Biodiversity and community assemblage of shallow habitats of the National Park of Banc d´Arguin (Mauritania): influence of habitat, season and site

O Banc d'Arguin, localizado ao longo da costa da Mauritânia, é uma zona húmida costeira de mais de 10.000 km2 com águas rasas, grandes leitos de ervas marinhas e planície de maré. Esta região que hospeda uma das maiores MPA da África, chamada Parc National du Banc d'Arguin, é um dos ecossistemas mais abundantes e diversificados do mundo, sustentando uma alta produção primária. Uma forte ressurgência de água rica em nutrientes no norte causa elevada produção primária de fitoplâncton nas áreas do norte do Banc. Na parte sul e sudeste, grandes planícies de marés e tapetes de ervas marinhas criam um ecossistema distinto associado a produção primária bentónica subtidal e intertidal. O Banc d'Arguin, é conhecido por hospedar um grande e diversificado painel de espécies, raras e ameaçadas de extinção de grande importância ecológica. O clima e os fatores abióticos encontrados nesta região, são únicos, com a presença de espécies temperadas, subtropicais e tropicais encontradas dentro de um mesmo ecossistema. Uma grande biodiversidade de espécies bentónicas, peixes, camarões, elasmobrânquios e pássaros são conhecidos por estar presentes nesta área onde a atividade pesqueira é estritamente controlada. Nesta área protegida estão autorizados apenas os Imraguens, pescadores locais espalhados por aldeias por todo o litoral, utilizando técnicas milenares para pescar dentro do PNBA. A presença de peixes de valor económico é conhecida e bem documentada na região. No entanto, a diversidade e composição do habitat costeiro de águas rasas, composto por grandes tapetes de ervas marinhas e bancos de areia, onde a maioria desses peixes e outras espécies amadurecem e recrutam, permanece parcialmente desconhecida. Esses habitats representam um fator chave para entender a grande biodiversidade encontrada no Banc d'Arguin. É importante ter um melhor entendimento da importância desses habitats e as consequências das possíveis mudanças que podem ocorrer. A biodiversidade de habitats de ervas marinhas e habitats de areia localizados em habitats de águas rasas do Banc d'Arguin foram amostradas com uma rede de arrasto em 3 locais, durante duas missões de amostragem em dezembro e abril. A rede permitiu-nos recolher amostras das áreas rasas intertidais e subtidais nos primeiros metros de água onde se encontram os tapetes de ervas marinhas. Os 3 locais de amostragem foram determinados com um habitat de ervas marinhas e um habitat de areia, amostrados dentro da mesma área geográfica. O local A presente no sul do Banc d'Arguin em Mamghar era uma baía costeira. O site B ficava em Iwik, na parte sudeste do Banc e era um local costeiro exposto. O local C ficava nas ilhas de Kiji e Nair, localizadas nas lagoas rasas a oeste de Iwik. Os 3 locais diferentes foram amostrados durante o inverno e a primavera para comparar os resultados entre as estações. Alguns locais de amostragem extras foram adicionados durante a amostragem da primavera, mas não usados na análise estatística. Essas amostragens extras em tapetes de ervas marinhas foram realizadas a fim de avaliar com mais precisão a composição de espécies desses habitats. Os objetivos deste estudo foram testar se a comunidade era diferentes entre os habitats, em termos de abundância, diversidade de espécies e estrutura, e o efeito da estação e do local. A comunidade era muito diferente entre os habitats em termos de abundância, diversidade de espécies e estrutura da comunidade. Os habitats de ervas marinhas compostos por Zostera noltei, Cymodocea nodosa e Halodule wrightii suportaram um maior número de indivíduos, espécies e diversidade do que a areia nua. Ambos os habitats foram dominados em abundância por Atherina boyeri e outras espécies encontradas em todos os habitats. No entanto, as espécies de ervas marinhas e areia associadas eram muito diferentes e explicavam as diferenças na estrutura da assembleia. Na verdade, o grande campo de ervas marinhas oferece um abrigo para muitas espécies, explicando a maior diversidade encontrada nesses habitats. A família e as espécies associadas às ervas marinhas eram espécies de: camarões; Stephanolepsis hispidus; Nicholsina usta; Fistularia tabacaria; Sepiidae; Sparidae; Tetraodontidae; Syngnathidae; Labridae; Lutjanidae e Serranidae. No entanto, as espécies de areia eram muito diferentes, com uma composição principalmente de espécies de peixes planos, como Citharichthys stampflii; Pegusa lascaris; Pegusa triophthalma; Psettodes belcheri; Solea senegalensis; Synaptura lusitanica, bem como várias espécies de raia, como Dasyatis margarita, Glaucostegus cemiculus ou Rhinobatos rhinobatos. O fator sazonalidade apenas apresentou diferenças no número de espécies, diversidade e estrutura da comunidade de peixes. A temporada de primavera suportou um maior número de espécies, supostamente correlacionado com o aparecimento de juvenis de um grande número de espécies, chegando a habitats protegidos rasos para se desenvolverem e partirem na temporada para águas mais profundas. No inverno algumas espécies estiveram presentes, como Eucinostomus melanopterus e não foram encontradas na primavera, ao contrário de Atherina boyeri e um maior número de outras espécies encontradas principalmente na primavera. Uma estratégia ecológica diferente explica as diferenças, no entanto, o maior número de espécies que aparecem na primavera é explicado por padrões sazonais, principalmente devido a diferenças nos fatores abióticos que ocorrem entre as estações. O fator local mostrou diferenças em termos de abundância e diversidade de espécies, entre Mamghar e os outros locais, mas não para a estrutura da comunidade. Supõe-se que a maior abundância e diversidade de espécies em Mamghar é devido a uma área mais protegida de fortes fatores abióticos, bem como uma disponibilidade de presas pode ser maior na zona. A quase totalidade dos indivíduos capturados eram jovens (98,7%), confirmando a função de berçário desses habitats rasos do Banc d'Arguin, especialmente no habitat de ervas marinhas onde a comunidade mais abundante e diversa é encontrada. Esta observação enfatizou a importância crucial dessas zonas para sustentar uma biodiversidade saudável e diversa em toda a região. No entanto, os estudos mais recentes mostram que essas áreas de berçário do Banc d’Arguin estão em perigo, com uma redução progressiva e, eventualmente, o desaparecimento dos grandes tapetes de ervas marinhas e planícies de maré devido ao aquecimento global e elevação do nível do mar. Potenciais eventos abióticos extremos com mais frequência, bem como as mudanças gerais que ocorrerão nestas décadas, podem alterar profundamente a comunidade nos habitats do Banc d'Arguin e afetar os padrões de sazonalidade atualmente observados.The biodiversity and community assemblages of seagrass and sand habitats located in shallow water habitats of the Banc d’Arguin were sampled with a beach seine at 3 sites, during two sampling missions in December and April. The objectives were to test if the community assemblages in term of abundance, species diversity and assemblage structure were different between habitats, as well as the effect of the season and the site. The community assemblage was found to be very different between habitats in term of abundance, species diversity and community assemblage structure. Seagrass habitats composed of Zostera noltei, Cymodocea nodosa and Halodule wrightii supported a larger number of individuals, species and diversity than bare sand. Both habitats were dominated in abundance by Atherina boyeri and other species found in all habitats. However, the seagrass and sand associated species, were very different and accounted for the differences in the assemblage structure. The large canopy of seagrass offers a shelter for a lot of species explaining the higher diversity found in these habitats. The season factor only showed differences in the number of species, diversity and fish assemblage structure. The spring season supported a larger number of species, supposedly correlated to the appearance of juveniles of a large number of species coming to nurseries in shallow protected habitat before leaving later in the season to deeper waters. The site factor showed differences in terms of abundance and species diversity only between Mamghar and the other sites, but not for the community assemblage structure. Almost all individuals caught were young juveniles (98.7%). It confirms the nursery function of the shallow habitats of the Banc d’Arguin, specially in seagrass habitat where the most abundant and diverse community is found. This work confirm that these large seagrass beds are essential in the development of the high biodiversity known to be found in the Banc d’Arguin

Le journal intime de Mireille Havet : entre écriture de soi et grand œuvre

Mireille Havet, born in 1898, meets early success through her poems. Being close to Apollinaire and Cocteau, she makes a name for herself in the literary sphere of the time. Simultaneously with her poems and her novel published in 1923, she writes a diary, started when she was still a teenager. Driven by this success, the young woman is gradually caught up by her two great passions: women and drugs. It results in a turbulence against which she will struggle to attempt to produce the great work she dreamed of. Over the years, she finally resigned and will focus on her diary. It became the only reconcilable medium with her lifestyle, her melancholy and extremely increasing drug addiction. She then tries to transcribe her soul into her diary, "to say and reveal [her] world" inside. This project, even if it is not the ideal fantasized work, yet contains all the poetry of Mireille Havet, and forms, after rereading, a "complete whole" almost unknown to the author herself. Can this journal then replace the failed masterpiece the diarist always dreamed of?Mireille Havet, née en 1898, rencontre très tôt le succès grâce à ses poèmes. Proche d’Apollinaire et de Cocteau, elle se fait une place dans le milieu littéraire de l’époque. Parallèlement à ses poèmes, et à son roman publié en 1923, elle écrit un journal intime, qu’elle commence alors qu’elle est encore adolescente. Forte de ses succès de jeunesse, la jeune femme se laisse alors peu à peu rattraper par la vie : les femmes et les drogues, ses deux grandes passions, l’entraînent dans un tourbillon dont elle peine à s’extraire pour produire la grande œuvre dont elle rêve. Résignée, au fil des années, elle se concentrera sur la rédaction de son journal, devenu le seul support s’accordant avec son mode de vie, sa mélancolie et son addiction de plus en plus extrême aux drogues. Elle tente alors de transcrire son âme dans ses carnets intimes, de « dire et révéler [son] monde » intérieur. Ce projet, s’il n’est pas celui, idéal, de l’œuvre fantasmée, contient cependant toute la poésie de Mireille Havet et s’avère, après relecture, former un « tout complet », presque à l’insu de son auteur. Ce journal peut-il alors remplacer la grande œuvre avortée dont la diariste a toujours rêvé

Investigating the influence of (Deoxy)fluorination on the lipophilicity of non-UV-active fluorinated alkanols and carbohydrates by a new log P determination method

Property tuning by fluorination is very effective for a number of purposes, and currently increasingly investigated for aliphatic compounds. An important application is lipophilicity (log?P) modulation. However, the determination of log?P is cumbersome for non-UV-active compounds. A new variation of the shake-flask log?P determination method is presented, enabling the measurement of log?P for fluorinated compounds with or without UV activity regardless of whether they are hydrophilic or lipophilic. No calibration curves or measurements of compound masses/aliquot volumes are required. With this method, the influence of fluorination on the lipophilicity of fluorinated aliphatic alcohols was determined, and the log?P values of fluorinated carbohydrates were measured. Interesting trends and changes, for example, for the dependence on relative stereochemistry, are reporte

Fast and optimal broad-band Stokes/Mueller polarimeter design by the use of a genetic algorithm

A fast multichannel Stokes/Mueller polarimeter with no mechanically moving parts has been designed to have close to optimal performance from 430-2000 nm by applying a genetic algorithm. Stokes (Mueller) polarimeters are characterized by their ability to analyze the full Stokes (Mueller) vector (matrix) of the incident light. This ability is characterized by the condition number, $\kappa$, which directly influences the measurement noise in polarimetric measurements. Due to the spectral dependence of the retardance in birefringent materials, it is not trivial to design a polarimeter using dispersive components. We present here both a method to do this optimization using a genetic algorithm, as well as simulation results. Our results include fast, broad-band polarimeter designs for spectrographic use, based on 2 and 3 Ferroelectric Liquid Crystals, whose material properties are taken from measured values. The results promise to reduce the measurement noise significantly over previous designs, up to a factor of 4.5 for a Mueller polarimeter, in addition to extending the spectral range.Comment: 10 pages, 6 figures, submitted to Optics Expres

2,6-Dide­oxy-2,6-imino-l-glycero-d-ido-heptitol

The title mol­ecule, C7H15NO5, the major product from selective enzymatic oxidation followed by hydrogeno­lysis of the corresponding azido­heptitol, was found by X-ray crystallography to exisit in a chair conformation with three axial hydroxyl groups. One of the hydroxymethyl groups is disordered over two sets of sites in a 0.590 (3):0.410 (3) ratio. In the crystal, O—H⋯O, O—H⋯(O,O), O—H⋯N and N—H⋯O hydrogen bonding occurs

Understanding multivalent effects in glycosidase inhibition using C-glycoside click clusters as molecular probes

The synthesis of the first examples of multivalent C-glycosides based on C60-fullerene or β-cyclodextrin cores by way of Cu(I)-catalyzed azide–alkyne cycloadditions is reported. These compounds were designed as molecular probes to understand the mechanisms underlying the outstanding multivalent effects observed in glycosidase inhibition. The inhibition results obtained support a multivalent-binding model based on two scenarios both involving nonspecific interactions and varying by the presence or the absence of active site specific interactions. The magnitude of the multivalent effect obtained depends on the identity of the glycosidase involved and more specifically on the accessibility of its catalytic active site. Large inhibitory multivalent effects can be obtained when both glycosidase active sites and non-catalytic sites at the protein surface are involved in binding events. On the other hand, nonspecific interactions alone are not sufficient to achieve relative affinity enhancements exceeding a simple statistical effect (i.e., a relative inhibition potency not better than one on a valence-corrected basis).Ministerio de Economía y Competitividad de España (MINECO) y Fondos Europeos de Desarrollo Regional (FEDER y FSE). SAF2013-44021-

Tryptophan Fluorescence Quenching in β-Lactam-Interacting Proteins Is Modulated by the Structure of Intermediates and Final Products of the Acylation Reaction

In most bacteria, β-lactam antibiotics inhibit the last cross-linking step of peptidoglycan synthesis by acylation of the active-site Ser of d,d-transpeptidases belonging to the penicillin-binding protein (PBP) family. In mycobacteria, cross-linking is mainly ensured by l,d-transpeptidases (LDTs), which are promising targets for the development of β-lactam-based therapies for multidrug-resistant tuberculosis. For this purpose, fluorescence spectroscopy is used to investigate the efficacy of LDT inactivation by β-lactams but the basis for fluorescence quenching during enzyme acylation remains unknown. In contrast to what has been reported for PBPs, we show here using a model l,d-transpeptidase (Ldt) that fluorescence quenching of Trp residues does not depend upon direct hydrophobic interaction between Trp residues and β-lactams. Rather, Trp fluorescence was quenched by the drug covalently bound to the active-site Cys residue of Ldt. Fluorescence quenching was not quantitatively determined by the size of the drug and was not specific of the thioester link connecting the β-lactam carbonyl to the catalytic Cys as quenching was also observed for acylation of the active-site Ser of β-lactamase BlaC from M. tuberculosis. Fluorescence quenching was extensive for reaction intermediates containing an amine anion and for acylenzymes containing an imine stabilized by mesomeric effect, but not for acylenzymes containing a protonated β-lactam nitrogen. Together, these results indicate that the extent of fluorescence quenching is determined by the status of the β-lactam nitrogen. Thus, fluorescence kinetics can provide information not only on the efficacy of enzyme inactivation but also on the structure of the covalent adducts responsible for enzyme inactivation

Chem. Sci.

The isobutyl side chain is a highly prevalent hydrophobic group in drugs, and it notably constitutes the side chain of leucine. Its replacement by a hexafluorinated version containing two CF3 groups may endow the target compound with new and advantageous properties, yet this modification remains overlooked due to the absence of a general and practical synthetic methodology. Herein, we report the first general method to introduce the hexafluoroisobutyl group into ketoesters, malonates, 1,3-diketones, Schiff base esters and malononitrile. We demonstrated that the reaction occurs through an elimination/allylic shift/hydrofluorination cascade process which efficiently overcomes the usual fluoride β-elimination observed with α-CF3-vinyl groups. We showed that with alkali metal bases, a pentafluorinated alkene is obtained predominantly, whereas the use of tetrabutylammonium fluoride (TBAF) allows hydrofluorination to occur. This tandem process represents a conceptually new pathway to synthesize bis-trifluoromethylated compounds. This methodology was applied to the multigram-scale synthesis of enantiopure (S)-5,5,5,5′,5′,5′-hexafluoroleucine.Interactions supramoléculaires sélectives et directionnelles à base de synthons fluorés hautement polaire