Long-term variability and environmental preferences of calycophoran siphonophores in the Bay of Villefranche (North-Western Mediterranean)

Long-term variability of the main calycophoran siphonophores was investigated between 1974 and 1999 in a coastal station in the north-western Mediterranean. The data were collected at weekly frequency using a macroplankton net (680 μm mesh size) adapted to quantitatively sample delicate gelatinous plankton. A 3-year collection (1967–1969) of siphonophores from offshore waters using the same methodology showed that the patterns of variability observed inshore were representative of siphonophores’ changes at a regional scale. The aims of the study were: (i) to investigate the patterns of variability that characterised the dominant calycophoran species and assemblages; (ii) to identify the environmental optima that were associated with a significant increase in the dominant siphonophore species and (iii) to verify the influence of hydroclimatic variability on long-term changes of siphonophores. Our results showed that during nearly 3 decades the standing stock of calycophoran siphonophores did not show any significant change, with the annual maximum usually recorded in spring as a result of high densities of the dominant species Lensia subtilis, Muggiaea kochi and Muggiaea atlantica. Nevertheless, major changes in community composition occurred within the calycophoran population. Since the middle 1980s, M. kochi, once the most dominant species, started to decrease allowing other species, the congeneric M. atlantica and Chelophyes appendiculata, to increasingly dominate in spring and summer–autumn, respectively. The comparison of environmental and biotic long-term trends suggests that the decrease of M. kochi was triggered by hydrological changes that occurred in the north-western Mediterranean under the forcing of large-scale climate oscillations. Salinity, water stratification and water temperature were the main hydroclimatic factors associated with a significant increase of siphonophores, different species showing different environmental preferences.

[Mâcon], équipe [de] Villefranche-Lyon, championnats de France [d'aviron, 15/8/20] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 60520

« La prinse et delivrance du roy (François Ier), venue de la royne (Éléonore) seur aisnée de l'empereur (Charles Quint) en France, et recouvrement de messeigneurs les daulphin et duc d'Orléans », par « SERASTIEN MOREAU, de Villefranche en Beaujoloys, refferendaire general du duché de Millan ».

L'ouvrage commence (fol. 13) par : « Comme après le trespas de très haulte et très puissante princesse madame Anne de France... » et finit (fol. 258) par : «... le langaige mal aorné cueilly de ma nativite beaujoloyse, qui en fera l'excuse. Finis. Quant ce sera ». Il est précédé (fol. 1-10) premièrement d'une dédicace à « maistre Gilbert Bayart, conseiller du roy nostre sire, notaire et secretaire de ses finances », secondement, d'une autre dédicace à « hault et puissant seigneur messire Anne de Montmorency, chevalier de l'ordre du roy, seigneur dudit lieu, premier baron de l'Isle de France, mareschal et grant maistre », datée de Lyon, ce premier jour de janvier l'an mil cinq cens trente et ung » et suivies d'un prologue, dont les premiers mots sont : « Pour ce que depuys l'an mil troys cens cinquante... ». En différents endroits sont des corrections ou additions. Aux fol. 261-263 est une lettre de l'auteur à « François de Herville, notaire et secretaire du roy... commissaire des morte-payes de Guyenne », son frère, dans laquelle il lui annonce l'envoi de son ouvrage, et lui demande de le revoir, pour après le présenter à Gilbert Bayart. La fin du volume (fol. 265-284) est remplie par deux listes des évêchés et archevêchés du royaume, l'une pour la cotisation du clergé, l'autre pour la cotisation de la noblesse dans la contribution destinée à payer la rançon du roi François Ier et le « recouvrement » des dauphin et duc d'Orléans, ses enfants, prisonniers en Espagne. Sébastien Moreau, qui avait été chargé de la levée des décimes du clergé en Limousin, se proposait d'indiquer les sommes auxquelles les différents évêchés avaient été texés et les sommes reçues. Aucun chiffre n'y a malheureusement été mis. On a ajouté en tête du ms. (fol. A et B) une note, écrite au XVIIIe siècle, sur l'intérêt que présente cet ouvrage.

Villefranche MedSeA mesocosm experiment 2013: perturbation studies and field studies

A joint mesocosm experiment took place in February/March 2013 in the bay of Villefranche in France as part of the european MedSeA project. Nine mesocosms (52 m**3) were deployed over a 2 weeks period and 6 different levels of pCO2 and 3 control mesocosms (about 450 µatm), were used, in order to cover the range of pCO2 anticipated for the end of the present century. During this experiment, the potential effects of these perturbations on chemistry, planktonic community composition and dynamics including: eucaryotic and prokaryotic species composition, primary production, nutrient and carbon utilization, calcification, diazotrophic nitrogen fixation, organic matter exudation and composition, micro-layer composition and biogas production were studied by a group of about 25 scientists from 8 institutes and 6 countries. This is one of the first mesocosm experiments conducted in oligotrophic waters. A blog dedicated to this experiment can be viewed at: http://medseavillefranche2013.obs-vlfr.fr.

Time series of ZOOSCAN images and results of zooplankton samples at Villefranche from 1966 to 2003

ZooScan with ZooProcess and Plankton Identifier (PkID) software is an integrated analysis system for acquisition and classification of digital zooplankton images from preserved zooplankton samples. Zooplankton samples are digitized by the ZooScan and processed by ZooProcess and PkID in order to detect, enumerate, measure and classify the digitized objects. Here we present a semi-automatic approach that entails automated classification of images followed by manual validation, which allows rapid and accurate classification of zooplankton and abiotic objects. We demonstrate this approach with a biweekly zooplankton time series from the Bay of Villefranche-sur-mer, France. The classification approach proposed here provides a practical compromise between a fully automatic method with varying degrees of bias and a manual but accurate classification of zooplankton. We also evaluate the appropriate number of images to include in digital learning sets and compare the accuracy of six classification algorithms. We evaluate the accuracy of the ZooScan for automated measurements of body size and present relationships between machine measures of size and C and N content of selected zooplankton taxa. We demonstrate that the ZooScan system can produce useful measures of zooplankton abundance, biomass and size spectra, for a variety of ecological studies.

Villefranche sur Mer: multistressors experiment March 2012

The effect of ocean warming and acidification was investigated on a natural plankton assemblage from an oligotrophic area, the bay of Villefranche (NW Mediterranean Sea). The assemblage was sampled in March 2012 and exposed to the following four treatments for 12 days: control ( 360 µatm, 14°C), elevated pCO2 ( 610 µatm, 14°C), elevated temperature ( 410 µatm, 17°C), and elevated pCO2 and temperature ( 690 µatm, 17°C). Nutrients were already depleted at the beginning of the experiment and the concentrations of chlorophyll a (chl a), heterotrophic prokaryotes and viruses decreased, under all treatments, throughout the experiment. There were no statistically significant effects of ocean warming and acidification, whether in isolation or combined, on the concentrations of nutrients, particulate organic matter, chl a and most of the photosynthetic pigments. Furthermore, 13C labelling showed that the carbon transfer rates from 13C-sodium bicarbonate into particulate organic carbon were not affected by seawater warming nor acidification. Rates of gross primary production followed the general decreasing trend of chl a concentrations and were significantly higher under elevated temperature, an effect exacerbated when combined to elevated pCO2 level. In contrast to the other algal groups, the picophytoplankton population (cyanobacteria, mostly Synechococcus) increased throughout the experiment and was more abundant in the warmer treatment though to a lesser extent when combined to high pCO2 level. These results suggest that under nutrient-depleted conditions in the Mediterranean Sea, ocean acidification has a very limited impact on the plankton community and that small species will benefit from warming with a potential decrease of the export and energy transfer to higher trophic levels.