Extension of high temporal resolution sea level time series at Socoa (Saint Jean-de-Luz, France) back to 1875

In this data paper sea level time series at Socoa (Saint Jean-de-Luz, Southwestern France) is extended in a data archaeology exercise. We have catalogued water level records stored in ledgers and charts, as well as other associated documents (metadata) in thorough research of national and local archives. An extensive effort was made to rescue these documents by archiving them in digital formats. Based on this large set of rescued documents, the Socoa time series is further extended back in time by about 40 years, at hourly (for ledgers) to 5-minutes (for charts) sampling. Analysis of the precise levelling information reveals that the datum of the tide gauge site has been stable. We assessed the consistency of this new century-long time series based on nearby tide gauge data. Although the overall timeseries is generally consistent, siltation is found to be a recurrent problem of the stilling well which impacted some part of the extended data. However, being a high temporal resolution sea level time series spanning more than 100 years, this new dataset will be useful for advancing climate research, particularly the decadal scale variations in the North Atlantic, as well as the storminess and extreme events along the French Basque coastal region.</p

Environmental distribution and seasonal dynamics of Marteilia refringens and Bonamia ostreae, two protozoan parasites of the European flat oyster, Ostrea edulis

IntroductionMarteilia refringens and Bonamia ostreae are protozoan parasites responsible for mortalities of farmed and wild flat oysters Ostrea edulis in Europe since 1968 and 1979, respectively. Despite almost 40 years of research, the life-cycle of these parasites is still poorly known, especially regarding their environmental distribution.MethodsWe carried out an integrated field study to investigate the dynamics of M. refringens and B. ostreae in Rade of Brest, where both parasites are known to be present. We used real-time PCR to monitor seasonally over four years the presence of both parasites in flat oysters. In addition, we used previously developed eDNA based-approaches to detect parasites in planktonic and benthic compartments for the last two years of the survey.ResultsM. refringens was detected in flat oysters over the whole sampling period, sometimes with a prevalence exceeding 90%. It was also detected in all the sampled environmental compartments, suggesting their involvement in parasite transmission and overwintering. In contrast, B. ostreae prevalence in flat oysters was low and the parasite was almost never detected in planktonic and benthic compartments. Finally, the analysis of environmental data allowed describing the seasonal dynamics of both parasites in Rade of Brest: M. refringens was more detected in summer and fall than in winter and spring, contrary to B. ostreae which showed higher prevalence in winter and spring.DiscussionThe present study emphasizes the difference between M. refringens and B. ostreae ecology, the former presenting a wider environmental distribution than the latter, which seems closely associated to flat oysters. Our findings highlight the key role of planktonic and benthic compartments in M. refringens transmission and storage or potential overwintering, respectively. More generally, we provide here a method that could be useful not only to further investigate non cultivable pathogens life-cycle, but also to support the design of more integrated surveillance programs

Trois cents ans de mesures marégraphiques en France : outils, méthodes et tendances des composantes du niveau de la mer au port de Brest

Recent estimations show that the average sea level has risen up to about 20 cm over the last century, and even at a higher rate since 1993, (between 2.9 and 3.7 mm a year). This evolution will affect coastal populations and will create higher natural risks. Recently, sea level components have accordingly been the subject of numerous scientific studies, all the more as they are one of the best indicators to evaluate global warming. Studies show that it is necessary to process data time series longer than 60 years in order to infer significant trends for the sea level components. Observation and reconstitution of sea level fluctuations over the last centuries are at the heart of global warming research programs.Those estimations hide a large variability from one region to another. What about the French Atlantic coast? Has the sea level changed? When? How much? These questions will be answered in part II with the Brest tide gauge series, an exceptional data centre where systematic sea level measurements have been obtained since 1679!Prior to this work, however, one had to search in archives for all the possible old tide gauge data, the validation of which happened to be a quite difficult task. Hence, Part I first deals with the evolution of French sea level observations methods, both a prerequisite for targeting our old data research and a fundamental background to complete the contemporary observations series with the newly found old data.Les estimations récentes montrent que le niveau moyen de la mer a monté de quelque vingt centimètres au cours du siècle dernier avec un rythme supérieur depuis 1993 (entre 2,9 et 3,7 mm/an).Cette évolution aura un impact sur les populations côtières et sera à l'origine de risques naturels accrus. Ainsi les composantes du niveau marin font l'objet de nombreux travaux scientifiques d'autant qu'ils font partie des meilleurs indicateurs pour évaluer le réchauffement climatique. Les études montrent qu'il faut disposer de séries temporelles de mesures supérieures à 60 ans pour estimer des tendances fiables sur les composantes du niveau marin. L'observation et la reconstitution des fluctuations de ce niveau sur les derniers siècles s'inscrivent au coeur des grands programmes de recherche sur le réchauffement planétaire.Ces estimations masquent une grande variabilité d'une région à une autre. Qu'en est-il pour la côte atlantique française ? Le niveau moyen de la mer a-t-il évolué ? Quand ? De combien ? Autant de questions auxquelles nous allons tenter de répondre dans la partie II avec la série marégraphique de Brest, observatoire exceptionnel où des mesures systématiques du niveau de la mer sont réalisées depuis 1679 !Mais avant cela, il était nécessaire de rechercher toutes les données anciennes de marégraphie potentiellement encore en archives, et dont la validation devait se révéler difficile. La partie I traite alors de l'évolution des méthodes d'observation du niveau marin en France, préalable indispensable au ciblage de nos recherches de mesures anciennes, d'une part, et donnée fondamentale pour compléter les séries d'observations contemporaines par les mesures anciennes retrouvées, d'autre part

Trois cents ans de mesures marégraphiques en France (outils, méthodes et tendances des composantes du niveau de la mer au port de Brest)

Recent estimations show that the average sea level has risen up to about 20 cm over the last century, and even at a higher rate since 1993, (between 2,9 and 3,7 mm a year). This evolution will affect coastal populations and will create higher natural risks. Recently, sea level components have accordingly been the subject of numerous scientific studies, all the more as they are one of the best indicators to evaluate global warning. Studies show that it is necessary to process data time series longer than 60 years in order to infer significant trends for the sea level components. Observation and reconstitution of sea level fluctuations over the last centuries are at the heart of global warming research programs. Those estimations hide a large variability from one region to another. What about the French Atlantic coast? Has the sea level changed? When? How much? These questions will be answered in part II with the Brest tide gauge series, an exceptional data centre where systematic sea level measurements have been obtained since 1679! Prior to this work, however, one had to search in archives for all the possible old tide gauge data, the validation of which happened to be a quite difficult task. Hence, Part I first deals with the evolution if French sea level observations methods, both a prerequisite for targeting our old data research and a fundamental background to complete the contemporary observations series with the newly old data.LA ROCHELLE-BU (173002101) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF

REFMAR : une coordination pour l'observation du niveau de la mer

Le SHOM est le référent national pour l'observation, la gestion et la diffusion des mesures in situ du niveau de la mer. Cette fonction vise à coordonner les efforts des organismes réalisant l'acquisition de données du niveau de la mer sur le territoire national, dans un contexte où l'accès à ces données vise à répondre à des enjeux nationaux et internationaux, comme les programmes sur le suivi de l'évolution du niveau des mers (GLOSS) ou la montée en puissance des systèmes opérationnels de prévention des risques contre les submersions marines ou les tsunamis. Cette responsabilité conduit entre autres à s'intéresser au recueil et à l'archivage de l'ensemble des données de hauteur d'eau collectées et à leur diffusion au travers d'un portail Internet unique : REFMAR (pour réseaux de référence des observations marégraphiques) hébergé à l'adresse http://refmar.shom.fr. D'autres actions sont menées à bien pour remplir au mieux cette fonction comme la production d'un rapport annuel d'activité REFMAR, l'élaboration de fiches techniques plus particulièrement dédiées aux producteurs de données, la diffusion d'un calendrier fournissant tous les mois des informations pratiques sur la marégraphie et les grands coefficients de marée, la présence sur les réseaux sociaux : https://twitter.com/refmarshom et https://www.facebook.com/refmar.shom.fr... La tenue des premières journées REFMAR en juin 2013 a permis de réunir les acteurs majeurs du domaine, en particulier les producteurs d'observations de hauteurs d'eau et leurs usagers. Ce colloque a été l'occasion d'établir un état de l'art sur les applications de l'observation du niveau de la mer et de transmettre les bons usages sur cette mesure

Assessing the Influence of Changes in Shoreface Morphology since the 19th Century on Nearshore Hydrodynamics and Shoreline Evolution in Northern France: A Modeling Approach

The shoreface off the coast of northern France is characterized by the presence of numerous tidal sand banks, forming linear shore-parallel or slightly oblique massive sand bodies. Digitization of historic hydrographic field sheets from the French Hydrographic Service (Shorn) archives enabled to produce Digital Elevation Models (DEMs) of the seabed morphology at different dates since the early 19th century. Our analyses of bathymetry changes based on differential DEMs showed significant morphological variations across the shoreface near Calais during the 19th and 20th centuries, which are largely due to changes in nearshore sand bank morphology and position. Sand bank mobility can be partially explained by tidal current asymmetry, inducing an elongation and an alongshore migration of this sand body in the direction of the net residual tidal current. Observed changes in shoreface and nearshore morphology attempt to be related with possible variations in hydrodynamics, this paper presenting the results obtained on tidal currents. TELEMAC-2D model was used to simulate 2D velocity field and water depth during a spring and neap tidal cycle over bathymetry grids based on historical bathymetric soundings. Depending on the bathymetric setting, modeling of tidal residual currents revealed notable increases or decreases in residual current velocity during distinct time periods, particularly in nearshore areas, which may lead to seabed erosion where current strengthening is observed through titne or conversely to sediment accumulation in areas of decreasing current velocity. These results are consistent with the shoreline changes that occurred during the 20th century, with a correspondence between nearshore areas of decreasing (or increasing) residual current velocity and adjacent shorelines that were affected by seaward progradation (or erosion), suggesting strong links between changes in seabed morphology over the shoreface and shoreline evolution

Assessing the Influence of Changes in Shoreface Morphology since the 19th Century on Nearshore Hydrodynamics and Shoreline Evolution in Northern France: A Modeling Approach

International audienceThe shoreface off the coast of northern France is characterized by the presence of numerous tidal sand banks, forming linear shore-parallel or slightly oblique massive sand bodies. Digitization of historic hydrographic field sheets from the French Hydrographic Service (Shorn) archives enabled to produce Digital Elevation Models (DEMs) of the seabed morphology at different dates since the early 19th century. Our analyses of bathymetry changes based on differential DEMs showed significant morphological variations across the shoreface near Calais during the 19th and 20th centuries, which are largely due to changes in nearshore sand bank morphology and position. Sand bank mobility can be partially explained by tidal current asymmetry, inducing an elongation and an alongshore migration of this sand body in the direction of the net residual tidal current. Observed changes in shoreface and nearshore morphology attempt to be related with possible variations in hydrodynamics, this paper presenting the results obtained on tidal currents. TELEMAC-2D model was used to simulate 2D velocity field and water depth during a spring and neap tidal cycle over bathymetry grids based on historical bathymetric soundings. Depending on the bathymetric setting, modeling of tidal residual currents revealed notable increases or decreases in residual current velocity during distinct time periods, particularly in nearshore areas, which may lead to seabed erosion where current strengthening is observed through titne or conversely to sediment accumulation in areas of decreasing current velocity. These results are consistent with the shoreline changes that occurred during the 20th century, with a correspondence between nearshore areas of decreasing (or increasing) residual current velocity and adjacent shorelines that were affected by seaward progradation (or erosion), suggesting strong links between changes in seabed morphology over the shoreface and shoreline evolution