Contribution du cadmium au déclin des populations d'anguille européenne (Anguilla anguilla) : impact sur la réussite de la migration de reproduction
Les populations d'anguille européenne (Anguilla anguilla L.) déclinent sévèrement depuis quelques décennies, menaçant cette espèce d'extinction. Dans ce contexte, nous avons étudié l'effet potentiel du cadmium (Cd), un métal non essentiel largement répandu dans l'environnement, sur les capacités de reproduction de l'anguille européenne.
(pp. 1, 27/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MNHN, UR EPBX, CEMAGREF
Silver behaviour along the salinity gradient of the Gironde estuary: reactivity and bioaccumulation in eel (anguilla anguilla)
The objective of the present work is to document for the first time Ag concentration levels and behaviour in the salinity gradient of the highly turbid, macrotidal Gironde Estuary. Furthermore, a potential impact of estuarine Ag dissolution on bioaccumulation in European eels is discussed.
(pp. 2, 27/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EPBX, CEMAGREF
How cadmium could compromise the completion of the european eel's reproductive migration
The European eel (Anguilla anguilla L.) is severely threatened with extinction. Surprisingly, even though their unusual life cyclemakesthem particularly vulnerable to pollution, the possible contribution of contamination remains especially poorly known. Here we have investigated the possible effect of cadmium (Cd), a widespread nonessential metal, on eel reproductive capacities. Both control and Cd precontaminated female silver eels were experimentally matured and forced to swim in metal-free conditions to mimic their reproductive migration. Cd pre-exposure was found to strongly stimulate the pituitary-gonad-liver axis of maturing female silver eels leading to early and enhanced vitellogenesis. This was followed by a strong phenomenon of oocyte atresia and eel mortality. These phenomena occurred before oocytes could reach full maturation and were associated with a large entry of both vitellogenin and Cd into the ovaries. Indeed, a redistribution of previously stored cadmium, even from the low Cd levels of control eels, was observed during sexual maturation. Atresia and mortality phenomena were also associated with an overexpression of the pituitary gene encoding the growth hormone, a marker of physiological stress and energy reserves exhaustion. Significantly, these devastating effects of Cd were observed in organisms that presented liver and kidney Cd concentrations still below those observed in eels from Cd contaminated hydrosystems. Our research shows how common levels of cadmium contamination could disrupt endocrine pathways implicated in gonad maturation and subsequently impair reproductive capacity of eel future genitors.
(Environmental Science and Technology. vol. 42, n° 0013-936X, pp. 4607-4612, 27/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CNRS, BOME, MNHN, UPMC, CNRS, UR EPBX, CEMAGREF
Application de la théorie SLOSS (Single Large or Several Small) aux communautés périphytiques de deux cours d'eau : à superficie égale, est-il préférable d'échantillonner une grande réserve ou plusieurs petites?
La théorie de la biogéographie insulaire repose sur le fait que la richesse spécifique des peuplements fragmentés dépend de l'équilibre entre taux d'immigration et taux d'extinction, la taille des « réserves naturelles » de l'habitat étant susceptible de conditionner l'efficacité de la conservation de la biodiversité (Diamond, 1975). La distribution spatiale des communautés pose dans la pratique le problème de bien déterminer la taille des réserves à étudier afin d'éviter le sous-échantillonnage. Dans cette étude des communautés périphytiques (diatomées et bactéries) de la Vézère et de la Garonne, nous avons cherché à identifier les apports du choix, à superficie identique échantillonnée, d'un prélèvement sur substrat de grande taille (Single Large) vs. plusieurs petits (Several Small). Des analyses quantitatives globales révèlent que les tendances sont variables selon le cours d'eau et selon les paramètres étudiés (matière sèche, chlorophylle, densité de diatomées). En règle générale, la quantité de biomasse par unité de surface est plus importante pour les grands substrats échantillonnés, soutenant la théorie selon laquelle une grande réserve est plus efficace que deux plus petites de superficie égale. L'étude qualitative souligne également l'influence de la taille de la réserve échantillonnée, en termes de diversité mais également en termes de structure spécifique, la composition des prélèvements réalisés sur substrats de plus grande taille indiquant une complexification plus rapide de la communauté.
(pp. 1, 27/05/2026)
UR REBX, CEMAGREF, LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Live (stained) benthic foraminifera from the Rhone prodelta: environmental controls and temporal variability
(27/05/2026)
BIAF, UA, LPGN, UN, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, OCEANIS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CEFREM, UPVD, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Brown muscle disease (BMD), an emergent pathology affecting Manila clam Ruditapes philippinarum in Arcachon Bay (SW France)
We describe an emerging pathology, brown muscle disease (BMD), which specifically affects the Manila clam Ruditapes philippinarum in Arcachon Bay (France). BMD induces a transformation of the posterior adductor muscle, which becomes infused by conchiolin and calcified, reducing the ability of clams to bury. The disease affects both types of muscular tissue, with striated muscle becoming affected to a higher degree than smooth muscle. Two indices were created to quantify the symptoms: the Muscle Print Index, used for empty and live shells, and the Final Disease Index, utilized for live clams only. Histological sections were made and observed under light microscopy to examine the muscular damage and to investigate a causal agent. Sections revealed an important inflammatory response with a large invasion of hemocytes into tissues and a heavy necrosis of muscular fibers. Additionally, molecular biology analyses were carried out to search for bacteria and protozoan agents using generic primers. In both histological and molecular assays, bacteria and protozoans were discounted. We monitored 4 sites scattered around the bay over 2 yr. The mean prevalence was <12% without seasonal variation in 3 sites against 30% and a winter peak in 1 site. The latter site was accurately surveyed and revealed that clams at the sediment surface (abnormal position) were affected 3 times more frequently than buried clams (normal position)
(Diseases of Aquatic Organisms. vol. 80, n° 0177-5103, pp. 219-228, 27/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LRHA, HGS, IFREMER
Particle fluxes and recent sediment accumulation on the Aquitanian margin of Bay of Biscay
(27/05/2026)
LPGN, UN, CNRS, LOV, OOVM, UPMC, INSU - CNRS, CNRS, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Seasonal export of plankton foraminifera in the Bay of Biscay
(27/05/2026)
LPGN, UN, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The "storm of the century" (December 1999) and the accidental escape of Siberian sturgeons (Acipenser baerii) into the Gironde estuary (Southwest France): an original approach for metal contamination
Goal, Scope and Background. The Gironde estuary is considered as a reference ecosystem with a large fish assemblage (75 species) and the presence of eleven diadromous species. However, geochemical studies and biomonitoring using oysters have shown high metal pollution levels. During the December 1999 hurricane, more than 5,000 young Siberian sturgeons (Acipenser baerii) accidentally escaped from a fish farm into the estuary, where this species had not been present until then. Methods. In 2002/2003, thirteen sturgeons were collected from the estuary and twelve were obtained from the fish farm, from the same initial batch. Analysis of five metals (cadmium, zinc, copper, lead, mercury) measured in the gills, muscle, liver and kidneys, revealed significantly higher levels of cadmium, lead and mercury in the sturgeon collected from the estuary compared with those from the fish farm. Results and Discussion. Metal analysis of the stomach contents of fish collected from the estuary and artificial food used in the fish farm indicated that dietary exposure might account for the differences observed. Nevertheless, metal concentrations in sturgeons that had spent about three years in the Gironde estuary may be considered low when compared with other species (mullets, eels) or with data in the literature regarding concentrations able to induce structural and functional perturbations in fish. As the introduced Siberian sturgeons live in the same place and feed on the same prey as the juveniles of the endangered A. sturio, our results indicate in the short term that this strictly protected species does not appear to be much affected by the polymetallic pollution in the Gironde estuary. Marked differences in the concentrations of three metals (Cd, Pb, Hg) were established in four organs (gills, liver, skeletal muscle, kidneys) of Siberian sturgeons between specimens that had accidentally escaped into the Gironde estuary (France) during the December 1999 hurricane and were collected in March/June 2003 and specimens from the same initial batch at the fish farm. Recommendations and Perspectives. Based on these results, a programme will be set up, with sampling campaigns carried out in the estuary every two years, with systematic monitoring of age in order to check the origin of individuals, in conjunction with sampling of sturgeon from the fish farm. This programme will complement other studies on several biological species representative of the main trophic levels in the estuary, especially the plankton component, benthic macroinvertebrates and oysters.
(Environmental Science and Pollution Research. vol. 15, n° 0944-1344, pp. 89-94, 27/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EPBX, CEMAGREF, UB
Seasonal effects of cadmium accumulation in periphytic diatom communities of freshwater biofilms
The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mort River (SW, France) were studied in July 2004 and March 2005. Biofilms were sampled from artificial substrates immersed along a metallic pollution gradient during 20 days. Dynamics of diatom communities and cadmium accumulation were followed by collecting samples after 4, 7, 14 and 20 days of biofilm colonization. Cd accumulation in biofilms during experiment was significantly higher in Cd polluted station (Joanis) than in reference station (Firmi) for both seasons. Periphytic diatom composition varied between sites and seasons. At Firmi station, seasonal dynamics of diatom communities were stable with the dominance of Cyclotella meneghiniana and Melosira varians in July and Surirellabrebissonnii and Navicula gregaria in March. At Joanis station, diatom communities mainly responded to high levels of metal by a high proportion of small, adnate species. Positive correlations between Eolimna minima, Nitzschia palea, Encyonema minutum, Surirella angusta, and Gomphonema parvulum and cadmium accumulation were observed, indicating that these species are tolerant to high levels of cadmium. On the other hand, negative correlations of C. meneghiniana, N. gregaria, Navicula lanceolata, M. varians and Nitzschia dissipata with cadmium qualify them as sensitive diatom species. Periphytic diatom composition through the presence of specific species highlight metal tolerant indicator diatom groups which will be meaningful for biomonitoring pollution in natural aquatic systems.
(Aquatic Toxicology. vol. 90, n° 0166-445X, pp. 19-28, 27/05/2026)
IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR REBX, CEMAGREF