Multiple genetic marker analysis challenges the introduction history of Ulva australis (Ulvales, Chlorophyta) on French coasts

The three main estuaries in the French Atlantic coast – the Seine, Loire and Gironde, all with high tidal regimes – are interfaces between the continental and the coastal ecosystems. The Seine and Gironde are highly contaminated, whereas the Loire remains in a more natural state. Both the Seine and Gironde have suffered from harbour construction, and as a result, their biological units are extremely compartmentalized. Benthic species and communities have adapted to tolerate temporal physical and chemical changes (e.g. salinity, substrata, depth, and levels of fine particles and oxygen) and human activities (e.g. dredging, shipping traffic, and habitat reduction). Although numerous bio‐indicators and indices are used to define the ecological quality status (EcoQS) of coastal waters, very few of them were developed specifically for environments with a mosaic of conditions and salinity levels, including freshwater. The main problem appears to be that all the indices for determining anthropogenic stress examine the abundances of stress‐tolerant species, which may also be able to tolerate natural stressors such as those occurring in estuaries. This paper takes a look at the development status of the benthic indicators and index approaches used in the three main estuaries along the French Atlantic coast. In addition, it examines the adaptation of the different benthic indicators to the taxonomic sufficiency principle, and the adaptation of the Benthic Opportunistic Polychaetes Amphipods index (BOPA) and the Benthic Opportunistic Annelida Amphipod index (BO2A) for use in the freshwater zones of transitional waters (i.e. up to the upper limit of the tidal range). Several perspectives are discussed in light of the diverse disturbances and the heterogeneity of such stressed zones, such as the use of multimetric and scoring approaches.

Marine biofouling communities, including biofilms, are composed of many eukaryotes with high taxonomic and functional diversities. However, molecular characterization of eukaryotic diversity of marine biofouling has been barely developed due to the only recent interest in research areas such as marine renewable energies, antifouling technologies, or plastic pollution. The aim of this study was to compare the diversity and taxonomic composition of biofouling through different metabarcoding approaches used to detect the widest range of taxa from samples collected in several contrasted marine environments (French Atlantic and Mediterranean coasts). Thus, we assessed four DNA extraction methods and six primers pairs targeting the 18S rDNA gene (including the V1-V2, V4TAR, V4UNI, V7 and V9 regions) and the COI gene, the latter with two databases (BOLD and MIDORI). In addition the influence of primers selection was analyzed at three sites to compare geographic variations in eukaryotic diversity. Although none of the extraction methods greatly altered the community diversity or composition. we have observed that eukaryotic biofouling community diversity and structure varied depending on primers pairs, reference databases and sites. 18S rDNA regions allowed the detection of more taxa at the species level, including microeukaryotes, while the COI recovered more ASVs, but with a large proportion that remained taxonomically unassigned probably because BOLD and MIDORI specifically targeted metazoans. Interestingly, the spatial pattern obtained with both COI and 18S rDNA markers were similar showing that spatial selection occurred throughout a wide diversity of eukaryotic taxa. These results encouraged the use of these two complementary markers for future metabarcoding investigations but also highlighted the relevance of completing databases to enhance the identification of biofouling eukaryotes.

Tolypella salina R. Cor. is a Charophyte only known from some French and Iberian stations. Its rarity and the specific richness of the salt marshes where it grows, on the Atlantic and Mediterranean coasts, have led to the proposal to add this species to the French list of protected plants. A survey of stations was realized on the Atlantic coast (Noirmoutier, Guérande) between 2010 and 2013 to complete the distribution map of this taxon. The aim of this work is to improve the knowledge of this plant’s biology and its ecological environment. It appears that the development of this species differs between stations, and also from one year to the next, a phenomenon due to the instability of its living environment (hydrological and salinity conditions, etc.). Phytosociological considerations related to the subassociation tolypelletosum salinae are added. Some recommendations are proposed for the management of these sites, taking into account the human activities there, in order to maintain the salt marsh mosaic that is necessary for the conservation of Tolypella salina.

During 1994 net sediment-water fluxes of oxygen, ammonium and inorganic phosphorus as well as sediment profiles of organic matter, nitrogen, phosphorus and iron were determined in three shallow eutrophic environments. Investigations were conducted monthly from March to December at five stations in the Sacca di Goro (Po River Delta, Italy). In the late summer, samples were collected from a single site in the Prevost lagoon (French Mediterranean coast) and three stations in the Bassin d’Arcachon (French Atlantic coast). In the Sacca di Goro, water-sediment exchanges of O2, NH 4 + and PO 4 3- were estimated by means of core incubation in the dark. Benthic fluxes for the French lagoons were in part determined experimentally using benthic chambers and in part from the literature.

Field surveys have reported a global shift in harbour porpoise distribution in European waters during the last 15 years, including a return to the Atlantic coasts of France. In this study, we analyzed genetic polymorphisms at a fragment of the mitochondrial control region (mtDNA CR) and 7 nuclear microsatellite loci, for 52 animals stranded and by-caught between 2000 and 2010 along the Atlantic coasts of France. The analysis of nuclear and mitochondrial loci provided contrasting results. The mtDNA revealed two genetically distinct groups, one closely related to the Iberian and African harbour porpoises, and the second related to individuals from the more northern waters of Europe. In contrast, nuclear polymorphisms did not display such a distinction. Nuclear markers suggested that harbour porpoises behaved as a randomly mating population along the Atlantic coasts of France. The difference between the two kinds of markers can be explained by differences in their mode of inheritance, the mtDNA being maternally inherited in contrast to nuclear loci that are bi-parentally inherited. Our results provide evidence that a major proportion of the animals we sampled are admixed individuals from the two genetically distinct populations previously identified along the Iberian coasts and in the North East Atlantic. The French Atlantic coasts are clearly the place where these two previously separated populations of harbour porpoises are now admixing. The present shifts in distribution of harbour porpoises along this coast is likely caused by habitat changes that will need to be further studied.

Summer mass blooms of macroalgae have been occurring increasingly for two decades along the French Atlantic coastline (Fig. 9.1). The coasts of Brittany are the most affected, considering the nearly 100 000 m3 of green seaweeds collected yearly from the beaches. One member of the genus Ulva is particularly involved in these mass blooms, although some ectocarpales, for example Pilayella littoralis, recently appeared in some localities.

Classification of unitemporal and multitemporal LANDSAT data by the transformation of Karhunen-Loeve. Application to l'Anse de l'Aiguillon (French atlantic coast). This paper is concerned with automatic classification of Landsat remotely sensed data. A non-supervised simple method is first developed. Afterwards, principal component analysis is applied to a single data scene and then to several data scenes. In this latter case, land cover (scene content) is defined according to diachronic variation of digital counts. The example chosen to demonstrate this technique is Anse de l'Aiguillon, on the French Atlantic coast, where topographic features are irrelevant to the pixel values of local landscape (water, tidal flat, salt marsh and polders).

The concentration of Pb and its stable isotope composition were measured in 216 composite samples of 50 blue mussels (Mytilus edulis (M. edulis)) collected quarterly between 1985 and 2005 at three sites along the French Atlantic coast, one in the La Fresnaye Bay and the others in the Loire and Seine River estuaries. Depending on the sites and time periods, Pb concentrations were 5-66 times higher than the natural background value for the North Atlantic. Even for the samples with the lowest Pb concentrations, the isotopic signature of Pb is very different than that of the regional natural Pb, suggesting that most of the bioaccumulated Pb is anthropogenic in origin. Stable Pb isotope ratios measured in the mussels differ markedly from that of Pb emitted in Western Europe as a result of leaded gasoline combustion, which was still a dominant source of contaminant Pb to the atmosphere during most of our study period. The isotope composition of Pb in the mussels was instead more typical of that of the Pb released to the environment by wastewater treatment plants, municipal waste incinerators, and industries such as metal refineries and smelters. Continental runoff, rather than atmospheric deposition, is therefore identified as the leading transport pathway of Pb along the French Atlantic coast. From the strong seasonal variations in (206)Pb/(208)Pb ratios in the mussels from the Seine Estuary site we also conclude that the resuspension of contaminated sediments, triggered by high river runoff events, is a chief factor affecting the bioaccumulation of Pb in M. edulis . The value of this organism as a biomonitor of coastal contamination is thus further demonstrated.

Observations have been made on the biology of two species of the bivalve genus Donax, on two beaches, Vertbois and St. Trojan, on the Ile d'Oleron, French Atlantic coast. The two species displayed different vertical distribution: D. trunculus Linne in the intertidal; and D. vittatus (da Costa) between low-water spring tide (LWST) and 5 to 6m depth, with only the fringe of the population extending to the shore. D. trunculus also showed differential distribution by size or age, the youngest individuals being highest on the shore, and the oldest near LWST. The two species exhibited a similar pattern of seasonal recruitment and growth, but in both there were differences in growth characteristics between the two beaches, individuals at St. Trojan growing to a larger size than those at Vertbois. The mean pattern of mortality in the two areas was similar, and productivity per 100 recruits surviving to the first winter following settlement was greater at St. Trojan than at Vertbois. For D. trunculus the mean population density at Vertbois was higher and the production per unit area on the two beaches was similar. Production to biomass (B) and elimination to biomass (B) ratios were similar for the two beaches for both species, and while production was greater for D. trunculus at both beaches, the B and B ratios were higher for D. vittatus. Comparisons with other published data reveal that the rate of growth of D. trunculus is similar throughout its range from Brittany to the Mediterranean Sea, while that of D. vittatus shows more variation. In both species, there is a trend of increasing P/B and E/B ratios from north to south throughout the geographical range.

In an analysis of the population genetics of the tiny meiofaunal polychaete Hesionides gohari, the RAPD-PCR method was applied to 49 specimens from 7 collecting sites far apart on three continents: French Atlantic coast, Mediterranean (Majorca, Giglio, Crete), Red Sea, Indian Ocean (Phuket), and U.S. Atlantic coast (Florida). In the band patterns produced with 14 arbitrary decamer primers, 496 genetic characters were detected. Genetic distances between the H. gohari populations vary between 0.55 and 0.70. The data were evaluated by three cluster programs; in the almost congruent phenograms, three clades were found with high bootstrap values: (1) European Atlantic-Mediterranean-Red Sea, (2) Indian Ocean, (3) Western Atlantic. In all cluster analyses, Hesionides riegerorum from a U.S. east coast river system is shown as genetically nearest to the Florida specimens of H. gohari, making it most probable that this freshwater species of the genus originated from a Western Atlantic H. gohari population. The genetic distances detected between the H. gohari specimens from the three continents are almost identical to those found between morphologically similar interstitial polychaete species pairs. Thus, the degree of genetic consistency is considered not to be high enough to corroborate the notion of a cosmopolitan distribution pattern, but rather suggests that the three clades represent different species.

Foraminiferal mudflat communities in the Auray estuary, located along the French Northwest Atlantic coast, were investigated in September 2020. Numerous living specimens of calcareous species showed marks of dissolution. The number of affected individuals, together with their dissolution degree, varied from one site to another. Moreover, pH profiles showed porewater acidification of the subsurface sediment at several stations. We propose two metrics quantifying the degree of dissolution: (i) the “Foraminiferal Test Dissolution” (FTD), based on binocular observations of the foraminiferal community, and (ii) the “Calcareous Test Preservation Ratio” (CTPR), surface ratio (0–0.5 cm) of total living foraminiferal densities (0–1 cm). In stations showing sediment acidification, the O 2 -pH profiles show the typical biogeochemical signatures of cable bacteria activity (pH increase in the oxic zone followed by strong acidification in the suboxic zone). This suggests that bacterial activity could be responsible for the strong pH decrease leading to corrosive porewaters affecting calcareous tests, hence severe FTD in the first centimetre of sediment leading to high CTPR. Furthermore, observations of FTD in other estuaries on the French Atlantic coast indicate that the phenomenon has become widespread. Re-investigated foraminiferal tests sampled in 1995–1996 in the Auray estuary show no dissolution marks, suggesting that the dissolution process observed in 2020 appeared over the last thirty years. Therefore, the FTD and CTPR could be used as rapid tools to establish the occurrence of dissolution processes, pending geochemical confirmation. The FTD could also be used as sediment acidification proxy in historical records, where geochemical analyses are not possible.

In the last ten years, 14 species of cetaceans and five species of pinnipeds stranded along the Atlantic coast of Brittany in the North West of France. All species included, an average of 150 animals strand each year in this area. Based on reports from the stranding network operating along this coast, the most common stranding events comprise six cetacean species (Delphinus delphis, Tursiops truncatus, Stenella coeruleoalba, Globicephala melas, Grampus griseus, Phocoena phocoena)and one pinniped species (Halichoerus grypus). Rare stranding events include deep-diving or exotic species, such as arctic seals. In this study, our aim was to determine the potential contribution of DNA barcoding to the monitoring of marine mammal biodiversity as performed by the stranding network.We sequenced more than 500 bp of the 5’ end of the mitochondrial COI gene of 89 animals of 15 different species (12 cetaceans, and three pinnipeds). Except for members of the Delphininae, all species were unambiguously discriminated on the basis of their COI sequences. We then applied DNA barcoding to identify some “undetermined” samples. With again the exception of the Delphininae, this was successful using the BOLD identification engine. For samples of the Delphininae, we sequenced a portion of the mitochondrial control region (MCR), and using a non-metric multidimentional scaling plot and posterior probability calculations we were able to determine putatively each species. We then showed, in the case of the harbour porpoise, that COI polymorphisms, although being lower than MCR ones, could also be used to assess intraspecific variability. All these results show that the use of DNA barcoding in conjunction with a stranding network could clearly increase the accuracy of the monitoring of marine mammal biodiversity.

Navicula spartinetensis Sullivan et Reimer was originally described from the sediments of a Delaware salt marsh on the east coast of the USA in 1975. This diatom species was first reported from Europe in the Dangast (North Sea) tidal flat sediments using this specific epithet some 30 years later. Further studies have led to its identification in collections from the Atlantic coast of France, the Tagus Estuary in Portugal, the Netherlands, Germany and Denmark. A search for illustrations of this species in the available literature on the diatom flora of European coasts was unsuccessful. However, our study of material collected in 1957 from the French Atlantic coast indicates that N. spartinetensis was present in Europe before its formal description. It is likely that N. spartinetensis has been included under the name N. flanatica Grunow in previous studies. No specific statements can be made concerning its biogeography because of the scarcity of floristic studies in marine coastal environments. It appears that at present N. spartinetensis has been collected from the USA and Europe in muddy, estuarine intertidal sediments with or without a vascular plant cover.

<p>The estimation of the sea levels with a high return period is crucial for coastal planning and the assessment of coastal flooding risk. Coastal facilities are designed to very low probabilities of failure and hence the design values are affected by significant uncertainties. Some recent coastal floods due to exceptional surges suggest that the design performed with the current statistical approaches may sometimes be significantly underestimated. This presentation is a contribution to the use of historical observations to improve the estimation of extreme sea levels. Historic records consist in observed major sea level values. The corresponding skew surges may be estimated but the exhaustiveness of historical skew surges, which is an essential criterion for an unbiased statistical inference cannot be guaranteed. . Indeed, Extreme skew surges can easily remain unnoticed if they occur at low or moderate high tide and do not generate extreme sea levels. This study proposes to combine, in a single Bayesian inference procedure, series of measured skew surges for the recent period and extreme sea levels for the historic period. The method is tested on four sites (tide gauges) located on the French Atlantic and Channel coasts. The proposed method appears to provide unbiased quantile estimates and to be more reliable than previously proposed approaches to include historic records in coastal sea level or surge statistical analyses.</p>

Émissions sonores enregistrées en marais salé et attribuées à l'anguille européenne