From In Situ to satellite observations of pelagic Sargassum distribution and aggregation in the Tropical North Atlantic Ocean

International audienceThe present study reports on observations carried out in the Tropical North Atlantic in summer and autumn 2017, documenting Sargassum aggregations using both ship-deck observations and satellite sensor observations at three resolutions (MSI-10 m, OLCI-300 m, VIIRS-750 m and MODIS-1 km). Both datasets reported that in summer, Sargassum aggre-gations were mainly observed off Brazil and near the Caribbean Islands, while they accumulated near the African coast in autumn. Based on in situ observations, we propose a five-class typology allowing standardisation of the description of in situ Sargassum raft shapes and sizes. The most commonly observed Sargassum raft type was windrows, but large rafts composed of a quasi-circular patch hundreds of meters wide were also observed. Satellite imagery showed that these rafts formed larger Sargassum aggregations over a wide range of scales, with smaller aggregations (of tens of m 2 area) nested within larger ones (of hundreds of km 2). Match-ups between different satellite sensors and in situ observations were limited for this dataset, mainly because of high cloud cover during the periods of observation. Nevertheless, comparisons between the two datasets showed that satellite sensors successfully detected Sargassum abundance and aggregation patterns consistent with in situ observations. MODIS and VIIRS sensors were better suited to describing the Sargas-sum aggregation distribution and dynamics at Atlantic scale, while the new sensors, OLCI and MSI, proved their ability to detect Sargassum aggregations and to describe their (sub-) mesoscale nested structure. The high variability in raft shape, size, thickness, depth and biomass density observed in situ means that caution is called for when using satellite maps of Sargassum distribution and biomass estimation. Improvements would require additional in situ and airborne observations or very high-resolution satellite imagery

Maximizing the Products Display for Purchaser Lucidity and Alleviation in Circulation to Augment the Sale of Supermarket: Milieu of Bangladesh

The purpose of this study is to appraise the accessible products display for the purchaser lucidity which may maximizes offers and actions of business with the alleviation in circulation to augment the random sale in the arena of supermarket. The study scrutinizes a fundamental research on the context of Bangladesh and especially for the Dhaka zone. A supermarket, a large form of the traditional grocery store, is a self-service shop offering a wide variety of food and household products, organized into aisles. It is larger in size and has a wider selection than a traditional grocery store, but is smaller and more limited in the range of merchandise than a hypermarket or big-box market. The traditional supermarket occupies a large amount of floor space, usually on a single level. It is usually situated near a residential area in order to be convenient to consumers. The basic appeal is the availability of a broad selection of goods under a single roof, at relatively low prices. Other advantages include ease of parking and frequently the convenience of shopping hours that extend far into the evening or even 24 hours a day. Key words: Circulation, Supermarket, Alleviation, Sale, Products, Variation, Lucidit

Future HAB science: Directions and challenges in a changing climate

There is increasing concern that accelerating environmental change attributed to human-induced warming of the planet may substantially alter the patterns, distribution and intensity of Harmful Algal Blooms (HABs). Changes in temperature, ocean acidification, precipitation, nutrient stress or availability, and the physical structure of the water column all influence the productivity, composition, and global range of phytoplankton assemblages, but large uncertainty remains about how integration of these climate drivers might shape future HABs. Presented here are the collective deliberations from a symposium on HABs and climate change where the research challenges to understanding potential linkages between HABs and climate were considered, along with new research directions to better define these linkages. In addition to the likely effects of physical (temperature, salinity, stratification, light, changing storm intensity), chemical (nutrients, ocean acidification), and biological (grazer) drivers on microalgae (senso lato), symposium participants explored more broadly the subjects of cyanobacterial HABs, benthic HABs, HAB effects on fisheries, HAB modelling challenges, and the contributions that molecular approaches can bring to HAB studies. There was consensus that alongside traditional research, HAB scientists must set new courses of research and practices to deliver the conceptual and quantitative advances required to forecast future HAB trends. These different practices encompass laboratory and field studies, long-term observational programs, retrospectives, as well as the study of socioeconomic drivers and linkages with aquaculture and fisheries. In anticipation of growing HAB problems, research on potential mitigation strategies should be a priority. It is recommended that a substantial portion of HAB research among laboratories be directed collectively at a small sub-set of HAB species and questions in order to fast-track advances in our understanding. Climate-driven changes in coastal oceanographic and ecological systems are becoming substantial, in some cases exacerbated by localized human activities. That, combined with the slow pace of decreasing global carbon emissions, signals the urgency for HAB scientists to accelerate efforts across disciplines to provide society with the necessary insights regarding future HAB trends

Coralline Algae in a Changing Mediterranean Sea: How Can We Predict Their Future, if We Do Not Know Their Present?

In this review we assess the state of knowledge for the coralline algae of the Mediterranean Sea, a group of calcareous seaweeds imperfectly known and considered highly vulnerable to long-term climate change. Corallines have occurred in the Mediterranean area for ∼140 My and are well-represented in the subsequent fossil record; for some species currently common the fossil documentation dates back to the Oligocene, with a major role in the sedimentary record of some areas. Some Mediterranean corallines are key ecosystem engineers that produce or consolidate biogenic habitats (e.g., coralligenous concretions, Lithophyllum byssoides rims, rims of articulated corallines, maerl/rhodolith beds). Although bioconstructions built by corallines exist virtually in every sea, in the Mediterranean they reach a particularly high spatial and bathymetric extent (coralligenous concretions alone are estimated to exceed 2,700 km2 in surface). Overall, composition, dynamics and responses to human disturbances of coralline-dominated communities have been well-studied; except for a few species, however, the biology of Mediterranean corallines is poorly known. In terms of diversity, 60 species of corallines are currently reported from the Mediterranean. This number, however, is based on morphological assessments and recent studies incorporating molecular data suggest that the correct estimate is probably much higher. The responses of Mediterranean corallines to climate change have been the subject of several recent studies that documented their tolerance/sensitivity to elevated temperatures and pCO2. These investigations have focused on a few species and should be extended to a wider taxonomic set

Mediterranean bioconstructions along the Italian coast

Marine bioconstructions are biodiversity-rich, three-dimensional biogenic structures, regulating key ecological functions of benthic ecosystems worldwide. Tropical coral reefs are outstanding for their beauty, diversity and complexity, but analogous types of bioconstructions are also present in temperate seas. The main bioconstructions in the Mediterranean Sea are represented by coralligenous formations, vermetid reefs, deep-sea cold-water corals, Lithophyllum byssoides trottoirs, coral banks formed by the shallow-water corals Cladocora caespitosa or Astroides calycularis, and sabellariid or serpulid worm reefs. Bioconstructions change the morphological and chemicophysical features of primary substrates and create new habitats for a large variety of organisms, playing pivotal roles in ecosystem functioning. In spite of their importance, Mediterranean bioconstructions have not received the same attention that tropical coral reefs have, and the knowledge of their biology, ecology and distribution is still fragmentary. All existing data about the spatial distribution of Italian bioconstructions have been collected, together with information about their growth patterns, dynamics and connectivity. The degradation of these habitats as a consequence of anthropogenic pressures (pollution, organic enrichment, fishery, coastal development, direct physical disturbance), climate change and the spread of invasive species was also investigated. The study of bioconstructions requires a holistic approach leading to a better understanding of their ecology and the application of more insightful management and conservation measures at basin scale, within ecologically coherent units based on connectivity: the cells of ecosystem functioning

L'activité respiratoire d'une bactérie marine, Marinobacter hydrocarbonoclasticus sp. 17, en fonction de la pression hydrostatique

National audienceL'activité respiratoire d'une bactérie marine, Marinobacter hydrocarbonoclasticus sp. 17, en fonction de la pression hydrostatiqu

Global change in the NW Mediterranean Sea : the fate of forests of Cystoseira and Sargassum, Lithophyllum rims and blooms of Ostreopsis

Dans la plupart des mers et des océans, la zone littorale est dominée par de grandes Phaeophyceae (Laminariales et Fucales) qui jouent un rôle écologique majeur dans la structuration et le fonctionnement de l’écosystème (fourniture d’habitats, de nourri ture, de frayères et de nurseries pour de nombreuses espèces). En Méditerranée, ce sont les espèces de Fucales appartenant aux genres Cystoseira C. Agardh et Sargassum C. Agardh qui sont les principales espèces structurantes du stade climacique de la végétation photophile de la zone littorale (de la surface jusqu’à 70-80 m de profondeur dans les eaux les plus claires). L’étude diachronique menée dans ce travail de thèse à partir des premières observations scientifiques exploitables (18ème siècle) est une première en Méditerranée sur autant de linéaire de côte (~ 2 970 km à l’échelle 2 500ème). Les résultats obtenus par l’analyse des données historiques et actuelles de distribution des Fucales le long des côtes françaises différent suivant les espèces étudiées, aussi bien en ce qui concerne l’état de conservation des populations que les causes impliquées dans leur régression. Dans l’ensemble, les forêts de Cystoseira et de Sargassum ont régressé de façon drastique en Méditerranée française. L’écosystème a souvent basculé (regime shift) vers un état stable alternatif (Multiple Stable State) de type barren ground, caractérisé par la dominance de macrophytes calcifiés encroûtants (corallinacées) et d’oursins.Throughout the world, coastal ecosystems are severely affected by the cumulative impact of increasing human pressure (e.g. destruction of habitats, pollution, non-indigenous species, overfishing, coastal aquaculture and global warming). Different foms of stress act over time and in unison, with a possible synergistic effect, on species, ecosystems and their ability to deliver ecosystem services. Along temperate rocky coasts worldwide, large canopy-forming kelps (Laminariales, Phaeophyceae, Ochrophyta) and fucoids (Fucales, Phaeophyceae, Ochrophyta) represent the dominant species in pristine environments. In the Mediterranean Sea, species of the genus Cystoseira C. Agardh and Sargassum C. Agardh are habitat-forming species dominating several assemblages from the littoral fringe down to the lower sublittoral zone (0 down to 70-80 m depth). The present diachronic study based on the first usable scientific observations (18th century) is the first in the Mediterranean to cover such a long stretch of coastline (~ 2970 km at 1/2 500 scale). The results obtained by the analysis of historical and current data on the distribution of Fucales along the French coast differ according to the species studied, both with regard to the conservation status of populations and the causes involved in their regression. The general loss of habitat-structuring species is worrying. We are witnessing a typical regime shift with a replacement of macroalgal forests by less structured algal assemblages dominated by Corallinales or by barren grounds dominated by encrusting species, filamentous algae and sea urchins

Le site WEB MediOs 2 : un outil d'échanges d'informations indispensable au bon fonctionnement du projet.

National audienceLe site WEB MediOs 2 : un outil d'échanges d'informations indispensable au bon fonctionnement du projet

Le dinoflagellé Ostreopsis : petite cause grandes conséquences. GisPosidonie : Plus de 30 ans au service de la protection et de la gestion du milieu marin. Le Diréach L. et Boudouresque C.F. eds., Gis Posidonie publ., Marseille : 151-154.

Livre des 30ans du GIS PosidoniesLe dinoflagellé Ostreopsis : petite cause grandes conséquences. GisPosidonie : Plus de 30 ans au service de la protection et de la gestion du milieu marin. Le Diréach L. et Boudouresque C.F. eds., Gis Posidonie publ., Marseille : 151-154

Projet OSCREEN. Dénombrements de dinoflagellés benthiques et identification de macrophytes. Contrat Ifremer - Gis Posidonie. 30p.

Rapport scientifiqueProjet OSCREEN. Dénombrements de dinoflagellés benthiques et identification de macrophytes