Spatial and Temporal Variability of Ice Algal Trophic Markers—With Recommendations about Their Application

Leu, Eva; Brown, Thomas A.; Graeve, Martín; Wiktor, Józef; Hoppe, Clara Jule Marie; Chierici, Melissa; Fransson, Agneta; Verbiest, Sander; Kvernvik, Ane C; Greenacre, Michael

doi:10.3390/jmse8090676

Cited by 31 publications

(26 citation statements)

References 61 publications

(102 reference statements)

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“…This finding is in agreement with an earlier study from the Nansen Basin when both firstyear and multi-year ice were studied (Kohlbach et al 2016: δ 13 C FA iPOM: −28.4 to −23.4 ‰; δ 13 C FA pPOM: −39.3 to −26.4 ‰) and with a study of seasonal firstyear ice in the Bering Sea (Wang et al 2014: δ 13 C FA iPOM: −26.5 to −21.0 ‰; δ 13 C FA pPOM: −30.4 to −27.0 ‰). Leu et al (2020) found an increasing trend in δ 13 C FA values in a seasonally sea-ice-covered fjord in Svalbard throughout spring (April−May), suggesting that bloom succession and an increase in underice light play a role in these values, similar to seasonal changes determined by bulk δ 13 C values. To date, studies investigating δ 13 C FA values of individual fatty acids in POM throughout the Arctic are not as ubiquitous compared to studies of bulk δ 13 C POM.…”

Section: δ 13 C Differences In Biomarker Fatty Acids Between Habitatssupporting

confidence: 61%

“…To date, studies investigating δ 13 C FA values of individual fatty acids in POM throughout the Arctic are not as ubiquitous compared to studies of bulk δ 13 C POM. Isotopic enrichment in bulk δ 13 C values in iPOM over pPOM is seasonally and regionally variable, depending on environmental and physiological factors in addition to taxonomic community composition and biomass, which can be minimal or absent at times (de la Vega et al 2019, Leu et al 2020.…”

Section: δ 13 C Differences In Biomarker Fatty Acids Between Habitatsmentioning

confidence: 99%

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Ice-algal carbon supports harp and ringed seal diets in the European Arctic: evidence from fatty acid and stable isotope markers

Kunisch

Graeve

Gradinger

et al. 2021

Mar. Ecol. Prog. Ser.

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Sea-ice declines in the European Arctic have led to substantial changes in marine food webs. To better understand the biological implications of these changes, we quantified the contributions of ice-associated and pelagic carbon sources to the diets of Arctic harp and ringed seals using compound-specific stable isotope ratios of fatty acids in specific primary producer biomarkers derived from sea-ice algae and phytoplankton. Comparison of fatty acid patterns between these 2 seal species indicated clear dietary separation, while the compound-specific stable isotope ratios of the same fatty acids showed partial overlap. These findings suggest that harp and ringed seals target different prey sources, yet their prey rely on ice and pelagic primary production in similar ways. From Bayesian stable isotope mixing models, we estimated that relative contributions of sympagic and pelagic carbon in seal blubber was an average of 69% and 31% for harp seals, and 72% and 28% for ringed seals, respectively. The similarity in the Bayesian estimations also indicates overlapping carbon sourcing by these 2 species. Our findings demonstrate that the seasonal ice-associated carbon pathway contributes substantially to the diets of both harp and ringed seals.

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Section: δ 13 C Differences In Biomarker Fatty Acids Between Habitatssupporting

confidence: 61%

Section: δ 13 C Differences In Biomarker Fatty Acids Between Habitatsmentioning

confidence: 99%

Ice-algal carbon supports harp and ringed seal diets in the European Arctic: evidence from fatty acid and stable isotope markers

Kunisch

Graeve

Gradinger

et al. 2021

Mar. Ecol. Prog. Ser.

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show abstract

“…In contrast, sterols yield less specific dietary information, but can be used to distinguish, to some extent, phytoplankton-produced versus animal-produced carbon (Drazen et al, 2008;Ruess and Müller-Navarra, 2019). Each of these biochemical methods has strengths and weaknesses, but when applied in combination they yield different facets to feeding and are a powerful approach to study food webs (Leu et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Multiple Trophic Markers Trace Dietary Carbon Sources in Barents Sea Zooplankton During Late Summer

et al. 2021

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We investigated diets of 24 Barents Sea zooplankton taxa to understand pelagic food-web processes during late summer, including the importance of sea ice algae-produced carbon. This was achieved by combining insights derived from multiple and complementary trophic marker approaches to construct individual aspects of feeding. Specifically, we determined proportions of algal-produced fatty acids (FAs) to reflect the reliance on diatom- versus dinoflagellate-derived carbon, highly branched isoprenoid (HBI) lipids that distinguish between ice-associated and pelagic carbon sources, and sterols to indicate the degree of carnivory. Copepods had the strongest diatom signal based on FAs, while a lack of sea ice algae-associated HBIs (IP25, IPSO25) suggested that they fed on pelagic rather than ice-associated diatoms. The amphipod Themisto libellula and the ctenophores Beroë cucumis and Mertensia ovum had a higher contribution of dinoflagellate-produced FAs. There was a high degree of carnivory in this food web, as indicated by the FA carnivory index 18:1(n−9)/18:1(n−7) (mean value < 1 only in the pteropod Clione limacina), the presence of copepod-associated FAs in most of the taxa, and the absence of algal-produced HBIs in small copepod taxa, such as Oithona similis and Pseudocalanus spp. The coherence between concentrations of HBIs and phytosterols within individuals suggested that phytosterols provide a good additional indication for algal ingestion. Sea ice algae-associated HBIs were detected in six zooplankton species (occurring in krill, amphipods, pteropods, and appendicularians), indicating an overall low to moderate contribution of ice-associated carbon from late-summer sea ice to pelagic consumption. The unexpected occurrence of ice-derived HBIs in pteropods and appendicularians, however, suggests an importance of sedimenting ice-derived material at least for filter feeders within the water column at this time of year.

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“…A similar seasonal change from pelagic to sympagic carbon source composition could be expected for Arctic crustaceans, provided they feed to some extent throughout the winter and can actually access the ice-associated carbon. Preferred dietary sources of marine animals and their seasonality can be elucidated from the composition of lipidbased trophic markers (Leu et al, 2020). Their stability when transferred along the marine food chain makes them valuable trophic proxies in disentangling food-web relationships and revealing the importance of varying carbon sources (e.g., Scott et al, 1999;Iverson, 2009).…”

Section: Introductionmentioning

confidence: 99%

Winter Carnivory and Diapause Counteract the Reliance on Ice Algae by Barents Sea Zooplankton

et al. 2021

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The Barents Sea is a hotspot for environmental change due to its rapid warming, and information on dietary preferences of zooplankton is crucial to better understand the impacts of these changes on food-web dynamics. We combined lipid-based trophic marker approaches, namely analysis of fatty acids (FAs), highly branched isoprenoids (HBIs) and sterols, to compare late summer (August) and early winter (November/December) feeding of key Barents Sea zooplankters; the copepods Calanus glacialis, C. hyperboreus and C. finmarchicus and the amphipods Themisto libellula and T. abyssorum. Based on FAs, copepods showed a stronger reliance on a diatom-based diet. Phytosterols, produced mainly by diatoms, declined from summer to winter in C. glacialis and C. hyperboreus, indicating the strong direct linkage of their feeding to primary production. By contrast, C. finmarchicus showed evidence of year-round feeding, indicated by the higher winter carnivory FA ratios of 18:1(n-9)/18:1(n-7) than its larger congeners. This, plus differences in seasonal lipid dynamics, suggests varied overwintering strategies among the copepods; namely diapause in C. glacialis and C. hyperboreus and continued feeding activity in C. finmarchicus. Based on the absence of sea ice algae-associated HBIs (IP25 and IPSO25) in the three copepod species during both seasons, their carbon sources were likely primarily of pelagic origin. In both amphipods, increased FA carnivory ratios during winter indicated that they relied strongly on heterotrophic prey during the polar night. Both amphipod species contained sea ice algae-derived HBIs, present in broadly similar concentrations between species and seasons. Our results indicate that sea ice-derived carbon forms a supplementary food rather than a crucial dietary component for these two amphipod species in summer and winter, with carnivory potentially providing them with a degree of resilience to the rapid decline in Barents Sea (winter) sea-ice extent and thickness. The weak trophic link of both zooplankton taxa to sea ice-derived carbon in our study likely reflects the low abundance and quality of ice-associated carbon during late summer and the inaccessibility of algae trapped inside the ice during winter.

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Spatial and Temporal Variability of Ice Algal Trophic Markers—With Recommendations about Their Application

Cited by 31 publications

References 61 publications

Ice-algal carbon supports harp and ringed seal diets in the European Arctic: evidence from fatty acid and stable isotope markers

Ice-algal carbon supports harp and ringed seal diets in the European Arctic: evidence from fatty acid and stable isotope markers

Multiple Trophic Markers Trace Dietary Carbon Sources in Barents Sea Zooplankton During Late Summer

Winter Carnivory and Diapause Counteract the Reliance on Ice Algae by Barents Sea Zooplankton

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