The French benthic newcomers: new records of Ampithoe valida S.I. Smith, 1873 and Polydora colonia Moore, 1907 in Brittany, first record of Bispira polyomma Giangrande & Faasse, 2012 in the North-East Atlantic and northernmost record of Prostheceraeus moseleyi Lang, 1884 in Europe
As introduced species constitute a major threat to biodiversity, it is crucial to properly monitor their spread to new regions. The present study reports new records of four species: 1) the amphipod Ampithoe valida S.I. Smith, 1873 and 2) the polychaete Polydora colonia Moore, 1907, both new records for Brittany (North-West part of France); 3) the polychaete Bispira polyomma Giangrande & Faasse, 2012, a first finding in the North-East Atlantic; and 4) the flatworm Prostheceraeus moseleyi Lang, 1884 with a confirmed northernmost record in North-East Atlantic. These species were recorded within two semi-enclosed bays: the Morbihan Gulf on the southern coast of Brittany and the Bay of Brest in the North-West part of Brittany. Both localities are already known to host numerous non-indigenous species as well as benthic macrofaunal distributional range limits. Morphological variations and inconsistencies are discussed and reported for A. valida, revealing missing characters and errors in the literature. This work adds three non-indigenous species to Brittany and two nonindigenous species to French waters, for which we discuss potential introduction vectors.
(BioInvasions Records. vol. 13, n° 2242-1300, pp. 37-56, 01/03/2024)
DYNECO, IFREMER, DECOD, IFREMER, INRAE, Institut Agro, Institut Agro, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OFB, LEMAR, IRD, IFREMER, UBO EPE, CNRS
Satellite observations of storm erosion and recovery of the Ebro Delta coastline, NE Spain
Storms and extremely energetic events may significantly impact the form and structure of beaches, and so cause erosive processes and coastal damages. Efficient management actions require an up-to-date and accurate knowledge of beach morphological changes, with the shoreline position being a good indicator of such changes. This work proposes the use of the open-source Shoreline Analysis and Extraction Tool (SAET) software for the definition of satellite-derived shorelines (SDSs) from L8 and Sentinel-2 imagery to reveal the shoreline position changes at the beaches of the Ebro Delta, NE Spain. Spatial-temporal models (STMs) of shoreline changes enable a characterisation of how the beaches responded to the storms of 2020. In conjunction with wave data, STMs enable an analysis of the erosive response to storm events, as well as a monitoring of subsequent beach recovery in the short and medium term (<1 year). Results show how Storm Gloria (January 2020, Hs max = 7.62 m) acted as a disruptive event and shifting point in the shoreline trend. As a response to that storm, major erosive processes occurred along the delta that caused an average shoreline retreat of 47 m. A progressive recovery during the spring and summer was mainly associated with periods of low wave energy. Nevertheless, by the end of the year a complete recovery had been achieved for about half of the coast, while the other half showed an average erosion of more than 10 m when compared to the pre-storm situation. Both the erosive and the recovery processes took place unevenly on different sections of the coast, probably dependent on factors such as the orientation of the beach and the pattern of longitudinal sediment transport along the coast.
(Coastal Engineering. vol. 188, n° 0378-3839, pp. 104451, 01/03/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
PHYTOBS-MARCOBOLO dataset – Phytoplankton time series in French coastal waters
The PHYTOBS-MARCOBOLO dataset comprises long-term time series on marine microphytoplankton, from 2003 to 2021, along the entire French metropolitan coastline. Microphytoplankton data cover microscopic taxonomic identifications and counts. The PHYTOBS-MARCOBOLO dataset corresponds to a dataset extracted from the PHYTOBS network (DOI:10.17882/85178). The PHYTOBS network provides the scientific community and stakeholders with validated and qualified data on the biomass, abundance and composition of marine microphytoplankton in coastal and lagoon waters, with the aim of supporting scientific research. PHYTOBS-MARCOBOLO is a dataset used as part of the Horizon Europe MARCO-BOLO project (https://marcobolo-project.eu/), in which we are currently working to understand and analyze multi-decadal trends in coastal and marine biodiversity on a European scale. The PHYTOBS-MARCOBOLO dataset gathers data from 18 sampling sites, selected from the PHYTOBS-Network dataset according to requirements of time series quality and geographical location of sampling sites established as part of the MARCO-COLO project. This dataset was also formatted according to a template imposed for the European project.
(27/02/2024)
ECLA, USMB [Université de Savoie] [Université de Chambéry], INRAE, OFB, CARRTEL, USMB [Université de Savoie] [Université de Chambéry], INRAE, Fédération OSUG, UNICAEN, NU, CREC, UNICAEN, NU, DOI, IFREMER, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO, AP-HP, LERBL, COAST, IFREMER, PHYTOX, IFREMER, LERBO, COAST, IFREMER, LOMIC, INSU - CNRS, SU, CNRS, OOB, SU, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, LIRTES, UPE, UPEC UP12, IHPE, UPVD, IFREMER, CNRS, UM, LERBN, COAST, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, IFREMER
Reconstitution des conditions hydrographiques néritiques à l’échelle du Golfe de Gascogne au cours du dernier millénaire : apports de l'étude croisée de la vasière ouest-Gironde et des littoraux bretons
Les archives sédimentaires holocènes, prélevées en contexte de plateforme, offrent une vision pluri-séculaire permettant de reconstruire l’impact des variations climatiques sur les environnements de la marge métropolitaine atlantique en s’éloignant de la période Anthropocène. C’est particulièrement le cas du dernier millénaire avec la succession de trois périodes climatiques marquées : la Période Chaude Médiévale (PCM ; i.e. Warm Medieval period) jusqu'à 1400 A.D., le dernier analogue à la PCM, la période de réchauffement récente (RC ; i.e. Recent Warming) à partir de 1800 A.D., et le refroidissement du Petit Age Glaciaire (PAG ; i.e Little Ace Age, LIA) entre les deux. Ce travail vise donc à reconstruire les forçages hydrologiques et hydrosédimentaires des derniers 600 ans au niveau de deux secteurs clés de la façade Atlantique française : la Vasière Ouest-Gironde (VOG) et les littoraux bretons (Grande Vasière et rade de Brest). La VOG, intégrée au projet OFB-TRESSE (TRajectoires-EStuaires–Sediments), a été carottée lors de la mission JERICOBENT-7 (juillet 2019, N/O Côtes de la Manche, Deflandre, 2019 ; projet interface EC2CO-LEFE; 2018-2022), permettant l’acquisition de nouvelles séquences sédimentaires (carottes JB7ST3c, JB7ST3). Ces carottes ont fait l’objet d’une étude multi-indicateurs, incluant notamment des analyses palynologiques marines (kystes de dinoflagellés), sédimentologiques et géochimiques semi-quantitatives (XRF). Une étude haute-résolution des assemblages phytoplanctoniques a pu être menée sur la carotte JB7ST3, dominée par une sédimentation fine et continue. Un changement significatif des assemblages de dinokystes ainsi que des apports sédimentaires enrichis en éléments terrigènes pendant le PAG sont mis en évidence. Les résultats XRF ont permis de définir de nouveaux ratios élémentaires tels que Zr/Br (i.e., signal granulométrique « haute-résolution ») et Ca/Y (productivité carbonatée). La comparaison de ces nouveaux descripteurs aux rapports classiquement utilisés dans d’autres environnements sédimentaires (marges, lacs, tourbières) permet d’envisager de nouvelles pistes pour mieux appréhender la complexité des milieux de plateforme. Nos résultats suggèrent un contrôle climatique majeur sur les apports sédimentaires et les conditions hydrologiques de surface (températures, salinités), voire même sur la productivité océanique avec un début d’eutrophisation noté à partir de la fin du 18ème siècle. Les résultats inédits issus de l’étude des carottes de la VOG ont ensuite été comparés à ceux récemment obtenus dans le nord de la Grande Vasière sur la carotte CBT-CS11 (sud Finistère, alimentation détritique principale liée aux apports de la Loire et dans une moindre mesure de la Gironde ; Penaud et al., 2020 ; David et al., 2022) et dans la Rade de Brest sur la carotte I-09 (Ouest Finistère, baie estuarienne macro-tidale; Klouch et al., 2016 ; Lambert et al., 2018 ; Valero et al., in prep). La comparaison des données de la VOG avec les archives sédimentaires du secteur breton (Grande Vasière et rade de Brest) nous permet d’avancer des hypothèses sur les changements hydrologiques et hydrosédimentaires au cours du dernier millénaire. Les signaux obtenus sont pluriels, montrant des réponses parfois semblables, parfois contrastées. Néanmoins, les impacts anthropiques, détectés par des augmentations de productivité, sur les trois sites semblent synchrones.
(26/02/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS
Forest expansion during Heinrich stadial 6: Data-model comparison of a new southeastern France pollen record
Reconstructing past climate and environment is key to understand the relationship between prehistoric humans and their environment, specially throughout the Heinrich 6 stadial (HS 6, ca. 64-60 ka). In Europe, the HSs are all characterized by steppe expansions, but the new pollen analysis of the marine sedimentary core collected in the Gulf of Lion (MD99-2343) documents another scenario with an increase in forest cover during HS 6. An ensemble of pollen-climate calibration models will quantitatively reconstruct temperature and precipitation. The reconstruction ensemble employs a classical reconstruction method (MAT, WA, and MLRC) complemented by the recently developed fxTWA-PLS transfer function, as well as machine learning approaches (RandomForest, BRT). We interpret the unexpected forest development during HS 6 as the result of the combination of precession minima and a local atmospheric-oceanic process in the Gulf of Lion related to the instability of the Laurentian ice-sheet. To further investigate the process underlying the vegetation response to HS 6, we will perform a Heinrich-type simulation using the intermediate complexity coupled climate model iLOVECLIM with freshwater inputs.
(26/02/2024)
UB, UBM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB, EPHE, PSL
A deep reservoir for hydrogen drives intense degassing in the Bulqizë ophiolite
Deep crustal production of hydrogen (H 2 ) is a potential source of primary energy if recoverable accumulations in geological formations are sufficiently large. We report direct measurements of an elevated outgassing rate of 84% (by volume) of H 2 from the deep underground Bulqizë chromite mine in Albania. A minimum of 200 tons of H 2 is vented annually from the mine’s galleries, making it one of the largest recorded H 2 flow rates to date. We cannot attribute the flux solely to the release of paleo-fluids trapped within the rocks or to present-day active and pervasive serpentinization of ultramafic rocks; rather, our results demonstrate the presence of a faulted reservoir deeply rooted in the Jurassic ophiolite massif. This discovery suggests that certain ophiolites may host economically useful accumulations of H 2 gas.
(Science. vol. 383, n° 0036-8075, pp. 618-621, 09/02/2024)
ISTerre, IRD, INSU - CNRS, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, UGA, AKBN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Assessing Satellite-Derived Shoreline Detection on a Mesotidal Dissipative Beach
The accuracy and robustness of the shoreline definition from satellite imagery on different coastal types are crucial to adequately characterising beach morphology and dynamics. However, the generic and widespread application of satellite-derived shoreline algorithms is limited by the lack of robust methods and parameter assessments. This work constitutes a quantitative and comprehensive assessment of the satellite-derived waterlines from Sentinel-2 by using the novel SAET tool (Shoreline Analysis and Extraction Tool) on the exposed and mesotidal beach of La Victoria (Cádiz, SW Spain). The diverse parameters available in SAET, such as water indexes, thresholding methods, morphological filters, and kernel sizes, were combined to define water/land interface positions that were compared against coincident video-derived waterlines. Satellite-derived waterline errors are found to be affected by extraction parameters, as well as by the oceanographic and morphological conditions at the time of the image acquisition. The application of a morphological erosion filter on the water mask, which tends to shift the extracted waterline seawards and reduce bias, is the best solution at the dissipative site of La Victoria Beach. Moreover, using a 3 × 3 kernel size consistently shows higher accuracies than a larger kernel. Although there was no parameter combination showing the best skill for all dates, the employment of the Automated Water Extraction Index for images with no shadows (AWEInsh) with a threshold = 0, erosion morphological filter, and 3 × 3 kernel was, overall, the best combination of extraction parameters for this beach (average waterline RMSE of 5.96 m). The combination of the Modified Normalised Difference Water Index (MDNWI) with the Otsu thresholding also led to similar positions of the resulting waterlines and offered good accuracies. In line with other recent research efforts, our work stresses the lack of generic shoreline extraction solutions that can be applied automatically at a global level and the necessity to adapt and validate the extraction methodologies to the different types of coastlines.
(Remote Sensing. vol. 16, n° 2072-4292, pp. 617, 07/02/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The role of surfers in beach safety management: Insights from French respondents to a global surfer survey
Coastal locations are a leading contributor to the global drowning burden. Despite being a known risk-reduction measure, a significant proportion of beachgoers continue to bathe outside of lifeguard-patrolled areas placing themselves at increased risk of beach hazards such as rip currents and breaking waves. Under such conditions, recreational surfers represent a potentially important role as bystander rescuers although little is known about surfers' relationship to safety. In this study, we analyze surfer beach safety knowledge and behaviors using a sample of 569 French surfers, drawn from a Global Surfer Survey. Using pair wised comparisons and multivariate analysis, surfer characteristics as rescuers and as victims are investigated as well as their willingness to learn new safety skills. In our survey, 55.9% of French surfers self reported having previously conducted a rescue. We show that experienced and highly skilled surfers have a higher probability of performing a rescue than other surfers, but having completed ocean lifeguard training has no statistical influence. Having previously experienced injury seems beneficial both to act as a rescuer, but also in improving a surfers own safety. As victims, surfers appear to be calmer and less often in trouble with rip currents as others, such as swimmers. Compared to non surfers, surfers were less likely to be able to walk away and more likely to require medical assistance nevertheless. In the survey, 88.4% of the respondents were willing to take part in a course aimed at lifesaving and rescue skills for surfers, whether freely provided or not. Younger surfers (under 24 years) are more willing to acquire formal safety skills than other age groups. On the contrary, having alreadly performed a rescue has no statistical influence on the willingness to attend training sessions. Despite the significant involvement of surfers in saving lives in the coastal environment, there remains a need to encourage collaboration between local surfers and other stakeholders officially in charge of beach safety management.
(Ocean and Coastal Management. vol. 248, n° 0964-5691, 01/02/2024)
UR ETTIS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
On the role of hydrodynamic and morphologic variables on neural network prediction of shoreline dynamics
Predicting shoreline change is a key issue in coastal research. Predictors, process-based or data-driven, tend to be developed and tested on high-frequency and high-quality data sets. Combining hydrodynamic and morphological variables extracted from video images and artificial neural network allows us to evaluate if sparse data could still provide physically-sound shoreline change predictions. The data set covered a 3-year period with shoreline position data (with an accuracy of ±5 m) available 73 % of the time and 66 % for the morphological parameters (beach state or bar location). The best configuration of the trained shallow (one hidden layer) Feedforward Artificial Neural Network (ANN), includes 10 input variables and 10 nodes allowing to capture the shoreline dynamic at different time scales, from the storm-event to the seasonal scale, and to predict the shoreline position on a 1-year period with a RMSE of about 6.7 m. Increasing the complexity of the architecture of the ANN by increasing the number of hidden layers did not improve the predictions. By modifying the number of input variables in the algorithm, the ANN also allows us to highlight the mitigation effect of the bar during the storm event and its role as sediment buffer during seasonal accretion.
(Geomorphology, n° 0169-555X, 01/02/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, LEESA, UB, CNRS
Persistent organic pollutants and trace metals in selected marine organisms from the Akanda National Park, Gabon (Central Africa)
Akanda National Park (ANP) is composed of mangrove ecosystems bordering Libreville, Gabon's capital. The contamination of aquatic resources from the ANP by persistent organic pollutants (POPs) and trace metals (TMs) was never evaluated. To provide a basis for their monitoring in the ANP, five species (two fish, two mollusks, and one crustacean) were analyzed from three sampling sites in 2017. Contamination levels for POPs and TMs were below maximum acceptable limits for seafood, including Cd and Pb. No DDT was found in any sample. Inter-specific differences were more obvious than the differences among sites, although the results may be biased by an unbalanced sampling design. The oyster Crassostrea gasar was the most contaminated species, making this species a good candidate to assess environmental contamination in the area. The studied species also contained essential elements, such as Fe, Zn and Mn at interesting levels in a nutritional point of view.
(Marine Pollution Bulletin. vol. 199, n° 0025-326X, pp. 116009, 01/02/2024)
IRD, LEMAR, IRD, IFREMER, UBO EPE, CNRS, SFA, SOS, CENAREST, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR MARBEC, IRD, IFREMER, CNRS, UM