Interspecific variability of fatty acid profiles of the two freshwater diatoms, Gomphonema gracile and Nitzschia palea, in comparison with classical descriptors and in response to herbicides contaminations
Many studies showed the impact of pesticides on diatom's metabolism. Diuron decreases the photosynthetic activity and synthesis of polyunsaturated fatty acid whereas s-metolachlor decreases the synthesis of long chain fatty acids. Fatty acids (FA) are essential elements for the structure of biological membranes and for the storage of metabolic energy. For example polyunsaturated fatty acids (PUFA) play a key role in membrane fluidity. Various studies demonstrated impacts of chemical contamination on fatty acid profiles. Furthermore, variability of fatty acid profiles of marine microalga in response to herbicides has been proved. However, to our knowledge scarce studies showed the interspecific variability of fatty acid profiles of freshwater diatoms especially in response to a pesticide contamination. The aims of this study were to investigate the interspecific variability of two freshwater diatoms on photosynthesis, growth rate, concentration in chlorophyll a and carotene and induction or repression of interest genes; Study this variability on fatty acid profiles; with and without pesticides. To address this issue, two model freshwater diatoms, Gomphonema gracile (GGRA) and Nitzschia palea (NPAL), were exposed separately during seven days to diuron and s-metolachlor at high concentration (C=10 µg/L) and at 20.5°C. For control condition, NPAL had a higher chlorophyll a and carotenoid concentration than GGRA. An interspecific variability of fatty acid profiles was observed with a lower percentage of saturated fatty acid (SFA) and highly unsaturated fatty acid (HUFA) for NPAL than GGRA. However, NPAL had a higher percentage of 22:6n3 than GGRA. Diuron decreased the percentage of chlorophyll a and carotenoid concentration of NPAL while no significant effect was observed for GGRA. Diuron increased percentage of SFA for NPAL whereas a decrease was noted for GGRA; the percentage of 14:0 and 16:0 increased for NPAL while it decreased for GGRA. NPAL had a different fatty acid profile compared to GGRA and seemed to have diverging mechanisms of protection in response to a contamination. This study proved the importance to taking into account interspecific variability of fatty acid profiles of diatoms for further use them as biomarkers of toxic contamination in fresh waters.
(pp. 27, 27/04/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CNRS
Molecular analysis and new records of the invasive polychaete Boccardia proboscidea (Annelida: Spionidae)
The spionid polychaete Boccardia proboscidea Hartman, 1940 is a tube-dweller and shell/stone-borer widely occurring in temperate waters across the world and considered invasive in many areas. It was originally described from California, USA, and later reported from Pacific Canada, the Asian Pacific, Australia, New Zealand, Argentina, South Africa, and northern Europe. The Bayesian inference analysis of sequence data of three gene fragments (836 bp in total) of the mitochondrial 16S rDNA, nuclear 28S rDNA, and Histone 3 has shown that individuals from the Pacific coasts of Canada and the USA, Argentina, Australia, South Africa, the United Kingdom, and Mediterranean France were genetically very similar (maximal average p-distance value, 0.49%, was between 16S rDNA sequences). We consider these individuals to be conspecific and report the earliest records of B. proboscidea from the UK and a possible first Mediterranean record in the Gulf of Lion. The high 16S haplotype diversity of B. proboscidea detected in the north-eastern Pacific suggests a native distribution for the species in the northern Pacific and subsequent introductions through human activities to other parts of the world. The histories of these introductions are reviewed and the hypotheses about times and places of introductions are updated.
(Mediterranean Marine Science. vol. 20, n° 1108-393X, pp. 393-408, 27/04/2026)
LECOB, SU, CNRS, OOB, SU, CNRS, SBR, SU, CNRS, LEP, EEP, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Guess who? On the importance of using appropriate name: case study of Marphysa sanguinea (Montagu, 1813)
The common bait worm Marphysa sanguinea (Montagu, 1813), originally described from the south coast of England, is the type species of the genus. This species has been widely reported from all around the world and has been considered as cosmopolitan until recently. This is partly because the original description was very brief and poorly illustrated, and also because all species superficially look similar. In order to clarify the situation, M. sanguinea was redescribed and a neotype was designated by Hutchings and Karageorgpoulos in 2003. Recently, specimens from Cornwall, close to the type locality, were sampled, examined morphologically, and used to obtain COI gene sequences for this species. Molecular results permitted us to confirm the identity and presence of M. sanguinea along the French coasts and to highlight the presence of inaccurate sequences of this species on GenBank. Use of this “false” cosmopolitan species at a worldwide scale by many biologists is also discussed in this paper.
(Zookeys. vol. 859, n° 1313-2989, pp. 1-15, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMS POREA, INSU - CNRS, CNRS, INRAE, IRD, UBO EPE, CNRS, UFRJ
Technical note: On the importance of a three-dimensional approach for modelling the transport of neustic microplastics
Understanding and estimating the distribution and transport of microplastics in marine environments has been recognized as a major global research issue. Most of the existing research on transport modelling has focused on low-density particles floating in surface waters, using a 2-D Lagrangian approach and ignoring the vertical displacement of particles. In this work, we evaluate to what extent the vertical movement of particles within surface waters by mixing processes may affect the horizontal transport and fate of microplastics. The aim is to determine whether a 2-D approach is sufficient for the accurate modelling of neustic-microplastics transport or whether a 3-D approach is necessary. For this purpose, we compare visually and statistically the microplastics transport patterns of three simulations in a coastal system: one using a 2-D approach; and two using a 3-D approach with weak and strong vertical turbulence, respectively. The 2-D simulation roughly reproduced the transport and accumulation patterns, but accurate results required a 3-D approach. This was particularly important for strong vertical turbulence and regions characterized by strong vertical current shear. Moreover, a 2-D approach can lead to errors in the results even with negligible turbulence due to simplifications in the velocity field. A 3-D modelling approach is therefore key to an accurate estimation and prediction of microplastics distribution in coastal systems and consequently for planning mitigation and cleaning programmes.
(Ocean Science. vol. 15, n° 1812-0784, pp. 717-724, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNSW
Millennial-scale Holocene hydrological changes in the northeast Atlantic: New insights from ‘La Grande Vasière’ mid-shelf mud belt
A mid- to late-Holocene paleohydrological reconstruction from the northeast Atlantic is proposed through the study of a high-resolution sedimentary record from the northern continental shelf of the Bay of Biscay (BoB). Three foraminiferal species dominate the assemblages with Rosalina globularis showing an overall decrease in absolute and relative abundances from ~7 to 0.4 cal. ka BP, whereas the opposite trend is observed for Cibicides refulgens and Lobatula. These long-term patterns are interpreted as a response to the overall cooling trend and/or the progressive deepening of the water column because of the relative sea-level (RSL) rise. Foraminiferal δ18O and grain-size analyses show a significant shift around 3.5–2.5 cal. ka BP toward a heavier isotopic signature and finer sediments. We mainly link this change to enhanced contribution of continental freshwaters and fine sediments after the near-stabilization of the RSL rise. By reducing coastal accommodation spaces, this led to a better channelization of river outflows and probably to the formation of the modern winter thermohaline front. Superimposed on these long-term patterns, our data highlight strong millennial-scale variability (1250-year peak). Such cyclicity is consistent with several records tracing changes in rainfall and storminess regimes in northern Europe, and the dynamics of the subpolar gyre (SPG). We suggest a millennial time-scale control of a NAO-like (North Atlantic Oscillation) climatic process modulating continental humidity (and the associated river discharges) and SPG dynamics through wind stress. Spectral analyses reveal an additional 500-year frequency peak implying a possible solar forcing.
(The Holocene. vol. 29, n° 0959-6836, pp. 467-480, 27/04/2026)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, LGO, UBS, IFREMER, UBO EPE, CNRS, GM, IFREMER, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Fouiller sur l'estran : des contraintes et des opportunités
Sur estran, les vestiges apparaissent très bien conservés et parfois même immédiatement apparents lors de périodes d’érosion. Mais les contraintes s’accumulent à tous les niveaux : temps d’intervention limité, présence de l’eau, alternance des marées, rapidité de l’érosion dans certains secteurs, conditions d’accès ou de fouille, difficulté de mise en place d’infrastructures lourdes. Pour ces raisons, les interventions sur cet espace sont longtemps restées limitées à de simples observations accompagnées de prélèvements. La montée en puissance des problématiques littorales et l’accélération des processus d’érosion a alors motivé la mise au point de véritables projets de prospection et de fouille. Réalisés ni dans des conditions terrestres classiques ni dans des conditions subaquatiques, ces opérations ont souvent nécessité une méthodologie originale et l’appel à de nouveaux outils ou des modalités de prélèvements particulières. Quelques exemples choisis dans des contextes variés illustrent la réactivité et les adaptations nécessaires à des sites généralement bien conservés, souvent dotés de vestiges organiques, voire de restes de poissons ou de crustacés.
(Les Nouvelles de l'archéologie, n° 0242-7702, pp. 48-52, 27/04/2026)
CReAAH, UM, UR, UR2, CNRS, UFR HHAA, UN, MC, DRAC Normandie, MCC, MC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UP1, CNRS, Inrap, LASCARBX, UB, UBM, LETG - Brest, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, UBM, CNRS
Spatial variability and sources of platinum in a contaminated harbor – tracing coastal urban inputs
Biogeochemical cycles that include processes to control platinum (Pt) distribution remain widely unknown in aquatic environments, especially in coastal systems. Dissolved Pt concentrations in coastal seawater (PtD) and in suspended particulate matter (SPM, PtP) were measured, together with master variables comprising dissolved oxygen, dissolved and particulate organic carbon, chlorophyll-a, turbidity, and ammonium levels, along two longitudinal profiles in the industrial Genoa Harbor (north-west Italy). Concentrations and spatial distribution of PtD and PtP levels reflect distinct concentration gradients that were attributed to different Pt sources such as hospital, domestic and industrial wastewater, atmospheric deposition, and/or road runoff. Concentrations reaching up to 0.18 ng L−1 PtD and 14 ng g−1 PtP reflect the impact of Pt urban inputs to coastal sites. These first data highlight considerable anthropogenic contamination in a confined harbor compared with the proposed reference value for the western Mediterranean surface seawater measured at external sites. Identified correlations between Pt levels and human pollution signals suggest the potential use of Pt as a new tracer of anthropogenic inputs that can be applied to other urbanised coastal systems. Biogeochemical processes that induce changes in the partitioning and fate of Pt in coastal seawater reflect a spatial variability and highlight the need for comprehensive environmental monitoring at an appropriate spatial scale.
(Environmental Chemistry. vol. 17, n° 1448-2517, pp. 105-117, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNIGE, UniGe
Coral carbon isotope sensitivity to growth rate and water depth with paleo-sea level implications.
Although reef coral skeletal carbon isotopes (δC) are routinely measured, interpretation remains controversial. Here we show results of a consistent inverse relationship between coral δC and skeletal extension rate over the last several centuries in Porites corals at Fiji, Tonga, Rarotonga and American Samoa in the southwest Pacific. Beginning in the 1950s, this relationship breaks down as the atmospheric C Suess effect shifts skeletal δC > 1.0‰ lower. We also compiled coral δC from a global array of sites and find that mean coral δC decreases by -1.4‰ for every 5 m increase in water depth (R = 0.68, p < 0.01). This highlights the fundamental sensitivity of coral δC to endosymbiotic photosynthesis. Collectively, these results suggest that photosynthetic rate largely determines mean coral δC while changes in extension rate and metabolic effects over time modulate skeletal δC around this mean value. The newly quantified coral δC-water depth relationship may be an effective tool for improving the precision of paleo-sea level reconstruction using corals.
(Nature Communications. vol. 10, n° 2041-1723, pp. 2056, 27/04/2026)
LDEO, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ZMT
Declining maerl vitality and habitat complexity across a dredging gradient: Insights from in situ sediment profile imagery (SPI)
Maerl beds form complex biogenic benthic habitats, characterized by high productivity as well as diverse biological communities. Disturbances associated with extraction and/or fishing activities using mobile bottom-contacting gears such as clam-dredges induce the most severe and long-term effects on these fragile habitats. We here investigated the effects of dredge-fishing on maerl in the bay of Brest (France). We quantified maerl beds structure and vitality across a fine scale quantified dredging intensity gradient through the acquisition of in-situ images of beds cross-section using Sediment Profile Imaging system (SPI). Declines in the proxies of maerl vitality and habitat complexity were measured across the gradient, and were associated with significant changes in the vertical distribution of live and dead maerl as well as of interstitial space. Fishing with dredges caused maerl mortality, substratum compaction, and decreasing habitat complexity. SPI imaging techniques also allowed for an assessment of changes in spatial heterogeneity that dredging created on several aspects of the structure and vitality of maerl beds. It suggests that direct and indirect disturbances induced by dredging are not acting at the same spatial scale, and can thereby differentially affect the ecosystem functions linked to vitality and habitat complexity.
(Scientific Reports. vol. 9, n° 2045-2322, pp. 16463, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Application of the European Water Framework Directive: Identification of reference sites and bioindicator fish species for mercury in tropical freshwater ecosystems (French Guiana)
Mercury (Hg) is a toxic metal subject to several international regulations. The European Water Framework Directive (WFD) established in 2008 an Environmental Quality Standard for biota (EQSbiota) at 0.02 µg.g.
(Ecological Indicators. vol. 106, n° 1470-160X, pp. 14, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA