Artemev G.M.1,2*, Zalota A.K.2, Zakharov D.V.3, Mikhina A.S.4, Zaytseva K.A.4, Batalin G.A.5, Gareev B.I.5, Mingazov G.Z.5, Sabirov R.M.1†, Golikov A.V.6 2025. Nitrogen stable isotope composition suggests trophic differentiation in three chaetognath species (Parasagitta elegans, Pseudosagitta maxima, and Eukrohnia hamata) from the Barents Sea // Invert. Zool. Vol.22. No.4. P.614–630 [in English].
1 Department of Zoology, Kazan Federal University, Kremlyovskaya Street 18, Kazan 420008 Russia.
2 Shirshov Institute of Oceanology, Russian Academy of Sciences, Nakhimovskiy Prospekt 36, Moscow 117997 Russia.
3 Zoological Institute, Russian Academy of Sciences, Universitetskaya emb. 1, Saint Petersburg 199034 Russia.
4 Polar Branch of FSBSI “VNIRO” (“PINRO” named after N.M. Knipovich), Akademika Knipovicha Street 6, Murmansk 183038 Russia.
5 Institute of Geology and Petroleum Technologies, Kazan Federal University, Kremlyovskaya Street 4/5, Kazan, 420111 Russia.
6 GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstraße 1-3, Kiel, 24148 Germany.
* Corresponding author
Gleb Artemev: glebaartemjew@gmail.com ORCID https://orcid.org/0000-0003-4784-246X
Anna Zalota: azalota@gmail.com ORCID https://orcid.org/0000-0001-5590-5673
Denis Zakharov: zakharden@yandex.ru ORCID https://orcid.org/0000-0002-0885-3249
Anna Mikhina: annaorlova@pinro.vniro.ru ORCID https://orcid.org/0009-0008-8138-7396
Ksenia Zaytseva: annaorlova@pinro.vniro.ru ORCID https://orcid.org/0009-0006-7417-3803
Georgii Batalin: g@batalin.com ORCID https://orcid.org/0000-0001-7763-2389
Bulat Gareev: bulat@gareev.net ORCID https://orcid.org/0000-0002-7346-3722
Gazinur Mingazov: gazikovsky@gmail.com ORCID https://orcid.org/0000-0003-4012-334X
Rushan Sabirov: rushan.sabirov@mail.ru ORCID https://orcid.org/0000-0001-5204-3027
Alexey Golikov: golikov.ksu@gmail.com ORCID https://orcid.org/0000-0002-1596-2857
doi: 10.15298/invertzool.22.4.07
ABSTRACT: Chaetognaths are often considered strict predators, feeding primarily on copepods, but recent studies have shown that algae and/or marine snow may also be potential food source for some species in polar waters. The aim of this study was to investigate the relative trophic position (TP) of three chaetognath species (Parasagitta elegans, Pseudosagitta maxima, and Eukrohnia hamata) using nitrogen stable isotope analysis. Chaetognaths were collected at 14 stations in the Barents Sea during the polar nights in 2013 and 2014. Since natural variations of δ15N values can be expected across the stations, we used filter-feeding copepods (Calanus spp.) as an isotopic baseline. To assess the possible effect of size on the TPs of chaetognaths, we measured all specimens and analyzed them individually. Our results showed significant differences in δ15N values among the three species, indicating that P. elegans occupied the highest TP, followed by P. maxima and E. hamata. The variations of δ15N values across the stations were positively correlated with those of copepods in P. elegans, but not in the other two species. In E. hamata, we have detected negative correlation of δ15N values with depth, but it remains unknown if this trend is due to an isotopic shift in the food source or to actual changes in TP. Size was not a good predictor of TPs in these chaetognaths, as no general pattern in δ15N values was observed among the three species or within a single species. Our results complement other studies suggesting that E. hamata and P. maxima are omnivorous and feed at lower trophic levels than P. elegans. Thus, considering chaetognaths as a single trophic group may oversimplify their actual role in marine food webs.
KEY WORDS: Chaetognaths, Copepods, stable isotopes, trophic position, Polar night, Barents Sea.
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