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Stipitate kelp species such as Laminaria digitata dominate most cold-water subtidal rocky shores and form underwater forests which are among the most productive coastal systems worldwide. Laminaria also sustains rich bacterial communities which offer a variety of biotechnological applications. However, to date, in-depth studies on the diversity and uniqueness of bacterial communities associated with this macroalgal species, their ecological role and their interactions with the alga are under-represented. To address this, the epibacterial populations associated with different thallus regions (holdfast, stipe, meristem, blade) of this brown seaweed were investigated using high-throughput Illumina sequencing of the 16S rRNA genes. The results show that epibacterial communities of the brown seaweed are significantly different and specific to the thallus region, with the shared bacterial population comprising of only 1.1% of the total amplicon sequence variants. The diverse holdfast and blade tissues formed distinct clusters while the meristem and stipe regions are more closely related. The data obtained further supports the hypothesis that macroalgal bacterial communities are shaped by morphological niches and display specificity.

International audience

International audience

International audience; Batroun coastal marine zone - North Lebanon - is subjected to the discharges of two terrestrial sources of contamination, the phosphate plant of Selaata and Al-Jaouz River. In the aim to study their impact on the horizontal variability of sea water characteristics at short spatio-temporal scale, the displacement of water masses was followed under different wind conditions through the movement of a free drifting drogue. The wind regime played an essential role in the displacement and spreading of various contaminants over a wide area. The impact of Selaata chemical plant was shown not to be limited to Batroun marine area but its impact may invade further neighbouring northern marine area of the Lebanese coast.

11 p.; This study aims to analyse the surface sediment of Batroun coastal area in North Lebanon in order to reveal the integrating impact of Selaata chemical plant on its biological properties. Sediment samples were collected with cores by diving at 12 stations in summer period between mid July and beginning of August 2003. The values of the hydobiological parameters in the first 3 cm were ranging respectively between: 4.17 to 7.9 for pH, 0 to 171 mV for Eh,, 0 to 0.94 µg.g-1 for chlorophyll a and 24 to 4166 ind.10 cm-2 for meiofauna. The results showed that there was a reverse relationship between chlorophyll a and meiofauna and that Batroun marine area could be separated in two main areas of influence The first area includes the stations located in front of the main north-western emissary and where the sediments were more acid and less oxygenated with strong odour of hydrogen sulphide accompanied with high chlorophyll a contents and low numbers of meiofauna. The second area is consisted of stations located to the south or far offshore from the plant and where the sediments are characterized by lower acidity and higher redox potential with low chlorophyll a concentrations and higher population of meifauna. Exception could be found in some stations like M8 and M 13 that presented particular cases. The impact on the biological indices was limited to plant proximity where conditions were more perturbing and the variability in the concentrations of chlorophyll a and the numbers of meiofauna were not depending on sediments compositions but on the nature and toxicity of particulate matters rejected out of plant's emissaries such as the phosphogypsum.

International audience; The sediments of twelve coastal stations located in Batroun marine area (North Lebanon, Levantine basin) which is subjected to the impact of Selaata phosphate fertilizers plant were studied horizontally and vertically during summer of 2003. In order to delimit the factory's spatial influence, the distribution of inorganic phosphate in surface sediments was explored and compared with orthophosphate mean concentrations in surface water. Also in order to draw a chronological history for the plant's functioning, the vertical distribution of inorganic phosphate associated with organic compounds (carbohydrates, proteins and lipids) distribution in the different levels of sediment down to 15 cm was studied. The concentrations of inorganic phosphate varied from 597 to 2279 ug.g-1 in the surface sediments of the stations located out of the main outlets' influence (M1 to M6 and M12 to M13), while they were extremely high, fluctuating between 8068 and 64256 ug.g-1 at the stations (M7 to M10) located under the direct influence of Selaata factory. A significant positive correlation existed between the inorganic phosphate in sediments and the orthophosphate in sea water. The wole studied area was affected by phosphate emissions and was classified into 2 zones: the first one is indirectly touched by the plant's effluents and located to the south and offshore of the factory, and the second directly influenced by the plant's outputs and located to the west and west-northern side. The penetration in different sediment levels showed that at stations located far from the plant's main outlets, there were difficulties in determining any of plant's history because of the homogeneity of phosphate and organic matter distribution associated to strong hydrodynamism. Where as the sediments of stations located in front of the west-northern outlets could elaborate and highlight part of the phosphate factory's operational history and could show that in this zone of Batroun marine area the plant's sedimentation rate had overcome that of the natural processes.

Vermetid reefs are a key intertidal habitat in the warm-temperate part of the Mediterranean Sea and in some subtropical and tropical regions in the Atlantic and Pacific oceans. This unique and highly diverse ecosystems is under siege due to both the high anthropogenic pressure and the global climate change, with documented local population declines in the Eastern Mediterranean. This study aims at evaluating the conservation state of vermetid reefs along the Lebanese coast (Eastern Mediterranean), where seawater warming, habitat degradation and coastal urbanization likely threaten their presence. In order to assess the conservation status of vermetid reefs in Lebanon, five sites were randomly selected among those belonging to three impact classes: i) not impacted (i.e. protected), ii) moderately impacted, and iii) impacted. Two different non-destructive methods were applied to assess the presence of living vermetids Dendropoma anguliferum (Monterosato, 1878) and Vermetus triquetrus (Bivona-Bernardi, 1832) which shape the reef, and the associated communities. Our results highlight that no living vermetid reefs were recorded in the impacted sites where evident signs of bio-physical erosion of the reef are already underway. Living individuals of Vermetus triquetrus were found in some not impacted and moderately impacted sites, while living individuals of the endemic reef-builder Dendropoma anguliferum were found only at very low densities at the not impacted (protected) site. Such findings corroborate preliminary observations of population decline in the Eastern Mediterranean, and of vermetid reefs vulnerability to human disturbances. This raises concerns about the near future persistence of vermetid reefs in the region, and represents a call for management and conservation actions to preserve this reef-building species in the Mediterranean Sea.

The new benthic toxic dinoflagellate Ostreopsis fattorussoi sp. nov. is described from eastern Mediterranean Sea Lebanon and Cyprus coasts, supported by morphological and molecular data. The plate formula, Po, 3’, 7’’, 6c, 7s, 5’’’, 2’’’’, is typical for the Ostreopsis genus. It differs from all other Ostreopsis species in that i) the curved suture between plates 1’ and 3’ makes them approximately hexagonal, ii) the 1’ plate lies in the left-half of the epitheca and is obliquely orientated leading to a characteristic shape of plate 6’’. The round thecal pores are bigger than the other two Mediterranean species (O. cf. ovata and O. cf. siamensis). O. fattorussoi is among the smallest species of the genus (DV: 60.07±5.63 μm, AP: 25.66±2.97 μm, W: 39.81±5.05 μm) along with O. ovata. Phylogenetic analyses based on the LSU and ITS rDNA shows that O. fattorussoi belongs to the Atlantic/Mediterranean Ostreopsis spp. clade separated from the other Ostreopsis species. O. fattorussoi produces OVTX-a and structural isomers OVTX-d and –e, O. cf. ovata is the only other species of this genus known to produce these toxins. The Lebanese O. fattorussoi did not produce the new palytoxin-like compounds (ovatoxin-i, ovatoxin-j1, ovatoxin-j2, and ovatoxin-k) that were previously found in O. fattorussoi from Cyprus. The toxin content was in the range of 0.28-0.94 pg. cell−1. In Lebanon coast, O. fattorussoi was recorded throughout the year 2015 (temperature range 18-31.5 °C), with peaks in June and August. This article is protected by copyright. All rights reserved.