Mission Baelo Claudia. Rapport d'activités
(01/09/2026)
LIENSs, INSU - CNRS, ULR, CNRS, HALMA, CNRS, MC, IRAA, UL2, AMU, CNRS, HeRMA [Poitiers], UP, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
How annual course of photoperiod shapes seasonal behavior of diploid and triploid oysters, Crassostrea gigas
In this work, we study if ploidy (i.e. number of copies of chromosomes) in the oyster Crassostrea gigas may introduce differences in behavior and in its synchronization by the annual photoperiod. To answer to the question about the effect of the seasonal course of the photoperiod on the behavior of C. gigas according to its ploidy, we quantified valve activity by HFNI valvometry in situ for 1 year in both diploid and triploid oysters. Chronobiological analyses of daily, tidal and lunar rhythms were performed according the annual change of the photoperiod. In parallel, growth and gametogenesis status were measured and spawning events were detected by valvometry. The results showed that triploids had reduced gametogenesis, without spawning events, and approximately three times more growth than diploids. These differences in physiological efforts could explain the result that photoperiod (daylength and/or direction of daylength) differentially drives and modulates seasonal behavior of diploid and triploid oysters. Most differences were observed during long days (spring and summer), where triploids showed longer valve opening duration but lower opening amplitude, stronger daily rhythm and weaker tidal rhythm. During this period, diploids did major gametogenesis and spawning whereas triploids did maximal growth. Differences were also observed in terms of moonlight rhythmicity and neap-spring tidal cycle rhythmicity. We suggest that the seasonal change of photoperiod differentially synchronizes oyster behavior and biological rhythms according to physiological needs based on ploidy.
(PLoS ONE. vol. 12, n° 1932-6203, pp. e0185918, 01/09/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Benthic production, respiration and methane oxidation in Lobelia dortmanna lawns
Isoetid macrophytes such as Lobelia dortmanna and Littorella uniflora are engineering species with an extensive root system and high radial oxygen loss (ROL). Despite several studies on these macrophytes, the effect of their oxygenation on methane dynamics has never been investigated. In this study, we hypothesize that isoetids promote dissolved inorganic carbon (DIC) fixation and methane (CH4) oxidation in sandy sediments. Our whole-ecosystem approach study lasted two years (2013-2014) on two oligo-mesotrophic shallow lakes. Benthic chamber incubations confirmed that, as a result of primary production and methanotrophy, isoetid lawns had consistently lower benthic carbon fluxes than bare sediments. On a daily basis, vegetated areas acted as a carbon sink (-0.7 ± 0.4 g C m-2d-1, as DIC + CH4) whereas bare sediments acted as a net source (0.6 ± 0.5 g C m-2d-1, as DIC + CH4). Photosynthetic quotients of < 1 indicated that photosynthetically-produced oxygen was not released into the water column, but accumulated in leaf lacunae or was transferred to the rhizosphere, that contributing to the alteration of net benthic fluxes at the sediment-water interface. This preliminary study highlights the necessity of further investigating the role that isoetids play in mitigating greenhouse gas emissions from temperate shallow lakes.
(Hydrobiologia, n° 0018-8158, pp. 21-34, 01/09/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Post-depositional evolution over a time scale of 1 million years of eastern Mediterranean organic-rich and organic-poor sediments: new insights on the debromination and layer-silicate markers
Organic matter degradation is the engine behind the biogeochemical evolution of sediments during burial. Previous research has shown that eogenesis is the seat of a complex interplay between organic matter, microbes and the most reactive part of inorganic compounds, such as clay minerals. To explore the variability and stability of bromine and clay minerals as geochemical and mineral tracers, we selected an eastern Mediterranean core that has a high degree of stability in the quality and quantity of organic matter through time at a one-million-year scale and great variability in organic matter content at a 10 ky scale. According to the very low maximal burial depth reached by these sediments (the core length is only 36.5 m), physical parameters, such as temperature and pressure, did not significantly influence the evolution of the studied parameters during the burial history. The bulk clay mineralogy of organic-rich and organic-poor sediments is similar all along the investigated core material; smectite predominates over kaolinite. The only identified authigenic minerals are biogenetic framboidal pyrite and manganese oxides. The X-ray data and the chemical compositions of the smectite are characteristic of a montmorillonite which is representative of a detrital Nile source. At a one-million-year scale, the organic matter content has no significant influence on clay eogenesis, and detrital smectite and kaolinite remain unchanged. Bromine is present in marine organic matter as organobromine compounds. During eogenesis, bromine is released from organic matter as bromide ion, resulting in an increase in the bromide concentration in the pore water with depth. Dissolved bromide can be used as a conservative tracer of the debromination of sedimentary organic matter. For the first time, we established that solid-phase BrOrg is a reliable tracer of debromination rates in marine sediments. The rate of debromination depends on the organic matter content. The rate increases from less than 2.3 × 10−4 μmolBrOrg mol.C−1.y−1 to 6.3 × 10−4 μmolBrOrg mol.C−1.y−1 when TOC varies from 0.17 to 3%. This increase is related to the development of the bacterial population and provides the basis for further investigation of other oceanic basins. For TOC values >4%, the rate of debromination decreases. We propose that the bioavailability of organic matter is another factor of variability in the debromination rate.
(Bulletin de la Société Géologique de France. vol. 188, n° 0037-9409, pp. 21, 01/09/2026)
LUSAC, UNICAEN, NU, IC2MP [Poitiers], UP, INC-CNRS, CNRS, EMBS, iSTeP, UPMC, CNRS, ETH Zürich, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CINaM, AMU, CNRS
Migratory behavior, metabolism, oxidative stress and mercury concentrations in marine and estuarine European glass eels (Anguilla anguilla)
The relationships between the migratory behavior, methylmercury (MeHg) concentrations, oxidative stress response and detoxification processes were investigated in glass eels collected in marine (Molliets) and estuarine (Urt) waters (Adour estuary, South West France) at the end of the fishing season (April). Glass eel migratory behavior was investigated in an experimental flume according to their response to dusk. Fish responding to the decrease in light intensity by ascending in the water column and moving with or against the flow were considered as having a high propensity to migrate (migrant). Glass eels still sheltering at the end of the 24 h catching period were considered as having a low propensity to migrate and were called non-migrant. Our results provide some evidence that estuarine glass eels were bigger, presented a higher propensity to migrate and a lower oxidative stress response than marine glass eels. This might reflect a selection process, some marine glass eels progressively settling or dying before reaching Urt and/or a change in feeding behavior. In April, glass eels restart feeding in the Adour estuary which might decrease the oxidative stress possibly related to starvation, and enhance migration. MeHg concentrations was significantly higher in non-migrant than in migrant glass eels and it is suggested that non-migrant glass eels might present a higher vulnerability to stress (at least contamination and/or starvation), although the underlying mechanisms remain to be elucidated. © 2016 Elsevier Inc.
(Physiology & behavior. vol. 169, n° 0031-9384, pp. 33--40, 01/09/2026)
ECOBIOP, INRA, UPPA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPREM, UPPA, INC-CNRS, CNRS
Earthquake imprints on a lacustrine deltaic system: The Kürk Delta along the East Anatolian Fault (Turkey)
Deltas contain sedimentary records that are not only indicative of water-level changes, but also particularly sensitive to earthquake shaking typically resulting in soft-sediment-deformation structures. The Kürk lacustrine delta lies at the south-western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault, which has generated earthquakes of magnitude 7. This study re-evaluates water-level changes and earthquake shaking that have affected the Kürk Delta, combining geophysical data (seismic-reflection profiles and side-scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water-level changes provides a temporal framework for the depositional record. In addition to the common soft-sediment deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake-induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a palaeoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the East Anatolian Fault. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating ($^{137}$Cs and $^{210}$Pb), two major sedimentary events were attributed to the ad 1874 to 1875 East Anatolian Fault earthquake sequence. Their sedimentological characteristics were determined by X-ray imagery, X-ray diffraction, loss-on-ignition, grain-size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post-seismic sediment reworking of earthquake-triggered landslides.
(Sedimentology. vol. 64, n° 0037-0746, pp. 1322-1353, 01/09/2026)
ULiège, UGent, KAUST, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ITU
Signification environnementale de guano de salanganes et de chiroptères de Nouvelle-Calédonie. Premiers résultats
L'intérêt est grandissant pour le potentiel présenté par les acccumulations cavernicoles de guano de chauves-souris et d'oiseaux en tant qu'enregistrements stratigraphiques continentaux, complémentaires voire alternatifs aux archives étudiées générale-ment (sédiments lacustres, palustres, tourbeux, etc.). Ces dépôts permettent des reconstructions de la variabilité climatique à haute résolution pour des échelles de temps récentes à plus anciennes, grâce à la calibration de nouveaux proxies susceptibles d'enregistrer ces variations. Ainsi la comparaison du contenu pollinique et des traceurs isotopiques δ13 C et δD des n-alcanes du guano de différents animaux insectivores, les salanganes diurnes (Collocalia spodiopygia) et les chiroptères nocturnes (Micropterus robustior) cohabitant dans de nombreuses grottes de Nouvelle-Calédonie, met en évidence une grande variabilité. Celle-ci est à l'image des cibles de nourrissage des proies appétées et de leur interaction avec les composantes de l'écosystème, en particulier les plantes. La grande richesse du contenu pollinique observée dans les deux types de guano, bien que présentant 50 % de taxons communs, souligne des aires de nourrissage préférentielles. Elle montre aussi des fluctuations interannuelles, marqueurs probables de changements environnementaux, sinon climatiques. Cet article présente des premiers résultats obtenus sur le sondage HAK1 prélévé dans un amas de guano de salanganes de la grotte Hama sur l'île de Lifou, l'une des îles Loyautés. La comparaison entre les données de géochimie isotopique moléculaire (isotopes du carbone δ13C et de l'hydrogène δD du n-alcane C29) et les données pluviométriques met en évidence une bonne covariation interprétée comme marqueur du signal climatique ENSO contemporain des dépôts de guano analysés. Ce travail préliminaire confirme le fort potentiel des amas de guano cavernicoles pour étudier à haute résolution les changements paléo-environnementaux.
(Quaternaire. vol. 28, n° 1142-2904, pp. 401-412, 01/09/2026)
BTP, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IAC
The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period
Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard-Oeschger (D-O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on climate. Previous reconstructions of vegetation and fire changes during the D-O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here we present the ACER (Abrupt Climate Changes and Environmental Responses) global database which includes 93 pollen records from the last glacial period (73–15 ka) with a temporal resolution better than 1,000 years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (14C, 234U/230Th, OSL, 40Ar/39Ar dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on event stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts and pollen percentages of the characteristic biomes, and is archived in Microsoft AccessTM at doi:10.1594/PANGAEA.870867.
(Earth System Science Data. vol. 9, n° 1866-3508, pp. 679 - 695, 01/09/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PACEA, UB, CNRS, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, UOW, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, IPHES-CERCA, UMR ISEM, Cirad, IRD, EPHE, PSL, UM, CNRS, UNIROMA, IRD/CNPQ, USP, BTP, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, SBiK-F, LG / WGL, UNIMIB, NMK, MPIPZ, VU
Origin and distribution of the organic matter in the distal lobe of the Congo deep-sea fan – A Rock-Eval survey
The Congo River, the second largest river in the world, is a major source of organic matter for the deep Atlantic Ocean because of the connection of its estuary to the deep offshore area by a submarine canyon which feeds a vast deep-sea fan. The lobe zone of this deep-sea fan is the final receptacle of the sedimentary inputs presently channelled by the canyon and covers an area of ~2500 km². The quantity and the source of organic matter preserved in recent turbiditic sediments from the distal lobe of the Congo deep-sea fan were assessed using Rock-Eval pyrolysis analyses. Six sites, located at approximately 5000 m water-depth, were investigated. The mud-rich sediments of the distal lobe contain high amounts of organic matter (~3.5 to 4% Corg), the origin of which is a mixture of terrestrial higher-plant debris, soil organic matter and deeply oxidized phytoplanktonic material. Although the respective contribution of terrestrial and marine sources of organic matter cannot be precisely quantified using Rock-Eval analyses, the terrestrial fraction is dominant according to similar hydrogen and oxygen indices of both suspended and bedload sediments from the Congo River and that deposited in the lobe complex. The Rock-Eval signature supports the 70% to 80% of the terrestrial fraction previously estimated using C/N and δ13Corg data. In the background sediment, the organic matter distribution is homogeneous at different scales, from a single turbiditic event to the entire lobe, and changes in accumulation rates only have a limited effect on the quantity and quality of the preserved organic matter. Peculiar areas with chemosynthetic bivalves and/or bacterial mats, explored using ROV Victor 6000, show a Rock-Eval signature more or less similar to background sediment. This high organic carbon content associated to high sedimentation rates (> 2 to 20 mm.yr−1) in the Congo distal lobe complex implies a high burial rate for organic carbon. Consequently, the Congo deep-sea fan represents an enormous sink of terrestrial organic matter when compared to other turbiditic systems over the world.
(Deep Sea Research Part II: Topical Studies in Oceanography. vol. 142, n° 0967-0645, pp. 75-90, 01/09/2026)
EMBS, iSTeP, UPMC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GM, IFREMER, LDO, INSU - CNRS, UBO EPE, CNRS
First report of the invasive species Branchiomma bairdi McIntosh, 1885(Annelida: Sabellidae) along the Tunisian coast (Mediterranean Sea)
The invasive sabellid polychaete Branchiomma bairdi McIntosh, 1885 was collected in the Boughrara Lagoon (southern Tunisian coast) between 2012 and 2013. This species was originally described from Bermuda and has been widely reported in the Caribbean Sea. It has been considered as non-indigenous species on the Pacific coast of Panama and the California Gulf. Recently, B. bairdi was recorded along the Italian and Turkish coasts, Australia, Canary and Madeira Islands. It was suggested that the commercial shipping is the most likely vector for the introduction of the species to Mediterranean Sea. A description of the species along with a discussion of its systematic position and ecology are provided.
(BioInvasions Records. vol. 6, n° 2242-1300, pp. 139-145, 01/09/2026)
INSTM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LCE, CNRS, UMLP, UBFC