Las especies invasoras en el Mediterráneo. ¿Hay que asustarse?

Vienen del Norte, vienen del Sur, vienen del océano Pacífico y del Caribe: se trata de especies exóticas que se adentran al Mediterráneo. Si consiguen reproducirse sin la ayuda del Hombre en su nueva área geográfica, esas especies son tachadas de "especies introducidas". Si logran un gran éxito, se dice que son "invasoras". Desde inicios del siglo XX, su número se ha duplicado cada 20 años. Ultimamente, su número se ha disparado, y el Mediterráneo se ha convertido en el mar más castigado del mundo por las especies introducidas. ¿Por qué? Cómo consiguen a cruzar océanos y continentes? ¿Como consiguen a sobrevivir y a tener éxito? ¿Tienen las especies introducidas un impacto ecológico positivo, neutral o negativo? Todas? ¿O sólo unas? En cuanto se refiere a la economía, ¿son beneficiosas o perjudiciales? En este segundo caso, ¿quiere decir que cada ciudadano está pagando cada año por las consecuencias económicas de las especies introducidas, y estará pagando indefinidamente? Entonces, ¿cómo se puede explicar que la gente ya no haya caído en la cuenta? ¿Que se puede hacer? ¿Nada? ¿Es un tributo imprescindible de la civilización globalizada? ¿O un disparatado dispalfarro? ¿Cómo es la legislación de los países ribereños del Mediterráneo, en cuanto a las especies introducidas? ¿Y en otras partes del mundo (Reino Unido, EEUU, Canadá, Australia, Nueva Zelanda, etc.), ¿Han encontrado la solución? Ahora bien ¿A donde vamos?Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Carte des peuplements benthiques en Méditerranée : constitution d'une banque de données géocodées et synthèse cartographique

International audienceCet article relate la création d'une banque de données géocodées pour l'étude des peuplements benthiques de Méditerranée occidentale. Une méthode de synthèse cartographique est présentée et discutée. Les cartes relatives aux peuplements benthiques existant sur une zone de 18 km N-S par 41 km E-W, comprise entre Toulon et La Ciotat ont été rassemblées. La finalité de celles-ci étant diverse, elles présentent un grand nombre de codes décrivant les peuplements benthiques qu'il a été nécessaire de standardiser afin d'homogénéser la base de données. Ensuite, ces cartes ont été numérisées, puis rectifiées géométriquement par rapport à une même projection. Après la standardisation du traît de côte, la banque de données a été créée avec un élément d'information (pixel) de 25 x 25 m. Elle se compose de sept secteurs se recouvrant partiellement et décrivant la zone totale étudiée. Ce découpage permet d'optimiser l'utilisation de la banque et la visualisation de la zone d'étude. Ensuite les différents secteurs ont été enregistrés sur un disque optique numérique relié à un micro-ordinateur. Au sein de chaque secteur, chaque point est pondéré par un facteur dépendant essentiellement des techniques d'observation ou de cartographie bionomiques des peuplements (observation de photographies aériennes, observation directe lors de plongées en sous-marin d'exploration, résultats bionomiques d'après prélèvements par dragages) et de l'année au cours de laquelle les relevés ou prélèvements ont été réalisés. La carte de synthèse est composée des points de pondération maximale trouvés sur l'ensemble des cartes, tandis que la différence en chaque point entre le code de pondération maximale et le code de pondération immédiatement inférieure, est reportée sur la carte des “désaccords”. Les résultats de ces traitements sont présentés. Une évolution de cette méthode de synthèse est discutée

Competition between the invasive macrophyte Caulerpa taxifolia and the seagrass Posidonia oceanica: contrasting strategies

<p>Abstract</p> <p>Background</p> <p>Plant defense strategy is usually a result of trade-offs between growth and differentiation (i.e. Optimal Defense Theory – ODT, Growth Differentiation Balance hypothesis – GDB, Plant Apparency Theory – PAT). Interaction between the introduced green alga <it>Caulerpa taxifolia </it>and the endemic seagrass <it>Posidonia oceanica </it>in the Mediterranean Sea offers the opportunity to investigate the plausibility of these theories. We have accordingly investigated defense metabolite content and growth year-round, on the basis of an interaction gradient.</p> <p>Results</p> <p>When in competition with <it>P. oceanica, C. taxifolia </it>exhibits increased frond length and decreased Caulerpenyne – CYN content (major terpene compound). In contrast, the length of <it>P. oceanica </it>leaves decreases when in competition with <it>C. taxifolia</it>. However, the turnover is faster, resulting in a reduction of leaf longevity and an increase on the number of leaves produced per year. The primary production is therefore enhanced by the presence of <it>C. taxifolia</it>. While the overall concentration of phenolic compounds does not decline, there is an increase in some phenolic compounds (including ferulic acid and a methyl 12-acetoxyricinoleate) and the density of tannin cells.</p> <p>Conclusion</p> <p>Interference between these two species determines the reaction of both, confirming that they compete for space and/or resources. <it>C. taxifolia </it>invests in growth rather than in chemical defense, more or less matching the assumptions of the ODT and/or PAT theories. In contrast, <it>P. oceanica </it>apparently invests in defense rather than growth, as predicted by the GDB hypothesis. However, on the basis of closer scrutiny of our results, the possibility that <it>P. oceanica </it>is successful in finding a compromise between more growth and more defense cannot be ruled out.</p

Trophic Requirements of the Sea Urchin Paracentrotus lividus Varies at Different Life Stages: Comprehension of Species Ecology and Implications for Effective Feeding Formulations

Investigations on trophic requirements of different life cycle stages of Paracentrotus lividus are crucial for the comprehension of species ecology and for its artificial rearing. The future success of echinoculture depends heavily on the development of suitable and cost-effective diets that are specifically designed to maximize somatic growth during the early life stages and gonadal production in the later stages. In this context, a considerable number of studies have recommended animal sources as supplements in sea urchin diets. However, with the exception of Fernandez and Boudouresque (2000), no studies have investigated the dietary requirements over the different life stages of the sea urchin. In the present study, the growth and nutrition of three life stages of P. lividus (juveniles: 15-25 mm; subadults: 25-35 mm; adults: 45-55 mm) were analyzed over a 4-month rearing experiment. Three experimental diets, with 0%, 20% and 40% of animal sourced enrichments, were tested in parallel in sea urchin three size classes. The food conversion ratio, somatic and gonadal growth were assessed in each condition in order to evaluate the optimal level of animal-sourced supplements for each life stage. A general growth model covering the full post-metamorphic P. lividus life cycle was defined for each condition. During the juvenile stage P. lividus requires higher animal supply (40%), while a feeding requirement shift takes place toward lower animal supply (20%) in sub-adult and adult stages. Our results evidenced that the progressive increase in size after the metamorphosis led to a consequent variation of trophic requirements and food energy allocation in the sea urchin P. lividus. Macronutrient requirements varied widely during the different life stages, in response to changes in the energy allocation from somatic growth to reproductive investment. This study sheds light on P. lividus trophic ecology, broadening our basic knowledge of the dietary requirements of juveniles, sub-adults and adults as a function of their behavior also in the natural environment

Ecosystem-based assessment of a widespread Mediterranean marine habitat: The Coastal Detrital Bottoms, with a special focus on epibenthic assemblages

IntroductionCoastal detrital bottoms (CDB) are one of the most extensive habitats of the continental shelf worldwide, in the upper levels of the circalittoral zone. Hosting a diverse community structured by sediment grain size, trophic interactions and calcified organisms, CDB exhibit important ecological functions. In the Mediterranean Sea, CDB are constituted by recent elements partly provided by adjacent infralittoral and circalittoral ecosystems. Since the 2010s, the offshore extension of many Marine Protected Areas (MPAs) has resulted in the incorporation of vast areas of CDB, raising the issue of their management. The Marine Strategy Framework Directive (MSFD) has embraced the concept of an ecosystem-based approach involving taking into account the functioning of marine habitats and their related ecosystem services. The purpose of this paper is to propose an ecosystem-based quality index (EBQI) tested on CDB from the north-western Mediterranean Sea, focusing mainly on epibenthic assemblages.MethodsThe first step has been to define a conceptual model of the CDB functioning, including the main trophic compartments and their relative weighting, then to identify appropriate assessment methods and potential descriptors. Twenty-nine sites were sampled along the coast of Provence and French Riviera (Southern France). Study sites were chosen with a view to encompassing a wide range of hydrological conditions and human pressures.ResultsVery well-preserved sites were found in Provence in areas without trawling and terrigenous inputs, while impacted and low-ES sites were located in the vicinity of urbanized areas. The cover of rhodoliths characterizes the seascape and might be an indicator of the good ES of CDB and reduced human pressure. However, the absence of rhodoliths may also be induced by natural phenomena.DiscussionThe EBQI designed for CDB proved representative and useful for a functional assessment based on epibenthic assemblages. However, some descriptors have shown their limitations and should be further explored. We highlight here the priority of establishing an index corresponding to a societal demand (e.g., European Directives, Barcelona convention) as a basis for a broad and large-scale assessment, for practical reasons. We stress the need to better apprehend the role of the macro-infauna and to extend this index over a wider geographical scale

Minouche Knoepffler-Péguy (1934-2018), the 'Dame de Banyuls' (the Lady of Banyuls)

International audienc

Taxonomie et phylogénie des Eucaryotes unicellulaires.

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Qu'est-ce qu'une lagune méditerranéenne ?

National audiencenot availabl