French Research Institute for Exploitation of the Sea
ArchiMer - Institutional Archive of IfremerNot a member yet
27944 research outputs found
Sort by
Establishing Historical Baselines of Arthropod Assemblages Using Rodent Paleomiddens
No full textAimArthropods are under‐represented in paleoecological studies but are critical agents in ecological processes. Despite rigorous documentation of diverse arthropod assemblages from ancient rodent (or paleo) middens worldwide, their use for studying ancient arthropod diversity has stalled in recent decades. Here, we review published studies to identify how paleomidden arthropods can be leveraged to address significant questions in ecology and synthesise spatiotemporal trends in ancient arthropod diversity. LocationGlobal with a focus on the Americas. Time PeriodFrom ~40,000 to 100 years before present. Major Taxa StudiedFossil arthropods preserved in rodent paleomiddens. MethodsWe identified four primary objectives in ecology that can be advanced using paleomidden arthropod fossils: the reconstruction of ancient biodiversity, the elucidation of mechanisms and processes driving arthropod range shifts, the incorporation of arthropods into ancient trophic webs, and the assessment of adaptive responses to changing environments. ResultsWe identified 20 papers reporting arthropod remains, of which 14 provided data suitable for quantitative analyses. Although no significant differences in arthropod community diversity were found across broad geographic regions, substantial differences in community structure were observed. In North America, we also detected a decline in arthropod diversity from 10 to 5 ka BP, driven primarily by the absence of high‐diversity assemblages during this period. Main ConclusionsPaleomidden arthropods remain an underutilised ecological resource that can be leveraged to improve the inferential scope of arthropod research across spatiotemporal gradients. Collaboration between paleo‐ and neoecologists could help expand the sampling of ancient and modern arthropod communities, particularly those associated with paleomiddens, to create high‐resolution datasets spanning important periods in biogeographical history. Paleomidden arthropods will remain a fundamental component for understanding arthropod biodiversity changes in the past, present, and future
Mieux publier et sans se ruiner... Les sciences marines explorent le modèle épi-revue vs PCI
No full textUntangling the Primary Biotic and Abiotic Controls on Oxygen, Inorganic and Organic Carbon Isotope Signals in Modern Microbialites
No full textMicrobialites are organo‐sedimentary structures formed throughout most of the Earth history, over a wide range of geological contexts, and under a multitude of environmental conditions affecting their composition. The carbon and oxygen isotope records of carbonates, which are most often their main constituents, have been used as a widespread tool for paleoenvironmental reconstructions. However, the multiplicity of factors that influence microbialites formation is not always properly distinguished in their isotopic record, in both ancient and modern settings. It is therefore crucial to refine our understanding of the processes controlling microbialites isotopic signal. Here, we analyzed the carbon and oxygen isotope compositions from bulk and micro‐drilled carbonates as well as bulk organic carbon isotope compositions in microbialites from four Mexican volcanic crater lakes of increasing alkalinity. The survey of four lakes allows comparing microbialite formation processes and their geochemical record within distinct physico‐chemical contexts. The geochemical analyses were performed in parallel to petrographic and mineralogical characterization and interpreted in light of the known microbial community composition for microbialites of the same lakes. Combining these data, we show that the potential for isotopic biosignature preservation primarily depends on physico‐chemical conditions. Carbon isotope biosignatures pointing out to an autotrophic influence on carbonate precipitation are preserved in the lowest alkalinity lakes. By contrast, higher alkalinity lakes, where microbialites are more massive, favor carbonate precipitation in isotopic equilibrium with the lake water, with secondary influence of heterotrophic organic carbon degradation. From these results, we suggest that microbialite carbonate C isotope records can be interpreted as the balance between the microbialite net primary productivity and the amount of precipitation that relates to physico‐chemical forcing. The signals of microbialite oxygen isotope compositions highlight a lack of understanding in the oxygen isotope records of relatively rare carbonate phases such as hydromagnesite. Nonetheless, we show that these signals are primarily influenced by the basins' hydrology, though biological effects may also play a (minor) role. Overall, both carbon and oxygen isotopic signals may record a mixture of different local/global and biotic/abiotic phenomena, making microbialites intricate archives of their growth environment, which should thus be interpreted with cautions and in the light of their surrounding sediments
Benthic Food Resources and the Condition of Bentho-Demersal Fish: Spatial Trends and Relationships in the Bay of Biscay Northern Shelf
No full textLocated at the interface between the continent and the open ocean, continental shelves exhibit strong gradients in nutrients, organic matter, and primary production. Within these ecosystems, benthic invertebrates play a key role in transferring energy and matter from primary producers to bentho-demersal fish. Consequently, macrobenthic biomass can serve as an indicator of food resource availability for these species. This study focused on the northern part of the Bay of Biscay continental shelf to examine this relationship. Given the limited availability of field data, both empirical and biogeochemical models were employed to estimate macrobenthic biomass indices and to generate spatial distribution maps. Modeled biomass indices showed strong correlations with the few available field observations, although discrepancies were evident in deeper, poorly sampled areas. A pronounced coastal–offshore gradient was observed, with macrobenthic biomass decreasing towards offshore waters and locally elevated values occurring in deeper muddy sediments. Among the eight bentho-demersal fish species examined, the four identified as predominantly benthic-feeders exhibited positive relationships between body condition and macrobenthic biomass indices, particularly among smaller individuals. These findings suggest that modeled macrobenthic biomass indices and maps can serve as effective proxies for benthic resources gradients and provide insights into spatial variability in energy transfer within the food web. Nonetheless, improved field sampling, especially in deep circalittoral zones, remains essential to refine spatial trends, enhance our understanding of benthic food-web processes, and support the sustainable management of bentho-demersal fisheries
Carbon and Nitrogen Stable Isotopes Evidence High Trophic Segregation Within a Meso- to Bathypelagic Micronektonic Invertebrate Community From Canyons in the North-East Atlantic
No full textIn deep-pelagic ecosystems, the trophic ecology of micronektonic species (such as fish, jellyfish, krill, shrimps, and cephalopods) is largely overlooked, with most research focusing almost exclusively on fish. However, like fish, invertebrate organisms play key roles in food webs, both as consumers and as predators. Here, we aimed to provide an integrated overview of the relative trophic position, segregation, and overlap of all main groups of species constituting the deep-pelagic micronektonic community. Stable nitrogen (δ15N) and carbon (δ13C) isotope compositions have thus been measured in 13 species belonging to three groups (jellyfish, crustaceans, and cephalopods) sampled in the Bay of Biscay slope area (Northeast Atlantic), as proxies for trophic level and feeding habitat of species. The addition of published isotopic data from deep-pelagic fish sampled in the same zone also allowed the inclusion of vertebrates in the analyses of the trophic structure of the community. The invertebrate community exhibited wide ranges of δ15N and δ13C values (6.45‰ and 2.71‰, respectively). Cephalopods appeared to segregate along a continuum of δ15N values, with important differences between muscular and fast-swimming species (Histioteuthis reversa and Todarodes sagittatus) presenting higher δ15N values than gelatinous species (Teuthowenia megalops and Haliphron atlanticus). In contrast, crustaceans appeared to have lower δ15N values and to be more strongly segregated by δ13C values, suggesting different feeding habitats (range δ13C = 2.71‰). Some species showed more pelagic (13C-depleted) signatures (e.g., Meganyctiphanes norvegica) while others showed 13C-enriched values, possibly corresponding to a more benthopelagic diet (e.g., the two Pasiphaeidae species). Isotopic niche calculations at the group level revealed important overlaps between cephalopods and fish, as well as between jellyfish and crustaceans. These results are of significant importance for understanding the complex functioning of growing interest deep-pelagic food webs on slope areas, by promoting a multi-taxa approach
Digital Pcr (Dpcr) vs. Quantitative Pcr (Qpcr) Approaches for the Quantification of Two Perkinsus Species within Clam Tissue Samples
No full textThe parasite Perkinsus olseni (Perkinsea, Alveolata), the etiological agent of Perkinsosis, infects a wide range of bivalves and gastropods, including clams, particularly in Europe. This parasite coexists in sympatry with another Perkinsus species, P. chesapeaki, which, as opposed to P. olseni, has not been directly associated to mortality events. Accurate detection and quantification of Perkinsus infections, even at low infection intensities, are crucial for monitoring clam population health and assessing risks associated with emerging diseases. In this study, we compared molecular methodologies based on duplex real-time quantitative PCR (qPCR) and digital PCR (dPCR) in order to develop effective host resource management strategies. We first evaluated detection capabilities and the impact of potential inhibitors using both methodologies across varying DNA concentrations. Subsequently, we applied these methods to two contrasting French environments: Noirmoutier, characterized by low prevalence and infection intensity, and Arcachon Bay, which exhibits high prevalence and infection intensity. Our results demonstrate that dPCR should be prioritized for detecting and quantifying parasites at low infection intensities (101-102 cp.µL−1), as it minimizes false-negative results compared to qPCR. Notably, dPCR provided new insights and revealed cryptic infections, demonstrating greater efficiency in detecting P. chesapeaki in lightly infected sites such as Noirmoutier. Conversely, infection intensity was underestimated with dPCR relative to qPCR for clams with moderate to high Perkinsus infection levels (103 cp.µL−1 or higher), proving the latter more suitable for medium to heavily infected areas like Arcachon Bay. These findings are important as they represent the first in situ monitoring of both Perkinsus species using culture-free methodologies. This work provides essential tools for resource management and conservation strategies to address emerging diseases
Functional and phylogenomic approaches reveal novel types of M42 peptidases with contrasted enzymatic properties in Archaea
No full textM42 peptidases are half-megadalton aminopeptidases characterized by a tetrahedral architecture (TET) ubiquitous across all domains of life. Despite their widespread occurrence, their evolutionary history and functional diversity remain largely unexplored. Here we show an unsuspected and largely untapped wealth of archaeal TET peptidases, exhibiting remarkable functional heterogeneity, as illustrated by the characterization of six novel enzymes. Using structural biology, phylogeny, and enzymatic studies, we establish robust criteria for high-throughput identification of TET peptidases and perform the first systematic study of their genomic distribution and functional diversity across the archaeal kingdom. We propose an 11-group classification for these enzymes and identify one group as the ancestral lineage that first emerged in Archaea. By coupling taxonomic distribution patterns with functional insights, we highlight the presence of multiple TET enzymes with selective activities in heterotrophic and mixotrophic organisms, suggesting a role for TET peptidases in the degradation of environmental peptides. Overall, this work illuminates the underexplored diversity of TET enzymes, uncovering a complex evolutionary history linked to their potential biological function
Insights into mesoscale eddy dynamics: a three-dimensional perspective on potential density anomalies
No full textMesoscale eddies are fundamental components of global ocean circulation. In situ observations and Lagrangian analyses have shown that most eddies are materially coherent, transporting a water mass within their core that differs from the surrounding environment. Additionally, laboratory experiments indicate that eddies locally modify stratification in accordance with thermal wind balance, regardless of whether they trap a water mass. These two mechanisms drive, respectively, spiciness mode anomalies and heaving mode anomalies associated with mesoscale eddies. In this study, aiming to quantitatively assess the physical processes governing mesoscale eddy dynamics, we introduce a novel theoretical decomposition of the potential density field within eddy cores to account for both effects. This framework is applied to six anticyclonic eddies sampled during the EUREC4A-OA, METEOR 124, and Physindien 2011 oceanographic campaigns. Unlike previous studies, we evaluate not only the amplitude of these anomalies but also their vertical structure. Our results confirm that \textit{heaving mode anomalies} dominate the total density anomaly. However, in contrast to previous assumptions, we demonstrate that their vertical structure is dictated by the local background stratification and often follows a nearly Gaussian profile. Meanwhile, spiciness anomalies provide only a second-order contribution to the total potential density anomaly, rendering them negligible in most dynamical processes governing mesoscale eddies. By bridging experimental results with observational eddy datasets, this study refines our understanding of mesoscale eddy vertical structure, offering a more accurate predictive framework for their shape and role in oceanic property transport
A new promising anticancer agent: a glycosaminoglycan-mimetic derived from the marine bacterial infernan exopolysaccharide
No full textMarine microorganisms are a promising source of innovative compounds for medical applications. The present study aimed to investigate anticancer potential of oversulfated low molecular weight derivatives, named OSIDs, prepared from infernan, a marine bacterial exopolysaccharide. In order to identify a lead, OSIDs with different sulfate contents and molecular weights were firstly evaluated in vitro in a large series of human and murine tumor cell lines. Amongst all derivatives tested, OSID4 was the most effective, showing a significant dose-dependent inhibitory effect on the viability of cancer cells. OSID4 was then able to significantly slow down progression of lung and melanoma tumor growth in immunocompetent tumor-bearing mouse models. In immunodeficient mice bearing a human lung carcinoma, a notable inhibitory effect of OSID4, comparable to doxorubicin, was observed. In combination with doxorubicin, OSID4 did not exhibit any drug interaction. The activity of OSID4 was confirmed by its modulatory effect on the transcriptomic profile of human lung cancer cells. Finally, toxicity and pharmacokinetic parameters disclosed that OSID4 presented no toxicity and no bleeding risk. In conclusion, by combining its notable anticancer and moderate anticoagulant activities, OSID4 may be promising for treatment of cancers associated with a high risk of thromboembolic events
Contributions of biological and physical dynamics to deglacial CO2 release from the polar Southern Ocean
No full textAs a critical region regulating air-sea gas exchanges, the polar Southern Ocean has important implications for deglacial atmospheric CO2 rises. However, proxy data evidence is sparse to evaluate the respective roles of Southern Ocean biological and physical dynamics in affecting past air-sea CO2 exchanges due to longstanding challenges in obtaining carbonate materials to reconstruct surface conditions in this region. Here, we circumvent these challenges by constraining polar Southern Ocean surface-water conditions based on preformed deep-water properties derived from paired carbonate ion-phosphate-oxygenation reconstructions during the last deglaciation. We show that polar Southern Ocean carbon losses coincided with increased deep-ocean preformed nutrient concentrations, highlighting reduced biological carbon utilization as a key process for deglacial CO2 outgassing. By comparing total carbon losses with those attributable to biological processes, we further show that enhanced physically-driven air-sea gas exchanges in the polar Southern Ocean strongly drove CO2 outgassing towards the end of the last deglaciation