Diatoms preserved in surface sediments of the northeastern Kerguelen Plateau
An ''island mass effect'' was observed from the sedimentary distribution of diatoms on the northeastern Kerguelen Plateau. Five new samples placed in context to species distributions previously reported from the Permanently Open Ocean Zone (POOZ) revealed a plateau community dominated by three species/taxa: Fragilariopsis kerguelensis, Thalassionema nitzschioides f. nitzschioides and Chaetoceros Hyalochaete resting spores. Intermediate abundances of Thalassiosira antarctica were unique to the plateau sediment signature as were increased abundances of Eucampia antarctica v. antarctica. The off-plateau sediment sample contained typical POOZ sediment distributions dominated by F. kerguelensis, Thalassiosira lentiginosa and Thalassiothrix antarctica. The role of deposition from the surface waters to the sediments was investigated by comparison to the diatom thanatocoenose observed in surface waters. These results suggest that the use of sediment abundances of C. Hyalochaete resting spores and F. kerguelensis to determine past productivity events (such as wind-sourced iron enrichment of the Southern Ocean at the Last Glacial Maximum) is not straightforward. The elevated abundance of T. nitzschioides f. nitzschioides on the plateau did not indicate an iron-deplete regime but the converse. For the evaluation of paleo-productivity hypotheses for the open Southern Ocean, we suggest caution in the use of Subantarctic and Kerguelen Plateau sediment signatures, and emphasize that there is a need to also study Antarctic coastal and especially sea-ice melt-water stimulated blooms. r
(Deep Sea Research Part II: Topical Studies in Oceanography. vol. 55, n° 0967-0645, pp. 677-692, 10/04/2026)
LOB, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, LMGEM, CNRS
Seasonal record of foraminiferal export fluxes in the Bay of Biscay
(10/04/2026)
LPGN, UN, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
SPM fluxes estimates from discrete monitoring : comparison of calculation methods and uncertainties
The SPM (suspended particulate matter) fluxes temporal variabilities are even more complex than water flows and are therefore very difficult to estimate. In France, SPM are surveyed within the national water quality survey system (RNB) and are monitored with a bimonthly or monthly frequency, as other water quality indicators. The flux calculation methods and their related uncertainties on the basis of an experimental data set of continuous – i.e. daily monitoring for contrasted river basins ranging from 100 to 100 000 km2 (in France and in USA, 60 stations totalling 600 station-year of daily SPM and flows). The uncertainties, biases, and errors, result from the analysis of the distribution of errors made on simulated surveys at various frequencies (3, 5, ... 30 days) in comparison to the same value. The duration curves of SPM fluxes and the key indicator M2 %, i.e. the percentage of SPM carried in 2 % of time on a multiannual period (4 to 20 y), are then determined. The M2 % indicator is used to build-up a nomograph linking biases (median or errors) and imprecision (difference between upper and lower deciles of errors) to monitoring frequencies (3, 4, ... 30 days). This nomograph can be used to : i) optimize surveys frequencies, given a flux error target, or to ii) associate error bars. The nomograph is so far established for the mean discharge-weighted concentration method, one of the most common method with the rating curve method.
(La Houille Blanche - Revue internationale de l'eau. vol. 4, n° 0018-6368, pp. 64 à 71, 10/04/2026)
SISYPHE, UPMC, EPHE, PSL, PSL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, LTHE, OSUG, UJF, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, IRD, INSU - CNRS, INPG, CNRS, EDF [E.D.F.], AEE
Sea ice seasonality during the Holocene, Adélie Land, East Antarctica
Thin sections of laminated cores from different Antarctic coastal areas have demonstrated the potential of diatom species to document climate change at the seasonal scale. Here we present the relative abundances of four diatom species and species groups (Fragilariopsis curta group as a proxy for yearly sea ice cover, F. kerguelensis as a proxy for summer sea-surface temperature, Chaetoceros Hyalochaete resting spores as a proxy for spring sea ice melting and the Thalassiosira antarctica group as a proxy for autumn sea ice formation) in core MD03-2601 retrieved off Adélie Land on the Antarctic continental shelf. These abundances were compared to surface temperatures and sea ice cover modelled over the last 9000 years. Both the marine records and the simulated climate demonstrated a cooler Early Holocene (9000-7700 years BP), a warmer Mid-Holocene (7700-4000 years BP) and a colder Late Holocene (4000-1000 years BP). Yearly sea ice cover followed an inverse pattern to temperatures with less sea ice during the Mid-Holocene Hypsithermal than during the Late Holocene Neoglacial. However, diatom census counts and model output indicate that sea ice spring melting happened earlier in the season, as expected, but that autumn sea ice formation also occurred earlier in the season during the Hypsithermal than during the colder Neoglacial, thereby following seasonal changes in local insolation.
(Marine Micropaleontology. vol. 66, n° 0377-8398, pp. 222-232, 10/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Identification of a minimal adequate model to describe the biomass dynamics of river epilithon
(River Research and Applications. vol. 24, n° 1535-1459, pp. 36-53, 10/04/2026)
LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The Fetch Campaign, study of the turbulent fluxes, surface waves and remotely sensed parameters in fetch limited situations
description of the Fetch Campaign conducted in the Golfe du Lion in Mediterranéean sea
(10/04/2026)
CETP, UVSQ, INSU - CNRS, CNRS, SA, UVSQ, UPMC, INSU - CNRS, CNRS, IRPHE, AMU, ECM, CNRS, LEPI, UTLN, APL/RSMAS, RSMAS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LAERO, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNRS, FIMR, DIROP/MAR, DIROP, IFREMER
Cadmium uptake by the European eel: Trophic transfer in field and experimental investigations
Due to its status of threatened species and being heavily contaminated by metals, the European eel (Anguilla anguilla) was selected to investigate cadmium contamination levels of fish settled along a historically cadmium-contaminated hydrosystem, the GaronneGironde continuum (France), according to its various location sites and fish length. Results have shown an important site effect on cadmium concentrations in liver but not in gills, highlighting the possible predominance of the trophic exposure route. Subsequently, uncontaminated eels were experimentally exposed to cadmium by water uptake and/or trophic route(s). Eels were fed with different preys: white shrimps collected in an unpolluted area in the Gironde estuary, and cadmium-enriched shrimps. Data obtained tend to show that the use of cadmium-enriched food during experimental investigations triggers an underestimation of the metal trophic transfer rate. These two complementary approaches provide some elements to suggest that the trophic route plays an important role in cadmium contamination of wild eels.
(Ecotoxicology and Environmental Safety. vol. 70, n° 0147-6513, pp. 10-19, 10/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EPBX, CEMAGREF
Impacts of gold nanoparticle exposure on two freshwater species: A phytoplanktonic alga (Scenedesmus subspicatus) and a benthic bivalve (Corbicula fluminea)
For years, nanotechnologies have developed the use of common materials, such as iron or silica, at an extremely small scale because of their new properties (reactivity, conductivity, optical sensitivity). More precisely, gold nanoparticles are used in numerous technologies such as electronics, new paints or research on cancer. But, despite their promising future and expansive utilization, only a few studies deal with their behaviors or impacts on the environment. Thus, we decided to explore the impacts of amine-coated 10nm gold nanoparticle (AuNp) contaminations on two freshwater aquatic models. The green algaScenedesmus subspicatus was submitted to 24 h-direct exposures at four AuNp concentrations (1.6×102, 1.6×103, 1.6×104 and 1.6×105 AuNp/cell) along with a control condition. The process used for the freshwater bivalvesCorbicula fluminea was a trophic exposure during 7 days to three AuNp concentrations (1.6×103, 1.6×104 and 1.6×105 AuNp/cell). These conditions were tested in triplicate with controls. For these experiments, OD measurements (γ= 520nm) were performed to verify AuNp concentrations in the water (stability). Cell numerations of algae were used to determine the growth/mortality effects on this species. Cellular impacts and AuNp distributions in the two species were revealed by transmission electron microscopy (TEM). The bioaccumulation rates were assessed by gold dosagesvia MS-ICP procedures. Molecular impacts were analyzed by quantifications of metallothionein concentrations (metal detoxification protein) and genetic expressions via real-time RT-PCR. Our study focused on the expression of six genes encoding proteins involved in: metal detoxification (metallothionein), the response to oxidative stress (catalase and superoxide-dismutase), the mitochondrial respiratory chain (subunit 1 of the cytochrome-C-oxidase), the concentration of mitochondria (RNA12s) and the response to xenobiotics (glutathione S transferase); using the β-actin as reference of the basal rates of gene expressions.
(Gold Bulletin : The journal of gold science, technology and applications. vol. 41, n° 2364-821X, pp. 116-126, 10/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Nitrous oxide emissions from tropical hydroelectric reservoirs
We report original data on nitrous oxide (N2O) fluxes from two tropical reservoirs, their rivers below the dam, and from natural aquatic ecosystems and rainforest soils in French Guiana and Panama. We also review published N2O fluxes from other tropical reservoirs and natural environments. We show that: (1) N2O emissions from tropical reservoirs occur mainly at the reservoir surface, fluxes downstream of dams being minor; (2) Because pre-flooding natural N2O fluxes are significant, the net N2O emissions from reservoirs are less than ∼50-70% of gross N2O emissions; (3) the contribution of N2O to the global warming potential of emissions from reservoirs could be significant for gross emissions, but less than 10% for net emissions, disregarding N2O degassing emissions.
(Geophysical Research Letters. vol. 35, n° 0094-8276, pp. L06404, 10/04/2026)
LAERO, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LACy, INSU - CNRS, UR, 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, 10/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LRHA, HGS, IFREMER