Cockle Cerastoderma edule population mortality: Role of the digenean parasite Himasthla quissentensis
Infection patterns of the digenean trematode Himasthla quissetensis in its second intermediate host, the edible cockle Cerastoderma edule, and the impact of this parasite on cockle populations were quantified. A 2 yr transplant experiment and a 4 yr survey were conducted in Arcachon Bay, a coastal lagoon on the Atlantic SW coast of France. Cockles free of H. quissetensis were transplanted at La Canelette, a station where cockles were usually highly infected. Infection began in May, when the water temperature reached 17degreesC and stopped in November (12degreesC). There was no new infection between November and April. Monthly surveys at 2 stations, Arguin and La Canelette, confirmed that cockle infection by H. quissetensis occurred during the warmer period of the year. Only cockles with a shell length > 8 mm became infected; therefore, cockle growth rate, which differed at the 2 stations, was also a key factor explaining infection phenology. In winter, the mean parasite abundance of H quissetensis in cockles decreased at both stations. The mortality rate of parasites in cockles was very low, with no seasonal pattern, and did not explain this winter decrease. Consequently, the decrease of H. quissetensis was interpreted as mortality of heavily infected cockles. At Arguin, where the cockle population was characterised by moderate abundance, high growth rate and short lifespan, cockle mortality amounted to 93% during the first year of benthic life, with no significant contribution of parasites; in the following year (Year 2), cockle mortality was 85%, with 28% due to H. quissetensis infection. At La Canelette, the cockle population, characterised by low abundance and low growth rate, suffered almost 100% mortality in the first year, with no contribution by parasites, which started to infect cockles in the second year only; the remaining cockles had a long lifespan (up to 5 yr), and > 46% of their mortality was linked to H. quissetensis infection. It is concluded that both host growth rate and water temperature are important factors in the initiation of parasite infection and that the intensity of infection and its effect on host mortality closely depend on host growth and environmental factors.
(Marine Ecology Progress Series. vol. 279, n° 0171-8630, pp. 141-150, 22/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Relationship between Antarctic sea ice and southwest African climate during the late Quaternary
Here we compare late Quaternary southwest African climate records from the west coast of southern Africa (published winter rainfall and trade wind intensity records from a core off the coast of Namibia) to records of Antarctic sea-ice extent. This comparison reveals coherent changes between Antarctic sea-ice extent and the southwest African winter rain region since 45 k.y. B.P., with enhanced winter rainfall and trade-wind vigor during periods of increased sea-ice presence. We propose an oceanic and atmospheric coupling between Antarctic sea ice and the winter rainfall zone of southwest Africa that may lead to increased desertification in the region if global warming persists.
(Geology. vol. 32, n° 0091-7613, pp. 909, 22/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CAU
MD 140 / PRIVILEGE cruise, RV Marion Dufresne
The French acronym MD 140/PRIVILEGE stands for integrated program valorised by IFREMER, LSCE, EPOC in geology. The survey covers 3 programs: the PRISMA, CADICOR, and PRIMAROSA sud 1. The objectives are: High resolution study of sediments and carbonate mounds (deep coral) off Morocco (CADICOR project), slides of submarine slopes related to seisms on the Algerian margin (PRISMA project), edification of deep sedimentary bodies linked to the circulation of Mediterranean water in the gulf of Cadiz and late Quaternary paleoclimatic variability, Ocean-Continent relationship (PRIMAROSA project). The related programs are Ifremer's margin program, IMAGES, GDR Marge, PNEDC, ECLIPSE Eurostrataform, Geomound, etc.
(22/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Relations entre qualité du substrat, flux de matières et activités humaines. Connaissance pour la gestion des ressources en eau de la Région Aquitaine
Les résultats de ce travail de recherche, confirment une fois de plus l'absence de déterminisme apparent entre qualité du substrat et occupation des sols. Ils montrent qu'il n'y a pas de variables prépondérantes ou explicatives de facteurs sociaux ou physiques qui soient responsables des variations affectant les milieux étudiés. Cependant, les analyses régressives des rapports entre homme et milieu montrent les liens étroits entre habitat et types de sol. L'action humaine a des effets sur la couverture végétale, sur les sols et sur l'hydraulique qui avec le climat et la topographie constituent les principaux facteurs d'érosion.
(22/02/2026)
ITEM, UPPA, UPPA, IPRA, UPPA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Recent organic-rich deep sedimentation off Southwest Africa: keys for understanding the deep offshore petroleum source-rock distribution.
The Atlantic South-eastern margin is influenced by the presence of broad upwelling cells associated with the Benguela Current System. Sedimentary records of cores taken from 35°S to 10°S between 1000 to 4000m depth show extraordinarily high organic carbon (OM) contents for this deep and oxygenated environment. Thus this margin is different from classically known models of preservation in deep setting by the bottom water anoxia or redepositional processes Temporal variability of organic carbon observed along this margin from the north of Walvis ridge to South Africa, shows an enrichment in total organic carbon (TOC) during the Last Glacial Maximum (20kyrs) with respect to Holocene Climatic Optimum(8kyrs). It is the same for biogenic silica, mainly related to diatoms input, which follows the same climatic logic. Carbonate contents are negatively correlated with TOC and biogenic silica. The Lüderitz upwelling cell is presently the most productive area of the Benguela Current System, during at least 280 kyrs, and abundant OM accumulates on the adjacent slope sediments even at great water depth. Results indicate that OM is more oxidized at 3606 m water depth than on the upper slope sediments (1029 m) although petroleum quality of OM throughout the deep-water core remains surprisingly high for hemipelagic deep-sea sediments (HI = 200 to 400 mg HC/g TOC). The petroleum quality of OM accumulated on the upper slope is consistently high: HI average 450 mg HC/g TOC. Organic sedimentation in front of Lüderitz is modellised with the software DIONISOS (IFP), in the aim of developping a 3D stratigraphic model and predicting petroleum quality and quantity of organic matter along the margin. The first step in modelling the deep organic matter sedimentation is to decipher between the main controlling factors the key parameters to be introduce in the model DIONISOS. This imply to define simple laws for productivity, degradation, advection of sediment, etc. Rock Eval parameters shows that organic sedimentation along the margin can be considered as an important source-rock sedimentation. Source-Rock Potential Index (SPI) calculations are in agreement with a maximum of a potential hydrocarbon formation in front of Lüderitz, from shallow depth (500m), to deeper depth (2000m). We believe that the probability that such organic-rich facies occurred in the past in equivalent oceanographic settings at the edge of large oceanic basins should be carefully considered in deep offshore exploration.
(22/02/2026)
MNHN, UPMC, CNRS, ISTO, INSU - CNRS, UO, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFPEN, LMMNHN, MNHN, CNRS
Roller modelling in the context of undertow prediction
In this paper we investigate the energy-based roller equations previously published by Stive and De Vriend (1994) and Dally and Brown (1995). Although these models differ by a factor of 2 in one of their terms, the same parameter values are commonly used to solve them. Our aim is to elucidate these discrepancies and to explore the physical adequacy of the roller models by using an inverse modelling technique based on undertow measurements. Comparison with Cox (1995) experimental data on regular waves propagating on a planar beach shows that a realistic contribution of potential energy in the roller equation should be included.
(pp. 318-330, 22/02/2026)
LEGI, UJF, Grenoble INP, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Tracing the source of Upper Palaeolithic shell beads by strontium isotope dating
While the identification of the source of shells used as personal ornaments is crucial for determining home range and exchange networks of prehistoric hunter-gatherers, it is often difficult to identify the coastal versus fossil origin of the shells as most genera used as beads were available both at beaches and fossil outcrops. Here we present the first application of 87Sr/86Sr isotope dating to identify the origin of Upper Palaeolithic shell beads. We analysed four out of a collection of one thousand Dentalium shells associated to the La Madeleine child burial dated to 10; 190G100 BP and one Dentalium from the occupation layers of this site. 87Sr/86Sr ratios indicate that shells were collected by Late Upper Palaeolithic beadworkers on far away beaches rather than at nearer Miocene outcrops. This may be due to the narrowness of Miocene Dentalium shells, incompatible with the size of bone needles used to sew these shell beads on clothes.
(Journal of Archaeological Science. vol. 31, n° 0305-4403, pp. 1481-1488, 22/02/2026)
ArScAn, UP1, UP8, UPN, MCC, CNRS, PACEA, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A stationary Mediterranean forest in southweastern Iberia during OIS 3 ? A reply to Carrion.
(Quaternary Science Reviews. vol. 23, n° 0277-3791, pp. 1217-1224., 22/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PACEA, UB, CNRS
Recent sedimentation of organic matter along the SE Atlantic Margin : A key for understanding deep offshore petroleum source rocks.
Classical views for the deposition of organic-rich sediments in deep-sea environments invoke two principal types of oceanographic and sedimentologic settings. The first is confined basins in which stratified oxygen depleted waters lead to anoxic preservation of organic matter in the water column and in underlying sediments (Demaison and Moore, 1980). The second is an open ocean setting where the episodic mass transfers due to slope sediment instability lead to the rapid burial of outer-shelf and upper slope-derived organic matter and its consequent preservation due to limited oxic or anoxic degradation (Stow, 1987). Other studies have shown, however, that organic matter in modern deep-sea sediments may occur in high amounts where oxygen is not significantly depleted (Pedersen and Calvert, 1990). Recent studies have demonstrated that highly biological productive areas, such as the upwelling zones associated to the Benguela Current in S-E Atlantic, may deliver sufficient quantity of organic material to (1) outbalance the degradative capacity of the water column and (2) sustain the formation of organic-rich sediments even in deep and oxygenated conditions (Bertrand et al., 2003). It appears that the S-E Atlantic margins provide a good example for revisiting the sedimentology of organic matter in deep water environments in the frame of the GDR Marges Continentales. This may have important implications for a better understanding of the distribution of ancient source rocks in deep offshore petroleum systems (Huc et al., 2001; Bertrand et al., 2003).
(pp. 6p., 22/02/2026)
MNHN, UPMC, CNRS, ISTO, INSU - CNRS, UO, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFPEN, LMMNHN, MNHN, CNRS, G2R, UHP, INPL, CREGU, CNRS
Environmental impact of early Basque mining and smelting recorded in a high ash minerogenic peat deposit
More than four metres of core, covering almost 5000 years of deposition, were collected in a high ash minerogenic peat deposit located in the High Aldudes valley (Basque country), an area well known for its mineral abundance, exploited from Roman Times at least.Although minerogenic peatlands are not generally considered as the best archives to reconstruct past atmospheric metal deposition history, lead isotopic geochemistry demonstrates the integrity of the Pb record at least within the three upper meters; that is to say over the last four millennia.Zn, Cd and Cumay have been widely redistributed either by biological cycling, advective groundwater movements, or diffusional processes.Anthr opogenic lead input phases are clearly pinpointed by positive shifts in PbySc ratios with concomitant sharp drops in 206Pby207Pb ratios.They are often accompanied by significant declines in tree taxa, interpreted as increasing demand for wood to supply energy for local mining andyor metallurgical operations.Periods of mining andyor smelting activity are identified during Antiquity and Modern Times, and are also confirmed by textual and field evidence.Inputs from the Rio Tinto (Southern Spain), often invoked as a major lead contributor to the European atmosphere during Roman Times, were not detected here.This remote source was probably masked by local inputs. Other mining andyor smelting phases, only suspected by archaeologists, are here identified as early as the Bronze Age.Although the durations of these phases are possibly overestimated because of detrital inputs consequent to the release of lead from polluted soils over a long period of time after major pollutant inputs, the periods at which pollution peaks occur are in good agreement with archaeological knowledge and palaeo-botanical data.Thecombination of geochemical and palaeo-botanical techniques with field archaeology, therefore provides a powerful tool in studying the interaction of early human societies with their environment, as regards early mining and smelting.
(Science of the Total Environment, n° 0048-9697, pp. pp. 197-214, 22/02/2026)
GéoSol, INRA, UB, LCE, CNRS, UFC, UBFC, Inrap, LA, EHESS, UT2J, Comue de Toulouse, UT3, Comue de Toulouse, CNRS, UB, CNRS, UNIGE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS