Quantification of environment-driven changes in epiphytic macroinvertebrate communities associated to Phragmites australis

The epiphytic macroinvertebrate communities associated with the Common Reed, Phragmites australis (Cav.) Trin. ex Steudel, were examined seasonally from summer 2004 to spring 2005 in eleven coastal lagoons of the Llobregat Delta (NE Spain) following the method proposed by Kornijów & Kairesalo (1994). The aims of the study were to: 1) characterise and quantify changes in epiphytic macroinvertebrate communities along environmental gradients; 2) assess the contribution of elements of the epiphytic compartment to structuring the community; 3) define the optima and tolerances of selected epiphytic macroinvertebrate taxa for the most relevant ecological factors responsible for assemblage composition; and 4) identify possible epiphytic species assemblages that would allow a lagoon"s typology to be established, as well as their representative indicator species. Communities showed statistically significant seasonal variation, with two faunal peaks: one in summer, with high chironomid densities, and the other in winter, with high naidid densities. These peaks showed a clear response to the influence of environmental factors. Salinity explained the highest percentage of total variance (36%), while trophic variables (nutrients, phytoplanktonic chlorophyll-a, and total organic carbon) and epiphyton biomass (19.2 and 4% of total variance explained, respectively) were secondary. Three different epiphytic macroinvertebrate species assemblages could be defined. These assemblages were directly linked to conductivity conditions, which determined the rate of survival of certain taxa, and to the existence of a direct connection with the sea, which permitted the establishment of 'brackish-water' species. In spite of the existence of these species assemblages, the species composition and biomass of epiphytic macroinvertebrates and epiphyton differed substantially between lagoons; both elements were subject to changes in the environment, which finally determined the site-to-site variation in the density and composition of the macroinvertebrate population

Contribucio al coneixement de les algues epifitiques en llacunes litorals

Es presenten els resultats sobre les algues epifítiques d'hidròfits i helòfits en llacunes litorals. En general, les poblacions d'algues son forca diversificades, destacant el grup de les diatomees, seguides de lluny per les clorofícies y les cianofícies. En general totes les plantes aquàtiques es troben forca epifitades. No obstant, les tiges de Phragmites australis presenten unes poblacions d'algues epifítiques molt importants, que es troben dominades per Cladophora glomerata v. crassior o Rhizoclonium riparium, acompanyades per un gran nombre d'espècies subordinades.

Macroinvertebrate assemblages on reed beds, with special attention to Chironomidae (Diptera), in Mediterranean shallow lakes.

Macroinvertebrates associated to reed-beds (Phragmites australis) in six shallow natural water bodies along the 220 km of coast of the Comunidad Valenciana (Spain) were studied. These sites were selected to reflect different trophic states, but also, and due to the natural variability of mediterranean wetlands, they greatly differ in salinity and hydroperiod. To unify the sampling, reed bed was chosen to provide data from a habitat common to all wetlands, including the most eutrophic ones where submerged macrophytes have disappeared due to water turbidity. Individual submerged stems of Phragmites australis were sampled along with the surrounding water. The animal density found refers to the available stem surface area for colonization. Forty-one taxa were recorded in total, finding Chironomidae to be the most important group, quantitatively and qualitatively. In freshwater sites it was observed an increase in macroinvertebrate"s density at higher trophic states. Nevertheless each studied region had a different fauna. The PCA analysis with macroinvertebrate groups distinguished three types of environment: freshwaters (characterized by swimming insect larvae, collectors and predators, oligochaetes and Orthocladiinae), saline waters (characterized by crustaceans and Chironominae) and the spring pool, which shares both taxa. Chironomids were paid special attention for being the most abundant. A DCA analysis based on the relative abundance of Chironomids reveals salinity as the main characteristic responsible for its distribution, but trophic state and hydrological regime were also shown to be important factors.

Ontogenetic dietary changes in male South American fur seals Arctocephalus australis in northern and central Patagonia, Argentina.

This study assessed ontogenetic dietary changes in male South American fur seals Arctocephalus australis in northern and central Patagonia (Argentina) using stable isotope ratios (δ15 N and δ13 C) in vibrissae and bones. Sucking pups were characterised by higher δ15 N values and lower δ13 C values than older specimens. Weaning was associated with a marked drop of δ15 N values, both in bone and vibrissae. Such a drop was inconsistent with the consumption of local prey and may reveal movement to distant foraging grounds or physiological changes associated with either fasting or rapid growth. Stable isotope ratios indicated that juveniles fed more pelagically than subadults and adults, but that there were no major differences between the 2 latter age categories. As subadults and adults are rather similar in body mass and are much larger than juveniles, body mass may play a role in the ontogenetic dietary changes reported. Nevertheless, demersal benthic prey were always scarce in the diet of male fur seals, which relied primarily on Argentine shortfin squid and small pelagic fish throughout life, though adults also consumed large amounts of decapod crustaceans available at shallow depths. Vibrissae did not reveal regular oscillations of δ15 N or δ13 C, except in 1 individual. Thus, male fur seals from northern and central Patagonia do not appear to migrate regularly between isotopically distinct areas, although nomadic displacements cannot be ruled out.

Joan Ramis i La nouvelle Héloïse de Rousseau : una lectura rousseauniana de l'obra dramàtica de Ramis

Aquest estudi es proposa estudiar els vincles que hi ha entre La nouvelle Héloïse (1761) de Jean-Jacques Rousseau i l'obra dramàtica de Joan Ramis i Ramis, especialment la seva Lucrècia (1769), tot i les dificultats que la recepció de Rousseau va tenir en la Menorca il·lustrada. En aquest sentit, el gruix del treball es dedica als elements que tenen en comú les obres de referència, pel que fa al tractament literari dels temes centrals, com ara el que vehicula la sensibilitat preromàntica que irromp en el panorama creatiu de l'Europa del moment, més enllà de les propostes estrictament formals i de contingut del neoclassicisme, i també quant als motius i la intencionalitat dels dos autors.

Efecte de la recurrència dels incendis sobre la vegetació i el sòl a les zones de matollar del Macizo Central Ourensano

El matollar sec europeu format per Erica australis, Erica arborea, Pterosparum tridentatum, Halimium lasianthum i Calluna vulgaris com a espècies predominants és cremat en les serralades del Massís Central de forma repetida durant el pas dels anys. Això ha sigut, tradicionalment, a causa de la necessitat de mantenir-lo transitable per al bestiar, encara que altres circumstàncies s’han afegit actualment a aquesta necessitat, que incrementen el risc d’incendi d’aquesta comunitat, disparant-se el número d’incendis en els últims 30 anys. Sabent això, vam decidir realitzar un estudi a les zones de matollar que trobem al Massís Central situat a la zona del Concello de Villariño de Conso, a Ourense, per conèixer com es comporten les espècies característiques d’aquest tipus d’ecosistema després dels incendis, mitjançant la realització de mostrejos i perfils del sòl. D’aquesta manera hem volgut veure com es desenvolupen les espècies vegetals de matollar al llarg del temps, després de ser cremats. Gràcies a l’estudi hem pogut veure com el matollar observat te unes característiques que li permet sobreviure als incendis i tindre una capacitat de regeneració elevada després de patir aquesta pertorbació. Això es degut a la capacitat per rebrotar d’aquestes espècies arbustives i a la seva competitivitat. També hem vist com a necessari, donar un valor econòmic a la bona conservació de l’hàbitat, per tal de que la població local abandoni pràctiques de gestió forestal nocives, com el foc.

Geografia i experiència professional: entrevista a deu joves geògrafs i geògrafes

En aquest article es presenta el relat de les històries personals de deu joves geògrafs i geògrafes centrades en la seva formació acadèmica i en les respectives experiències i trajectòries en el món laboral. No pretén ser una mostra representativa de l’actual panorama professional al nostre país, sinó, tan sols, fer arribar al lector deu trajectòries individuals que tenen com a fil conductor l’intent d’assolir l’exercici professional i estable de la geografia

Species identification of two sympatric hakes by allozymic markers

Samples were collected from hake species Merluccius australis and M. hubbsi in the south west Atlantic Ocean. Enzyme electrophoretic analysis of the eye, liver and muscle revealed 5 out of 33 genetic loci with species-specific allelic frequencies. These five loci provide a set of genetic markers for individual classification

Estudi per a la construcció de l'EDAR mitjançant filtres verds de la Nou de Gaià (Tarragonès)

El tractament de les aigües en nuclis menors de 2000 habitants es troba pendent de completar per part de l’Agència Catalana de l’Aigua més concretament al corresponent Pla de Sanejament d’Aigües Residuals Urbanes (PSARU). El nucli de La Nou de Gaià (al Tarragonès) es troba pendent de la construcció de la corresponent instal·lació de sanejament, projectada al 2007. Alternativament a les depuradores tradicionals basades en l’ús de formigó (o materials alternatius) i en la despesa elèctrica per assegurar una aeració i una evacuació dels fangs generats, existeixen tecnologies “toves”. Aquestes tecnologies, també conegudes com a “verdes”, es basen en imitar els sistemes naturals maximitzant el seu potencial d’autodepuració. A grans trets existeixen dos formes de depurar les aigües de forma ecològica”: llacunatges (existeix una capa d’aigua lliure) i filtres verds. El present estudi es basa en l’aplicació de filtres verds de morfologia vertical i flux subsuperficial, plantat amb canyes dels generes Scirpus o Phragmites. El resultat han estat 4 bases de 35*35 per a tractar un cabal de 150 m3/d i una població equivalent de 1272.

Genetic variation for carbon isotope composition in Juglans regia L.: relationships with growth, phenology and climate of origin

Among the traits of breeding interest for the common walnut tree Juglans regia L., characteristics such as timing of budbreak and leaf fall, water-use efficiency and growth performance are regarded as being of utmost relevance in Mediterranean conditions. The authors evaluated intraspecific variation in $\delta$13C (carbon isotope composition, surrogate of intrinsic water-use efficiency, WUE$_{\rm i}$) for 22 J. regia families grown in a progeny test under supplementary irrigation, and investigated whether such variation correlated with climatic indicators of native habitats. The genetic relationships between $\delta$13C, growth and phenology were also assessed during two consecutive years. Overall, the most water-use-efficient families (i.e. with higher $\delta$13C), which originated mainly from drought-prone provenance regions which have a high vapour pressure deficit and low rainfall, exhibited less height growth and smaller DBH. Using a stepwise regression procedure, $\delta$13C was included as the main explanatory variable of genotypic variation in growth traits, together with growing season duration (for DBH in both years) and flushing (for height in 2007). It was concluded that WUE$_{\rm i}$ is largely unconnected to phenology effects in the explanation of growth performance for J. regia, therefore suggesting the opportunity of simultaneously selecting for low WUE$_{\rm i}$ and extended growing period to maximise productivity in non-water-limited environments.

Barley Yellow Dwarf Virus (BYDV) y los áfidos en los arrozales levantinos: una prospección

Se ha llevado a cabo una prospección de las poblaciones emigrantes de áfidos alados en el área de La Albufera de Valencia, zona donde se da el «enrojat» del arroz, enfermedad causada por una raza del Barley Yellow Dwarf Virus, y se discute aquí el potencial presumible de las distintas especies como vectores de la enfermedad. Se muestrearon dos áreas con diferente incidencia de la enfermedad, obteniéndose 30 especies, de las que ocho están descritas como vectores de tales virus. Fueron mayores las capturas en las áreas donde se cultivaba el arroz por plantel y transplante con incidencia marcada de la enfermedad, que en otras de menor incidencia. La aparente homogeneidad de la zona hace difícil comprender la razón de tales diferencias. Entre los vectores conocidos de BYDV, sólo Rhopalosiphon padi L. y Hyaiopterus pruni (L) Geof. aparecieron al principio de la estación, cuando tiene lugar la infección, con poblaciones considerables. E1 primero es el vector conocido de la enfermedad. El segundo, es de las pocas especies que tiene niveles similares de captura en ambas áreas. Ninguno de los otros áfidos vectores capturados como alados parece verdaderamente importante para la transmisión a pleno campo por lo tardío de su llegada a los campos o por razones de su ciclo vital. Se ha intentado estudiar el potencial de Hyalopterus pruni, pulgón muy abundante en los carrizos como transmisor a corta distancia a partir de estas plantas. No se han obtenido resultados positivos ni a partir de la planta, ni a partir de áfidos alimentados en arroz o avena infectadas previamente con la enfermedad.

Stable isotopes indicate population structuring in the Southwest Atlantic population of right whales

From the early 17th century to the 1970s southern right whales, Eubalaena australis, were subject to intense exploitation along the Atlantic coast of South America. Catches along this coast recorded by whalers originally formed a continuum from Brazil to Tierra del Fuego. Nevertheless, the recovery of the population has apparently occurred fragmentarily, and with two main areas of concentration, one off southern Brazil (Santa Catarina) and another off central Argentina (Peninsula Valdés). This pattern suggests some level of heterogeneity amongst the population, which is apparently contradicted by records that traced individuals moving throughout the whole geographical extension covered by the species in the Southwest Atlantic. To test the hypothesis of the potential occurrence of discrete subpopulations exploiting specific habitats, we investigated N, C and O isotopic values in 125 bone samples obtained from whaling factories operating in the early 1970s in southern Brazil (n = 72) and from contemporary and more recent strandings occurring in central Argentina (n = 53). Results indicated significant differences between the two sampling areas, being δ13C and δ18O values significantly higher in samples from southern Brazil than in those from central Argentina. This variation was consistent with isotopic baselines from the two areas, indicating the occurrence of some level of structure in the Southwest Atlantic right whale population and equally that whales more likely feed in areas commonly thought to exclusively serve as nursing grounds. Results aim at reconsidering of the units currently used in the management of the southern right whale in the Southwest Atlantic Ocean. In the context of the current die-off affecting the species in Peninsula Valdés, these results also highlight the necessity to better understand movements of individuals and precisely identify their feeding areas.

Longer and less overlapping food webs in anthropogenically disturbed marine ecosystems: confirmations from the past

The human exploitation of marine resources is characterised by the preferential removal of the largest species. Although this is expected to modify the structure of food webs, we have a relatively poor understanding of the potential consequences of such alteration. Here, we take advantage of a collection of ancient consumer tissues, using stable isotope analysis and SIBER to assess changes in the structure of coastal marine food webs in the South-western Atlantic through the second half of the Holocene as a result of the sequential exploitation of marine resources by hunter-gatherers, western sealers and modern fishermen. Samples were collected from shell middens and museums. Shells of both modern and archaeological intertidal herbivorous molluscs were used to reconstruct changes in the stable isotopic baseline, while modern and archaeological bones of the South American sea lion Otaria flavescens, South American fur seal Arctocephalus australis and Magellanic penguin Spheniscus magellanicus were used to analyse changes in the structure of the community of top predators. We found that ancient food webs were shorter, more redundant and more overlapping than current ones, both in northern-central Patagonia and southern Patagonia. These surprising results may be best explained by the huge impact of western sealing on pinnipeds during the fur trade period, rather than the impact of fishing on fish populations. As a consequence, the populations of pinnipeds at the end of the sealing period were likely well below the ecosystem's carrying capacity, which resulted in a release of intraspecific competition and a shift towards larger and higher trophic level prey. This in turn led to longer and less overlapping food webs.

Patrimonio cultural y turismo: nuevos modelos de promoción vía Internet

Desde Estambul a Barcelona, de Almería a Niza, de Venecia a Túnez, de Atenas a Alejandría, de la India a la China, el mundo ofrece una actividad cultural rica y muy variada. Los turistas que lo recorren desean impregnarse de ella. Parece como si el sector turístico no haya sido capaz de organizarse y desarrollar un proyecto común de turismo cultural que hermane todas estas posibilidades. Quizá en un futuro, con el uso de las nuevas tecnologías se puedan proponer viajes virtuales por el patrimonio cultural del mediterráneo como preámbulo y estimulo de posibles viajes reales