessa spp.
12. Themisto abyssorum
13. Themisto libellula
14. Clione limacina
15. Limacina helicina
16. Bougainvillia superciliaris
17. Catablema vesicarium
18. Beroe cucumis
19. Mertensia ovum
20. Eukrohnia hamata
21. Parasagitta elegans
22. Sagitta maxima
23. Oikopleura vanhoeffeni

Nansen Legacy main transect along 34°E in the Northern Barents Sea and adjacent Arctic Basin from 76 to 82°N