References of "Lepoint, Gilles"
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See detailProgenesis as an intrinsic factor of ecological opportunity in a polyphenic amphibian
Lejeune, Benjamin ULiege; Bissey, Lucie; Didaskalou, Emilie et al

in Functional Ecology (in press)

1. Paedomorphosis, a developmental heterochrony involving the retention of larval traits at the adult stage, is considered a major evolutionary process because it can generate phenotypic variation without ... [more ▼]

1. Paedomorphosis, a developmental heterochrony involving the retention of larval traits at the adult stage, is considered a major evolutionary process because it can generate phenotypic variation without requiring genetic modifications. Two main processes underlie paedomorphosis: neoteny, a slowdown of somatic development, and progenesis, a precocious maturation associated to body size reduction. Being essentially a truncation of ontogeny, progenesis has often been deemed an evolutionary dead-end with advantages attributed to precocious reproduction or small body size required in specific environmental contexts (e.g. parasitism, interstitial life), but there is a lack of studies on the immediate ecological consequences of progenesis. 2. Because body size is a key factor determining trophic ecology in animals, we hypothesized that progenesis might intrinsically promote ecological opportunity via body size reduction (i.e. ‘the trophic advantage of progenesis’ hypothesis). We tested this hypothesis in facultatively progenetic palmate newts (Lissotriton helveticus) using stable isotope niche modelling and diet reconstruction in conjunction with traditional stomach content analyses and body condition assessment. 3. We show that not only did progenetic individuals occupy a different trophic niche than metamorphic individuals in all populations, but the smaller they were compared to metamorphs due to progenesis, the more different they were in terms of trophic ecology, with no negative effect on their body condition. 4. Altogether, the results suggest that via body size reduction, progenesis may generally act as an intrinsic factor of ecological opportunity, allowing the use of existing but previously unavailable resources, even in habitats where seemingly little opportunity exists. We argue that beyond the classically recognized fitness advantages of progenetic development, this process may also generally bring an immediate trophic advantage via body size reduction, which would have important implications to understand the evolution and adaptiveness of this process in many different taxa, from marine meiofauna to primates. [less ▲]

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See detailHabitat and resource segregation of two sympatric seals in the North Sea
Damseaux, France ULiege; Siebert, Ursula; Pomeroy, Patrick et al

in Science of the Total Environment (in press)

In the North Sea, sympatric grey and harbour seals may compete for food resources impacted by intense fishing activities and a recent increase of seal populations. In order to reduce inter-specific ... [more ▼]

In the North Sea, sympatric grey and harbour seals may compete for food resources impacted by intense fishing activities and a recent increase of seal populations. In order to reduce inter-specific competition, sympatric species must segregate at least one aspect of their ecological niches: temporal, spatial or resource segregation. Using isotopes and Se and Hg concentrations, the foraging resources of grey seals and harbour seals and the potential competition between these species in the North Sea was studied. δ13C, δ15N and δ34S values were combined with the concentrations of Hg and Se in blood samples of harbour and grey seals from the North Sea. Blood samples were collected on 45 grey seals and 37 harbour seals sampled along German and Scottish coasts. This multi-tracer approach showed spatial and resource partitioning within grey and harbour seals. Data indicated the offshore foraging distribution of grey seals as reflected by the lower δ15N values and T-Hg concentrations and higher Se concentrations, and the inshore foraging distribution of harbour seals because of higher δ15N values and T-Hg concentrations and lower Se concentrations. The SIAR mixing model revealed a more selective diet of grey seals compared to harbour seals, and the importance of sandeels in grey seal diet reflected by their high δ34S values. Lastly, diet ellipse overlaps between grey seals and harbour seals sampled along the German coasts suggested a potential sharing of food resources, possibly due to the increase number of grey seals number in this area during the foraging season - all year except breeding and moulting periods. The multi-tracer approach provided a more robust discrimination among diet resources and spatial foraging distributions of grey seals and harbour seals in the North Sea. [less ▲]

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See detailBioaccumulation of Per- and polyfluoroalkyl substances (PFASs) in a tropical estuarine food web
Miranda, Daniele A.; Benskin, Jonathan P.; Awad, Raed et al

in Science of The Total Environment (2021), 754

The biomagnification of per- and polyfluoroalkyl substances (PFASs) was investigated in a tropical mangrove food web from an estuary in Bahia, Brazil. Samples of 44 organisms (21 taxa), along with biofilm ... [more ▼]

The biomagnification of per- and polyfluoroalkyl substances (PFASs) was investigated in a tropical mangrove food web from an estuary in Bahia, Brazil. Samples of 44 organisms (21 taxa), along with biofilm, leaves, sediment and suspended particulate matter were analyzed. Sum (∑) PFAS concentrations in biota samples were dominated by perfluorooctane sulfonate (PFOS, 93% detection frequency in tissues; 0.05 to 1.97 ng g−1 ww whole-body (wb)), followed by perfluorotridecanoate (PFTrDA, 57%; 0.01 to 0.28 ng g−1 ww wb). PFOS precursors such as perfluorooctane sulfonamide (FOSA, 54%; 0.01 to 0.32 ng g−1 ww wb) and N-ethyl perfluorooctane sulfonamide (EtFOSA; 30%; 0.01 to 0.21 ng g−1 ww wb) were also detected. PFAS accumulation profiles revealed different routes of exposure among bivalve, crustacean and fish groups. Statistics for left-censored data were used in order to minimize bias on trophic magnification factors (TMFs) calculations. TMFs >1 were observed for PFOS (linear + branched isomers), EtFOSA (linear + branched isomers), and perfluorononanoate (PFNA), and in all cases, dissimilar accumulation patterns were observed among different trophic positions. The apparent biodilution of some long-chain PFCAs through the food chain (TMF < 1) may be due to exposure from multiple PFAS sources. This is the first study investigating bioaccumulation of PFASs in a tropical food web and provides new insight on the behavior of this ubiquitous class of contaminants. [less ▲]

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See detailDeepIso - a global open database of stable isotope ratios and elemental contents for deep-sea ecosystems.
Michel, Loïc ULiege; Bell, James; Dubois, Stanislas et al

Textual, factual or bibliographical database (2020)

The use of stable isotopes as ecological tracers in deep-sea ecosystems has a long history, dating back to the late 1970’s. Stable isotopes have been instrumental to many key-findings about ecosystem ... [more ▼]

The use of stable isotopes as ecological tracers in deep-sea ecosystems has a long history, dating back to the late 1970’s. Stable isotopes have been instrumental to many key-findings about ecosystem functioning, particularly in chemosynthesis-based habitats (hydrothermal vents, cold seeps). However, constraining sampling logistics commonly limit the scope, extent, and therefore insights drawn from isotope-based deep-sea studies. Overall, much is left to discover about factors globally influencing food web structure in deep-sea ecosystems. In this context, deep-sea ecologists have to ensure that no sample is left unexploited, and that all generated data are easily discoverable, available and reusable. DeepIso is a collaborative effort to produce a global compilation of stable isotope ratios and elemental contents in organisms from deep-sea ecosystems. In doing so, it aims to provide the deep-sea community with an open data analysis tool that can be used in the context of future ecological research, and to help deep-sea researchers to use stable isotope markers at their full efficiency. More info about the project can be found at https://loicnmichel.com/deepiso/ As of v1 (2020/10/22), the database contains 15 distinct datasets, for a total of 18677 fully documented measurements. Archived parameters currently include δ13C (n = 4587), δ15N (n = 4388), δ34S (n = 951), %C (n = 2740), %N (n = 2741), %S (n = 752) and C/N ratio (n = 2518). Those measurements pertain to 4378 distinct samples belonging to 493 taxa, plus sediments, suspended particulate organic matter, plankton and detritus. Samples were taken between 1989 and 2018 in multiple environments (hydrothermal vents, cold seeps, cold water coral reefs, and other benthic or pelagic environments) and at depths ranging up to 5209 meters. The database consists of three files: one containing the data itself, one describing all used terms (measurements or metadata, derived from Darwin Core standards, https://dwc.tdwg.org/terms/), and a changelog detailing changes made between successive versions. [less ▲]

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See detailTemporal trends of legacy organochlorines in different white-tailed eagle (Haliaeetus albicilla) subpopulations: A retrospective investigation using archived feathers
Sun, Jiachen; Covaci, Adrian; Bustnes, Jan Ove et al

in Environment International (2020), 138

Understanding the spatiotemporal patterns of legacy organochlorines (OCs) is often difficult because monitoring practices differ among studies, fragmented study periods, and unaccounted confounding by ... [more ▼]

Understanding the spatiotemporal patterns of legacy organochlorines (OCs) is often difficult because monitoring practices differ among studies, fragmented study periods, and unaccounted confounding by ecological variables. We therefore reconstructed long-term (1939–2015) and large-scale (West Greenland, Norway, and central Sweden) trends of major legacy OCs using white-tailed eagle (Haliaeetus albicilla) body feathers, to understand the exposure dynamics in regions with different contamination sources and concentrations, as well as the effectiveness of legislations. We included dietary proxies (δ13C and δ15N) in temporal trend models to control for potential dietary plasticity. Consistent with the hypothesised high local pollution sources, levels of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs) in the Swedish subpopulation exceeded those in the other subpopulations. In contrast, chlordanes (CHLs) and hexachlorobenzene (HCB) showed higher concentrations in Greenland, suggesting the importance of long-range transport. The models showed significantly decreasing trends for all OCs in Sweden in 1968–2011 except for CHLs, which only decreased since the 1980s. Nevertheless, median concentrations of DDTs and PCBs remained elevated in the Swedish subpopulation throughout the 1970s, suggesting that the decreases only commenced after the implementation of regulations during the 1970s. We observed significant trends of increasing concentrations of PCBs, CHLs and HCB in Norway from the 1930s to the 1970s/1980s and decreasing concentrations thereafter. All OC concentrations, except those of PCBs were generally significantly decreasing in the Greenland subpopulation in 1985-2013. All three subpopulations showed generally increasing proportions of the more persistent compounds (CB 153, p.p′-DDE and β-HCH) and decreasing proportions of the less persistent ones (CB 52, p.p′-DDT, α- and γ-HCH). Declining trends of OC concentrations may imply the decreasing influence of legacy OCs in these subpopulations. Finally, our results demonstrate the usefulness of archived museum feathers in retrospective monitoring of spatiotemporal trends of legacy OCs using birds of prey as sentinels. [less ▲]

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See detailA 15-Month Survey of Dimethylsulfoniopropionate and Dimethylsulfoxide Content in Posidonia oceanica
Richir, Jonathan ULiege; Champenois, Willy ULiege; Engels, Guyliann et al

in Frontiers in Ecology and Evolution (2020), 7(510), 1-15

Posidonia oceanica is the only reported seagrass to produce significant amount of dimethylsulfoniopropionate (DMSP). It is also the largest known producer of DMSP among coastal and inter-tidal higher ... [more ▼]

Posidonia oceanica is the only reported seagrass to produce significant amount of dimethylsulfoniopropionate (DMSP). It is also the largest known producer of DMSP among coastal and inter-tidal higher plants. Here, we studied (i) the weekly to seasonal variability and the depth variability of DMSP and its related compound dimethylsulfoxide (DMSO) in P. oceanica leaves of a non-disturbed meadow in Corsica, France, (ii) the weekly to seasonal variability and the depth variability of DMSP to DMSO concentration to assess the potential of the DMSP:DMSO ratio as indicator of stress, and (iii) the relationships between DMSP, DMSO, and the DMSP:DMSO ratio with potential explanatory variables such as light, temperature, photosynthetic activity (effective quantum yield of photosystem II), and leaf size. The overall average concentrations of organosulfured compounds in P. oceanica leaves were 130 ± 39 μmol.g−1fw for DMSP and 4.9 ± 2.1 μmol.g−1fw for DMSO. Concentrations of DMSP and DMSO in P. oceanica were overall distinctly higher and exhibited a wider range of variations than other marine primary producers such as Spartina alterniflora, phytoplankton communities, epilithic Cyanobacteria and macroalgae. Concentrations of both DMSP and DMSO in P. oceanica leaves decreased from a maximum in autumn to a minimum in summer; they changed little with depth. Potential explanatory variables except the leaf size, i.e., the leaf age were little or not related to measured concentrations. To explain the seasonal pattern of decreasing concentrations with leaf aging, we hypothesized two putative protection functions of DMSP in young leaves: antioxidant against reactive oxygen species and predator-deterrent. The similar variation of the two molecule concentrations over time and with depth suggested that DMSO content in P. oceanica leaves results from oxidation of DMSP. The DMSP:DMSO ratio remained constant around a mean value of 29.2 ± 9.0 μmol:μmol for the non-disturbed harvested meadow regardless of the time of the year, the depth or the leaf size. As suggested for the salt march plant S. alterniflora, we hypothesized the DMSP:DMSO ratio could be considered as indicator of stress in seagrasses exposed to environmental or anthropogenic stressors. More research would now be needed to confirm the functions of DMSP and DMSO in seagrasses and how the DMSP:DMSO ratio will vary under various disturbances. [less ▲]

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See detailEffects of preservation methodology on stable isotope compositions of sea stars
Le Bourg, Baptiste ULiege; Lepoint, Gilles ULiege; Michel, Loïc ULiege

in Rapid Communications in Mass Spectrometry (2020), 34(2), 8589

Rationale:Stable isotope analysis is used to investigate the trophic ecology of organisms and, in order to use samples from archived collections, and it is important to know whether preservation methods ... [more ▼]

Rationale:Stable isotope analysis is used to investigate the trophic ecology of organisms and, in order to use samples from archived collections, and it is important to know whether preservation methods alter the results. This study investigates the long-term effects of four preservation methods on sea stars isotopic composition and isotopic niche parameters.Methods:We assessed effects of preservation method (freezing, drying, formaldehyde, ethanol) and duration (0, 1, 3, 6, 9, 12 and 24 months) on the stable isotope ratios of carbon, nitrogen and sulfur of sea star tissues. Isotopic ratios were measured using CF-EA-IRMS. We also monitored the evolution ofcommonly used ecological metrics (isotopic niche parameters) throughout the experiment. Results:Clear changes of δ13C values were observed for samples stored in formaldehyde and ethanol. None of the preservation methods had significant or consistent effects on δ15Nvalues. Formaldehydeinduced a decrease of δ34S values. All these changes could be mitigated using correction factors.Isotopic niches parameters slightly changed over time when computed with δ13C and δ15N values, but inconsistent variations occurred when computed with δ13C and δ34S values.Conclusions: Overall, these results show that preservation may affect the stable isotope ratios of sea stars. Correction factors can be used to mitigate the effects of the preservation method on stable isotope ratios. Isotopic niches parameters are overall unchanged. Consequently, in most cases, museum samples are suitable to calculate isotopic niche parameters. [less ▲]

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See detailTotal tin (TSn) biomagnification: Evaluating organotin trophic flow and dispersion using hepatic TSn concentrations and stable isotope (C, N) data of nektonic organisms from Brazil
Dorneles, Paulo Renato ULiege; Schilithz, Priscila; de C. Paiva, Thais et al

in Marine Environmental Research (2020), 161

A previous investigation of our research team has demonstrated the suitability of using hepatic total tin (ΣSn) concentrations for evaluating dolphin exposure to organotins (OTs). The present study ... [more ▼]

A previous investigation of our research team has demonstrated the suitability of using hepatic total tin (ΣSn) concentrations for evaluating dolphin exposure to organotins (OTs). The present study develops the previous technique into three different approaches that comprise data: (1) on hepatic ΣSn concentrations of 121 Guiana dolphins (Sotalia guianensis) from five different coastal areas (CAs): (2) on ΣSn, δ13C and δ15N for 40 dolphins from Rio de Janeiro state (RJ), including ten different delphinid species; as well as (3) on hepatic ΣSn concentrations and δ15N values on 31 individuals from five different fish species from Sepetiba Bay (SB, Rio de Janeiro-RJ, Brazil). Hepatic ΣSn concentrations of Guiana dolphins from Guanabara Bay (GB, RJ) were significantly higher than those found in other four CAs from S and SE Brazilian regions. Significant positive correlations were found between ΣSn concentrations and δ13C data in delphinid species, demonstrating a coast-ocean gradient in dolphin exposure to OTs in RJ state. Significant and positive correlations were observed between ΣSn concentrations and both δ15N and Trophic Position (TP) values of fish, as well as high values were found for Trophic Magnification Factor (TMF = 3.03) and Trophic Magnification Slope (TMS = 0.14), demonstrating OT biomagnification in SB ichthyofauna. [less ▲]

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See detailDeep-water Zostera marina meadows in the Mediterranean
Boutahar, Loubna; Espinosa, Free; Richir, Jonathan ULiege et al

in Aquatic Botany (2020), 166

In Morocco, Zostera marina Linnaeus has disappeared from many localities where it was historically reported. The only known remaining meadows along Mediterranean coasts of Morocco, though in North Africa ... [more ▼]

In Morocco, Zostera marina Linnaeus has disappeared from many localities where it was historically reported. The only known remaining meadows along Mediterranean coasts of Morocco, though in North Africa, are those of Belyounech bay and Oued El Mersa bay, in the marine area of ‘Jbel Moussa’. An in-depth knowledge of these meadows is required for their effective conservation purpose. The Z. marina meadows of Jbel Moussa are deep, the lower limit being 17 m depth with patches extending down to 20 m depth. Seagrass cover of Belyounech bay meadow is continuous whereas that of Oued El Mersa is fragmented. Shoot density and aboveground biomass are higher in Belyounech meadow, with 745 ± 183 shoots.m−2 and 273 ± 40 gDW. m−2 of leaf biomass. During the survey, trawling scars and the invasive algae Caulerpa cylindracea Sonder were observed. Bioavailable Ni, As, Mo, Ag, Cd, Sn, Sb and U measured in the sediment are mainly accumulated in Z. marina roots. Nitrogen level is high in seagrass leaves and low in the sediment. Conversely, sediment is more enriched in phosphorus. Carbon levels and its isotopic ratio value are respectively higher and less negative in leaves when compared to the seagrass belowground compartments. All together, data collected during this survey allows defining the overall good health status of Z. marina meadows of Jbel Moussa. These Moroccan meadows, localized within the warm temperate-southern limit of the species, are well developed compared to many places worldwide. The exceptional presence of deep Z. marina meadows in the Mediterranean requires the implementation of measures as a major priority to ensure the conservation of these ecosystems, since seagrasses are being deeply threatened worldwide. [less ▲]

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See detailPosidonia oceanica, a top producer of dimethylsulfoniopropionate and dimethylsulfoxide
Richir, Jonathan ULiege; Champenois, Willy ULiege; Engels, Guyliann et al

in CIESM WORKSHOP MONOGRAPHS (2019, October 10)

We studied the dynamic of dimethylsulfoniopropionate and its derivative dimethylsulfoxide in Posidonia oceanica. The annual average concentrations in leaves were 129 ± 39 μmol.g for DMSP and 5.0 ± 2.1 ... [more ▼]

We studied the dynamic of dimethylsulfoniopropionate and its derivative dimethylsulfoxide in Posidonia oceanica. The annual average concentrations in leaves were 129 ± 39 μmol.g for DMSP and 5.0 ± 2.1 μmol.g for DMSO. DMSP and DMSO concentrations decreased from a maximum in the fall to a minimum in the summer and were mainly correlated to the seagrass leaf size. The similar variation of the two molecule concentrations suggested that DMSO content results from oxidation of DMSP. The DMSP:DMSO ratio, considered as indicator of stress in Spartina alterniflora, remained constant around a mean value of 27.7 μmol:μmol. More research is now needed to investigate the functions of DMSP and DMSO in seagrasses, how the DMSP:DMSO ratio will vary under disturbance and whether it is useful as indicator of stress. [less ▲]

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See detailProgenesis as an intrinsic factor of ecological opportunity in newts
Lejeune, Benjamin ULiege; Bissey, Lucie; Didaskalou, Emilia A et al

Conference (2019, September 03)

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See detailEstimating the actual biodiversity and evolutionary history of the amphipod genus Eusirus in the Southern Ocean
Salabao, Louraine ULiege; Frederich, Bruno ULiege; Lepoint, Gilles ULiege et al

Poster (2019, August 27)

The diversity of the Antarctic marine fauna has been shaped by various evolutionary processes (dispersals, diversifications, extinctions), which were greatly influenced by the geological and climatic ... [more ▼]

The diversity of the Antarctic marine fauna has been shaped by various evolutionary processes (dispersals, diversifications, extinctions), which were greatly influenced by the geological and climatic history of the region. Some Antarctic lineages are descendants of Gondwanan ancestors and arose by vicariance during the progressive breakup of Gondwana, which ultimately led to the complete geographical isolation of the Antarctic continent. The Plio-Pleistocene glacial cycles have been inferred to act as a “diversity pump” on the Antarctic continental shelf. Allopatric speciation of less dispersive organisms could have resulted from the isolation of populations in ice-free refugia during the glacial advances. These glacial cycles were often suggested to have influenced the diversification of numerous complexes of closely related and morphologically very similar Antarctic species. The continuous discovery of such (pseudo-) cryptic species in the Southern Ocean suggests that its biodiversity is currently greatly underestimated. Such species complexes have been found in the amphipod genus Eusirus. In a preliminary phylogeny (COI and 28S) of the whole genus, some Antarctic nominal Eusirus species are composed of genetically distant clades, suggesting putative new species. In this study, we will sequence complete mitochondrial genomes, using a combination of skim sequencing and long-range PCRs of different Eusirus species, to which sequence data from nuclear (28S, ITS2) will be added. By greatly increasing character sampling as well as taxon sampling (including Antarctic and non-Antarctic species) compared to preliminary studies, we intend to reconstruct a robust phylogeny of the genus. Based on this DNA dataset and the phylogeny, we aim to (1) provide a better estimate of the actual diversity within the genus, using various DNA-based species delimitation methods (GMYC, PTP, 4 theta rule and ABDG) and; (2) provide a better understanding of their evolutionary history: where does the Antarctic clade come from? Did Eusirus species disperse in and/or out of the Antarctic shelf at any time of their evolutionary history? Were there periods of increased diversification during their evolution on the shelf and how do these relate to the geological/glacial history of the region? [less ▲]

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See detailSpatial trophic plasticity of two dominant seagrass-associated fishes in Toliara lagoon (SW Madagascar)
Ravelohasina, Helga; Rasolofonirina, Richard; Henitsoa, Jaonalison et al

Poster (2019, July 01)

In the seagrass zone of Toliara (South West of Madagascar), the local fishermen deployed seine nets with small mesh size that likely affect the structure of seagrass meadow systems and associated fishes ... [more ▼]

In the seagrass zone of Toliara (South West of Madagascar), the local fishermen deployed seine nets with small mesh size that likely affect the structure of seagrass meadow systems and associated fishes. Nevertheless, the responses of fish communities living in this ecosystem to these threats are currently unknown for the WIO region. This present study aims to evaluate the trophic diversity of fishes living in seagrass beds and to assess their trophic plasticity. More specifically, along this work, we compare the diet of two dominant species (the rabbitfish Siganus sutor and the goby Oplopomus oplopomus) found in the catches of local fishermen on seagrass beds and we evaluate a potential variation in their trophic ecology. The sampling of fishes was achieved by collecting the catches of traditional fishermen using bottom seine nets. Fish sampling occurred in front of the Ankilibe fisherman village in December 2017 and 2018, and in front of the village of Sarodrano (December 2018). This sampling strategy allowed us to make spatial and temporal comparisons. In order to assess the diet of these two fish species, stomach content analyses was performed on 40 specimens/species/village/year. Using a binocular microscope, animal preys were identified to the level of class and assigned to the planktonic or the benthic compartment. Plant items are classified as either phytoplankton, fragments of algae, or seagrasses. The trophic niche of each fish populations was quantified in two ways: as a percentage of occurrence and as a mean percent composition of each item in the gut content. The rabbitfish has gut filled by 50% of detritus, 40% of fragments of seagrass, and 10% of phytoplankton. The diet of the goby was more diversified and composed of 40% of detritus, 25% of copepods, 20% of operculum, 10% of gastropods and 5% of ostracods. There was no significant difference between the two sites along the two years of campaign. An isotopic analyses will be effectuated soon to know the trophic position of the studied fishes. [less ▲]

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See detailThe dark side of the black caiman: Shedding light on species dietary ecology and movement in Agami Pond, French Guiana
Caut, Stephane; Francois, Vincent; Bacques, Matthieu et al

in PLoS ONE (2019), 14(6), 0217239

The black caiman is one of the largest neotropical top predators, which means that it could play a structuring role within swamp ecosystems. However, because of the difficulties inherent to studying black ... [more ▼]

The black caiman is one of the largest neotropical top predators, which means that it could play a structuring role within swamp ecosystems. However, because of the difficulties inherent to studying black caimans, data are sorely lacking on many aspects of their general biology, natural history, and ecology, especially in French Guiana. We conducted a detailed study of the Agami Pond black caiman population using a multidisciplinary approach. The aim was to better understand the species’ dietary ecology and movements in the pond, and thus its functional role in pond system. We gathered natural history data, tracked caiman movements using satellite transmitters, and characterized feeding ecology via stable isotope analysis. Our study was carried out over three sampling periods and spanned both wet and dry seasons, which differ in their hydrological and ecological conditions. Our results show that black caiman abundance and age demographics differed between seasons in Agami Pond. In the dry season, Agami Pond is one of the only areas within the marsh to hold water. It thus contains large quantities of different fish species, which form the basis of the black caiman’s diet. Caiman body size, a proxy for age class, was around 1.5 meters. During the wet season, which corresponds to the breeding period for migratory birds (e.g., Agami herons), adult black caimans are present in Agami Pond. Adults were most abundant in the inundated forest. There, most individuals measured up to 2 meters. They also exhibited a particular “predatory” behavior near bird nests, preying on fallen chicks and adults. Juveniles and subadults were present during both seasons in the pond’s open waters. These behavioral observations were backed up by stable isotope analysis, which revealed ontogenetic variation in the caiman’s isotopic values. This isotopic variation reflected variation in diet that likely reduced intraspecific competition between adults and young. The telemetry and microchip data show that different age classes had different movement patterns and that seasonal variation in the pond may influence caiman prey availability and reproductive behavior. The new information gathered should help predict this species’ responses to potential ecosystem disturbance (e.g., water pollution, habitat destruction) and inform the development of an effective conservation plan that involves locals and wildlife officials. [less ▲]

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See detailIncreased sea ice cover alters food web structure in East Antarctica
Michel, Loïc ULiege; Danis, Bruno; Dubois, Philippe et al

in Scientific Reports (2019), 9

In recent years, sea ice cover along coasts of East Antarctica has tended to increase. To understand ecological implications of these environmental changes, we studied benthic food web structure on the ... [more ▼]

In recent years, sea ice cover along coasts of East Antarctica has tended to increase. To understand ecological implications of these environmental changes, we studied benthic food web structure on the coasts of Adélie Land during an event of unusually high sea ice cover (i.e. two successive austral summers without seasonal breakup). We used integrative trophic markers (stable isotope ratios of carbon, nitrogen and sulfur) to build ecological models and explored feeding habits of macroinvertebrates. In total, 28 taxa spanning most present animal groups and functional guilds were investigated. Our results indicate that the absence of seasonal sea ice breakup deeply influenced benthic food webs. Sympagic algae dominated the diet of many key consumers, and the trophic levels of invertebrates were low, suggesting omnivore consumers did not rely much on predation and/or scavenging. Our results provide insights about how Antarctic benthic consumers, which typically live in an extremely stable environment, might adapt their feeding habits in response to sudden changes in environmental conditions and trophic resource availability. They also show that local and/or global trends of sea ice increase in Antarctica have the potential to cause drastic changes in food web structure, and therefore to impact benthic communities. [less ▲]

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See detailEvolutionary processes that shaped the diversity of the amphipod genus Eusirus in the Southern Ocean
Salabao, Louraine ULiege; Frederich, Bruno ULiege; Lepoint, Gilles ULiege et al

Conference (2019, May 20)

Various evolutionary processes greatly influenced by the geological and climatic history shaped the diversity of the current Antarctic marine fauna. In the past, these Antarctic species have survived ... [more ▼]

Various evolutionary processes greatly influenced by the geological and climatic history shaped the diversity of the current Antarctic marine fauna. In the past, these Antarctic species have survived different glacial cycles through dispersal to refugia, and/or adaptations to novel abiotic and biotic conditions. With the increasing temperatures in the polar regions, marine fauna is currently faced with three possible outcomes: adaptation, migration or extinction. Based on how these organisms were able to survive environmental changes in the past will allow us to predict their future response. In this study, amphipods of the genus Eusirus are as model organisms as knowledge on their ecology and biogeography is still very limited. The evolutionary history of Eusirus amphipods is phylogenetically reconstructed through time with molecular data. DNA sequence data are obtained by sequencing the complete mitochondrial genomes, using a combination of skimming sequencing and long-range PCRs amplicons of different Eusirus species. Mitochondrial data will be complemented with additional sequence data from nuclear genes. Time-calibrated phylogenies will be used as basis for plotting ecological and trophic data generated by stable isotope analyses as well as morphological information. By combining data from time-calibrated phylogenies as well as from ecology and morphology, we aim to understand the evolutionary processes that led to the current diversity of Eusirus amphipods. [less ▲]

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See detailEnvironmental drivers of sea stars feeding ecology in the Southern Ocean
Le Bourg, Baptiste ULiege; Blanchard, Alice; Danis, Bruno et al

Conference (2019, May 06)

The Antarctic continent and the surrounding Southern Ocean undergo strong and contrasted impacts of climate change. In the Western Antarctic Peninsula, sea ice cover and ice season duration are decreasing ... [more ▼]

The Antarctic continent and the surrounding Southern Ocean undergo strong and contrasted impacts of climate change. In the Western Antarctic Peninsula, sea ice cover and ice season duration are decreasing, presumably in relation with increased air and water temperature and northwesterly winds originating from the also warming subtropical Pacific. In contrast, despite increased air and deep water temperatures, sea ice cover and ice season duration are increasing in other Antarctic regions. This is possibly linked with ocean stratification due to freshwater inputs from the melting continental ice. These changes are likely to impact marine communities and food webs of the Southern Ocean. Sea stars (Echinoderms: Asteroidea) are an important group of the Southern Ocean benthos. Compared to other organisms, they seem to have relatively high physiological tolerance to warming. However, they could be indirectly affected by climate change, notably through quantitative and qualitative modifications of food availability. In this context, the aim of this study was to infer the trophic diversity of sea stars of the Southern Ocean to assess their potential trophic plasticity regarding food web changes. Thanks to collaborative networking and valorization of museum samples, Sea stars samples taken in summer in various regions around the Antarctic continent with different types of environment (Antarctic or Subantarctic, deep-sea or coastal, presence of sea ice or not) were obtained. Stable isotopes ratios of C (denoted δ13C) and N (denoted δ15N) were then analysed in the tegument of sea stars in order to investigate their trophic ecology. Isotopic niches metrics were also computed to assess differences of trophic diversity between regions. Variability in stable isotope ratios and isotopic niche metrics revealed strong differences in sea star feeding ecology between and within locations, possibly in relation with differences in environmental conditions, notably sea ice coverage and dynamics. For example, on the continental shelf of Antarctic South Shetland Islands, small isotopic niches could indicate that sea stars exploit a food web based on a common basal food source and exhibit a "trophic continuum". In this context, absence of sea ice before and during the sampling period could have limited the number of available food sources. By contrast, on the continental shelf of the Antarctic Marguerite Bay or in the Subantarctic South Georgia Island, sea stars had large isotopic niches that suggest that they could exploit one or several food webs based on more than one food source, and exhibited strong trophic segregation. In Marguerite Bay, this could be linked with progressive sea ice melting, which allows export of both sea ice materials and blooming phytoplankton to the benthic compartment. In South Georgia, on the other hand, oligotrophic conditions and thus reduced availability of phytoplankton are more likely to explain this pattern. Ultimately, this project helps us understanding which ecological processes determine how an ecologically important animal group copes with environmental modifications linked to climate change. This research was funded by the Belgian Federal Science Policy Office (BELSPO) in the framework of the vERSO  and RECTO project (rectoversoprojects.be). [less ▲]

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See detailRefugia and ecosystem tolerance in the Southern Ocean - the RECTO project
Schön, Isa; Christiansen, Henrik; Danis, Bruno et al

Conference (2019, May)

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See detailUnravelling the evolutionary processes that shaped the diversity of the amphipod genus Eusirus in the Southern Ocean
Salabao, Louraine ULiege; Frederich, Bruno ULiege; Lepoint, Gilles ULiege et al

Poster (2019, May)

Various evolutionary processes greatly influenced by the geological and climatic history shaped the diversity of the current Antarctic marine fauna. In the past, these Antarctic species have survived ... [more ▼]

Various evolutionary processes greatly influenced by the geological and climatic history shaped the diversity of the current Antarctic marine fauna. In the past, these Antarctic species have survived different glacial cycles through dispersal to refugia, and/or adaptations to novel abiotic and biotic conditions. With the increasing temperatures in the polar regions, marine fauna is currently faced with three possible outcomes: adaptation, migration or extinction. Based on how these organisms were able to survive environmental changes in the past will allow us to predict their future response. In this study, amphipods of the genus Eusirus are as model organisms as knowledge on their ecology and biogeography is still very limited. The evolutionary history of Eusirus amphipods is phylogenetically reconstructed through time with molecular data. DNA sequence data are obtained by sequencing the complete mitochondrial genomes, using a combination of skimming sequencing and long-range PCRs amplicons of different Eusirus species. Mitochondrial data will be complemented with additional sequence data from nuclear genes. Time-calibrated phylogenies will be used as basis for plotting ecological and trophic data generated by stable isotope analyses as well as morphological information. By combining data from time-calibrated phylogenies as well as from ecology and morphology, we aim to understand the evolutionary processes that led to the current diversity of Eusirus amphipods. [less ▲]

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Peer Reviewed
See detail‘Homemade’: the phenotypic diversity of coral reef damselfish populations is driven by the local environment
Chen, Chia-Ting; Robitzch, Vanessa; Sturaro, Nicolas ULiege et al

in Biological Journal of the Linnean Society (2019), 127

Documenting phenotypic variation among populations is crucial for our understanding of micro-evolutionary processes. To date, the quantification of trophic and morphological variation among populations of ... [more ▼]

Documenting phenotypic variation among populations is crucial for our understanding of micro-evolutionary processes. To date, the quantification of trophic and morphological variation among populations of coral reef fish at multiple geographical scales remains limited. This study aimed to quantify diet and body shape variation among four populations of the damselfish Dascyllus abudafur living in different environmental conditions from the central Red Sea and from Madagascar. Stomach content analyses showed that one adaptive response of D. abudafur inhabiting turbid waters is a trophic shift from almost exclusive zooplanktivory to a diet consisting of planktonic and benthic prey. Our morphometric data reveal differences in cephalic profile and body shape among populations, in agreement with this variation in trophic strategy. Isotopic diversity and body shape disparity vary among populations and we thus demonstrate that coral reef fish populations are not equal in terms of phenotypic diversity among sites and regions. Finally, our comparative analysis reveals that the main axes of body shape variation among populations are shared at both small (Red Sea sites) and large (Madagascar and Red Sea sites) spatial scales. This study raises new questions about the factors governing the direction of response to selection in this fish species. [less ▲]

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