DataSheet_1_DNA metabarcoding reveals a diverse, omnivorous diet of Arctic amphipods during the polar night, with jellyfish and fish as major prey.pdf

IntroductionCurrently, Arctic marine ecosystems are witnessing the most rapid physical changes worldwide, leading to shifts in pelagic and benthic communities and food web structure, concomitant with the introduction of boreal species. Gelatinous zooplankton or jellyfish represent one particular group of which several boreal species are prone to undergo significant poleward range expansions and population increases in the Arctic in the course of the ongoing changes. Historically, jellyfish were considered a trophic dead-end, but an increasing number of studies using modern tools have highlighted their role as major prey items in marine food webs. In this study, we aimed to verify the role of jellyfish and other metazoans as food sources in the Arctic polar night food web, when pelagic resources are limited.MethodsWe identified the diet of different bentho-pelagic amphipod species in the Atlantifying Kongsfjorden (West Svalbard) during the polar night. We regularly sampled lysianassoid and gammarid amphipods using baited traps and hand nets over a period of one month during the polar night and identified their diet spectrum by applying DNA metabarcoding (COI) to their stomach contents.ResultsWe demonstrate that all investigated species are omnivorous. Fish species including polar cod and snailfish, likely in the shape of carrion, played an important role in the diet of the scavengers Orchomenella minuta and Anonyx sarsi. Predation and potential scavenging on jellyfish contributed to the diet of all four investigated species, particularly for the species Gammarus setosus and G. oceanicus, as evidenced by high read abundances and high frequencies of occurrence. Besides jellyfish, crustaceans and macroalgae were important components of the diet of the two Gammarus species.DiscussionThe diverse jellyfish community present in Kongsfjorden in the polar night is clearly being utilized as a food source, either through pelagic feeding or feeding on jelly-falls, albeit to a different extent in the local amphipod community. These findings provide novel insights into the Arctic food web during the polar night and represent the first evidence of feeding on natural (non-experimental) jelly-falls.</p

Statistical parsimony haplotype networks based on the 16S rDNA sequences of <i>Eurythenes gryllus</i>.

<p>The dataset includes sequences from this study, that of France and Kocher <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone.0074218-France2" target="_blank">[12]</a> and Escobar-Briones <i>et al. </i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone.0074218-EscobarBriones1" target="_blank">[36]</a>. The area of each circle is proportional to the frequency of the haplotype in our sampling (a scale is presented). Each line represents a single substitution, nodes represent hypothetical haplotypes and colors refer to the sampling localities. Haplotype networks (95% probability threshold) are numbered (Eg1–9) according to the different clusters identified in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone-0074218-g002" target="_blank">Figures 2</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone-0074218-g003" target="_blank">3</a>.</p

Tree constructions on the three-gene dataset.

<p>Bayesian (BI) and Maximum Parsimony (MP) trees inferred for specimens of <i>Eurythenes gryllus</i> sampled in this study, based on the combined dataset of three genes (COI, 16S rDNA, 28S rDNA), showing posterior probabilities (>0.5) and bootstrap values (>50%; number of bootstrap replicates = 2,000), respectively. Two bootstrap values are shown at each node, the upper one represents the value when gaps were treated as fifth characters whilst the lower one represents the value when gaps were treated as missing data. The different clusters are assigned with the codes Eg1–5. For each cluster, distributional ranges (ocean basin, bathyal vs. abyssal, depth) are indicated. The colored squares refer to the sample localities of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone-0074218-g001" target="_blank">Figure 1</a>.</p

Sample localities of <i>Eurythenes gryllus sensu lato</i>.

<p>Abbreviations refer to samples from this study, that of France and Kocher <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone.0074218-France2" target="_blank">[12]</a> and Escobar-Briones <i>et al. </i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone.0074218-EscobarBriones1" target="_blank">[36]</a> (for details see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone-0074218-t001" target="_blank">Table 1</a>). The sampling region in the Southern Ocean is shown as an enlargement. Color codes are provided for each sampling locality and are used consistently in the other figures.</p

Bayesian tree inferred for the 16S rDNA dataset of <i>Eurythenes gryllus</i>.

<p>Posterior probabilities (>0.5) are shown at each node. In the case of identical sequences, all specimens are listed with corresponding abbreviations. For the sequences retrieved from GenBank <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone.0074218-France2" target="_blank">[12]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone.0074218-EscobarBriones1" target="_blank">[36]</a>, the accession number of the haplotype as well as the number of specimens per haplotype is indicated (when higher than 1). The different clusters are assigned with the codes Eg1–9. For each cluster, distributional ranges (ocean basin, bathyal vs. abyssal, depth) are indicated.</p

Results of the GMYC species delimitation test for <i>Eurythenes gryllus sensu lato</i> on the 16S dataset using single and multiple threshold methods.

<p>Statistical probabilities **P<0.01 and ***P<<0.0001.</p

Data of specimens of <i>Eurythenes gryllus sensu lato</i> (EG) and <i>Eurythenes</i> sp. (ES) obtained for this study and available on GenBank from France and Kocher [12] and Escobar-Briones <i>et al.</i>[36].

<p>For the specimens sequenced by France and Kocher <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone.0074218-France2" target="_blank">[12]</a>, the number of specimens is added between parentheses. Abbreviations: n.d. – no data, BT – baited traps, FT – fish traps.</p

Range and mean of pairwise K2P intraclade and interclade distances for COI, 28S rDNA and 16S rDNA for each clade identified within <i>Eurythenes gryllus</i> (sequence data from this study, France and Kocher [12], Escobar-Briones <i>et al.</i>[36]).

<p>Range and mean of pairwise K2P intraclade and interclade distances for COI, 28S rDNA and 16S rDNA for each clade identified within <i>Eurythenes gryllus</i> (sequence data from this study, France and Kocher <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone.0074218-France2" target="_blank">[12]</a>, Escobar-Briones <i>et al.</i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074218#pone.0074218-EscobarBriones1" target="_blank">[36]</a>).</p

Case 2 of Table 1.

<p>The set of species under focus is monophyletic but contains an internal subpart that is secondarily « exported » outside the area of reference (red circle). See text for discussion.</p

Three situations for the taxon of reference (columns) are to be considered: it is monophyletic, paraphyletic or polyphyletic.

<p>There are also three situations to consider for the components of this taxon in the given area of reference (lines): monophyletic, paraphyletic or polyphyletic. To explain the table, we consider again the example of the non-notothenioid fish family Liparidae. It is monophyletic as a family (first column), however its components of the Antarctic shelf are polyphyletic because they are each related to Arctic liparids (bottom line). So the Antarctic liparid situation is the bottom left cell. Case 2 (when a taxon originating in the area of reference secondarily “exports” a part of its descent outside this area, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068787#pone-0068787-g004" target="_blank">Fig. 4</a>) is discussed in the text.</p