165 research outputs found
L'impacte ambiental del Pla Hidrològic en el tram final de l'Ebre
En aquest article es presenta una sÃntesi de les alteracions que produeixen les detraccions d’aigua dels rius sobre el cicle de l’aigua i ecosistemes associats. En concret, s’analitzen els impactes ambientals que pot ocasionar el transvasament d’aigua de l’Ebre, previst en el Pla Hidrològic Nacional, sobre els hà bitats i biotes fluvials, la desembocadura. l’ecosistema marà i els usos actuals del medi. Aixà mateix, es valoren les alternatives i els estudis necessaris per a minimitzar l’ afecció.En este artÃculo se presenta una sÃntesis de las alteraciones que producen las detracciones de agua de los rÃos sobre el ciclo del agua y ecosistemas asociados. En concreto, se analizan los impactos ambientales que puede ocasionar el trasvase de agua de la cuenca del Ebro, previsto en el Plan Hidrológico Nacional, sobre los hábitats y biotas fluviales, la desembocadura, el ecosistema marino y los usos actuales del medio. Asimismo, se valoran las alternativas y los estudios necesarios para minimizar la afección.This article provides a synthesis of the modifications caused by river water extractions to the water cycle and associated ecosystems. Specifically, it analyses the potential environmental impacts of water transfer in the Ebro basin, as anticipated under the Hydrological Plan, on the river habitats and biotas, the river mouth, the marine ecosystem and the current uses of the environment. Alternatives and studies required to minimise the impact are also presented
Una primera aproximació biogrà fica a la figura d'Ermenegild Santpau i Bertomeu, il·lustre botà nic català estudiós de la flora i vegetació Ãndies
Changing nutrients, changing rivers
Eutrophication—the excessive enrichment of a body of water with nutrients such as nitrogen (N) and phosphorus (P)—is Earth's most widespread problem for water quality (1, 2). Growing evidence suggests a global trend toward reversing eutrophication. However, in rivers and estuaries of developed countries and in lakes of emerging economies, the ongoing reduction in nutrient inputs—termed reoligotrophication—is much larger for P than for N (3, 4). Although the rapid emergence of this phenomenon has hindered detailed monitoring of the ecological effects, a few studies have documented an abrupt shift from green to clear waters and consequently from phytoplankton to macrophytes as dominant primary producers in response to reoligotrophication in rivers and estuaries (5–7). However, the improvement in water quality due to P decline does not imply a return to pristine ecological conditions, because high N:P ratios trigger undesirable changes in the ecosystem (8).info:eu-repo/semantics/acceptedVersio
Uso del hábitat por una gran población superficial de Pinna nobilis
We investigated the habitat use and size structure of the fan mussel, Pinna nobilis L. in the Alfacs Bay (Ebro Delta, Spain, NW Mediterranean). Shore-parallel transects were conducted to assess the abundance, size, and orientation of individuals and to record habitat features along the Banya Sandspit, at depths of 20 to 130 cm. Results showed two distinctive areas in terms of population density, marked by the end of local salt pan dikes that we named Good Habitat (GH) and Bad Habitat (BH). To extrapolate these results to the full area of BH and GH, perpendicular transects were conducted to determine the local bathymetry. Then, the underestimation of individuals due to the effects of distance, depth and seagrass cover (Distance 6 computer package) was added to raw abundances to obtain a corrected population of 90303 individuals (12085 in the BH and 782018 in the GH), the largest so far reported at such low depths. Most recorded individuals were adults (40 to 60 cm shell length), with no occurrence of sizes < 20 cm, and with a strong association with Cymodocea nodosa seagrass beds. Given the shallow distribution of the population, the absence of small sizes during the study period, and the presence of human activities that may damage P. nobilis and its habitat, the development of a management plan appears imperative for the conservation of the species.El uso del hábitat y la estructura poblacional de la nacra, Pinna nobilis L. fue investigado en la bahÃa dels Alfacs (Delta del Ebro, Spain, Mediterráneo noroccidental). La abundancia, talla, y orientación de los individuos, asà como las caracterÃsticas del hábitat se evaluaron mediante transectos paralelos a la costa, a profundidades comprendidas entre los 20 y los 130 cm. Los resultados evidenciaron la presencia de dos áreas con densidades poblacionales diferenciadas, delimitadas por el final de los diques de las salinas locales, a las que se denominó Good Habitat (GH) y Bad Habitat (BH). Para extrapolar los resultados a toda el área del BH y el GH, se realizaron transectos perpendiculares para determinar la batimetrÃa local. A continuación, las tasas de infravaloración de individuos debido al efecto de la distancia, la profundidad, y la cobertura de fanerógamas marinas obtenidas con el paquete informático Distance 6 se añadieron a los valores no corregidos, y resultaron en una estima de 90.303 individuos (12.085 en el BH y 78.2018 en el GH, la mayor hasta ahora registrada en aguas poco profundas. La mayorÃa de los individuos observados eran adultos (40 a 60 cm de longitud de valvas), sin ocurrencia de tallas < 20 cm, y con una fuerte asociación a la pradera de Cymodocea nodosa. Dada su distribución poco profunda, la ausencia de individuos juveniles durante el periodo de estudio, y la presencia de actividades humanas en la zona que potencialmente pueden perjudicar a P. nobilis y a su hábitat, la implantación de un plan de gestión es prioritario para la conservación de la población local
Environmental flows in the lower Ebro River and Delta: Current status and guidelines for a holistic approach
Deltas are a particular type of estuarine system in which the dependence on river flow (water, sediments and nutrients) is very strong, especially in river-dominated deltas such as the Mediterranean ones, but environmental flow (e-flow) proposals for deltaic systems are scarce. The Ebro Delta is one of the largest wetland areas in the western Mediterranean and one of the most important estuarine systems in Europe. The aim of this paper is to review the state of the art regarding e-flows and to carry out a critical analysis of the proposals for the lower Ebro River and Delta, in order to highlight the possible environmental and socioeconomic impacts arising from the e-flow regime currently approved. Additionally, based on existing scientific information, methods to establish an e-flow regime that allows the maintenance of the main socio-ecological functions and values are discussed; including those functions and values for which not enough information is available. The study concludes that the currently approved e-flows are not suitable for maintaining most functions and values, as they would not prevent the proliferation of alien fish species and macrophytes in the river, the intrusion of the salt wedge in the estuary, the deficit of sediment/nutrient transport and the degradation of riparian habitats or the decline of coastal fisheries. Socioeconomic consequences on coastal fisheries, river navigation, salt water intrusion, sediment deficit, biodiversity, water quality, aquaculture and hydropower are also considered. Other e-flow proposals such as the proposed by the Catalan government would be more suitable to maintain the main socioecological functions and values of the lower Ebro River and Delta. Nevertheless, additional studies are needed to validate e-flows in some relevant aspects such as the capacity of the river to transport sediments to the delta to avoid coastal regression and mitigate the effects of sea level rise and subsidence, as well as the capacity of floods to control the spread of macrophytes. The lower Ebro River and delta is among the case studies where more quantitative and qualitative criteria to set e-flows with a holistic approach have been established.info:eu-repo/semantics/publishedVersio
Pristine vs. human-altered Ebro Delta habitats display contrasting resilience to RSLR
River deltas are ecologically and economically valuable coastal ecosystems but low elevations make them extremely sensitive to relative sea level rise (RSLR), i.e. the combined effects of sea level rise and subsidence. Most deltas are subjected to extensive human exploitation, which has altered the habitat composition, connectivity and geomorphology of deltaic landscapes. In the Ebro Delta, extensive wetland reclamation for rice cultivation over the last 150 years has resulted in the loss of 65% of the natural habitats. Here, we compare the dynamics of habitat shifts under two departure conditions (a simulated pristine delta vs. the human-altered delta) using the Sea Level Affecting Marshes Model (SLAMM) under the 4.5 and 8.5 RCP (Representative Concentration Pathways) scenarios for evaluating their resilience to RSLR (i.e. resistance to inundation). Results showed lower inundation rates in the human delta (~10 to 22% by the end of the century, depending on RCP conditions), mostly due to ~4.5 times lower initial extension of coastal lagoons compared to the pristine delta. Yet, inundation rates from ~15 to 30% of the total surface represent the worst possible human scenario, assuming no flooding protection measures. Besides, accretion rates within rice fields are disregarded since this option is not available in SLAMM for developed dry land. In the human delta, rice fields were largely shifted to other wetland habitats and experienced the highest reductions, mostly because of their larger surface. In contrast, in the pristine delta most of the habitats showed significant decreases by 2100 (~2 to 32% of the surface). Coastal infrastructures (dykes or flood protection dunes) and reintroduction of riverine sediments through irrigation channels are proposed to minimize impacts of RSLR. In the worst RCP scenarios, promoting preservation of natural habitats by transforming unproductive rice fields into wetlands could be the most sustainable option.info:eu-repo/semantics/acceptedVersio
Estructura de la comunidad de macroinvertebrados bentónicos en un estuario mediterráneo altamente estratificado
The community composition and spatial distribution of benthic macroinvertebrates were studied along the Ebro estuary, a highly stratified estuary located in the NE Iberian Peninsula. During the last decade the oligotrophication process occurring in the lower Ebro River and its estuary has allowed a complex benthic macroinvertebrate community to become established; these results contrast with the poor community found there in the early nineties. A total of 214 taxa were identified, and polychaetes dominated the community both in abundance and species richness. The results showed spatial differences in the structure and composition of macroinvertebrates, which suggests that there are two distinct communities along the estuary. Each community was found in a specific stretch (upper and lower estuary) in function of the presence of the salt wedge. The macrobenthos of the upper estuary was dominated by freshwater taxa, but some euryhaline species were also found. The lower estuary showed a marine community typical of shallow Mediterranean environments. The transition between these two communities fits an ecotone model. The highest abundances, richness and diversities were recorded at the lower estuarine stations, especially those closer to the river mouth, whereas the lowest values corresponded to the stations adjacent to the tip of the salt wedge.La composición de la comunidad y la distribución espacial de los macroinvertebrados bentónicos ha sido estudiada a lo largo del estuario del RÃo Ebro, un estuario altamente estratificado localizado al NE de la PenÃnsula Ibérica. El proceso de oligotrofización ocurrido durante la última década en el tramo bajo del rÃo Ebro y su estuario, ha permitido el establecimiento de una compleja comunidad de macroinvertebrados, contrastando con la comunidad encontrada a principios de los noventa. Un total de 214 taxones fueron identificados; los poliquetos constituyeron el grupo dominante en términos de riqueza y abundancia. Los resultados mostraron diferencias espaciales en la estructura y composición de macroinvertebrados, sugiriendo la existencia de dos comunidades diferentes a lo largo del estuario. Cada una de estas comunidades fue encontrada en un tramo especÃfico (alto y bajo estuario) en función de la presencia de la cuña salina. El macrobentos del tramo alto del estuario estaba integrado mayoritariamente por taxones de agua dulce y algunos taxones eurihalinos. Por el contario, el tramo bajo presentó una comunidad marina tÃpica de ambientes mediterráneos someros. La transición entre estas dos comunidades encajó con un modelo ecotonal. Las abundancias, riquezas y diversidades más elevadas fueron registradas en las estaciones del tramo bajo, especialmente en aquellas cercanas a la desembocadura; en cambio, los valores más bajos correspondieron a las estaciones adyacentes al extremo de la cuña salina
La salinidad como el principal factor en la estructuración de comunidades de peces de pequeño tamaño en lagunas costeras mediterráneas hidrológicamente alteradas
In the Ebro Delta coastal lagoons, one of the main anthropogenic pressures is the artificial freshwater input. Each coastal lagoon has different water management schemes causing profound changes in its physicochemical characteristics. The main objective of this water management is to favour some bird species with interest either for conservation or hunting activities. The present study assesses the influence of hydrological alteration on the fish assemblages of three coastal lagoons in the Ebro Delta. The small-bodied fish fauna was mainly composed of five families: Gobiidae, Poecilidae, Cyprinodontidae, Atherinidae and Mugilidae. Salinity was found to be the main factor structuring fish community in the lagoons. The dominant species was the common goby (Pomatochistus microps) when the lagoons reached higher salinity values, whereas the invasive eastern mosquitofish (Gambusia holbrooki) dominated during the period of higher freshwater inputs. The juveniles of the family Mugilidae showed low catch per unit effort, especially during the period of lower salinity. This same pattern was found for the endangered Spanish toothcarp (Aphanius iberus). Overall, introduced species were favoured by low salinity, which highlights the importance of changing the present water management by reducing the freshwater inputs in order to maintain suitable levels of salinity to favour native species that are important for both commercial and conservation purposes.Una de las mayores presiones antropogénicas sobre las lagunas costeras del Delta del Ebro es la entrada artificial de agua dulce. Cada laguna costera presenta medidas de gestión distintas que alteran profundamente sus propiedades fisicoquÃmicas. Esta gestión del agua tiene como objetivo favorecer algunas especies de aves con interés para la caza y/o conservación. El presente estudio evalúa la influencia de la alteración hidrológica en la comunidad de peces de tres lagunas costeras del Delta del Ebro. La fracción de la ictiofauna integrada por individuos de pequeño tamaño estaba mayormente compuesta por cinco familias: Gobiidae, Poecilidae, Cyprinodontidae, Atherinidae y Mugilidae. La salinidad fue el factor que más contribuyó a la estructuración de la comunidad de peces de las lagunas. Con valores máximos de salinidad, la especie dominante en las lagunas fue el Gobito (Pomatoschistus microps), mientras que la Gambusia (Gambusia holbrooki), una especie invasora, fue dominante durante el perÃodo con mayores aportes de agua dulce. Los juveniles de la familia Mugilidae presentaron valores bajos de Capturas por Unidad de Esfuerzo (CPUE), especialmente durante el perÃodo de menor salinidad. El mismo patrón fue encontrado para el Fartet (Aphanius iberus), especie en peligro de extinción. En general, las especies introducidas fueron favorecidas por una baja salinidad, hecho que subraya la importancia de modificar la presente gestión del agua reduciendo los aportes de agua dulce con el fin de mantener niveles adecuados de salinidad que favorezcan a las especies nativas, importantes tanto desde el punto de vista comercial cómo conservacionista
Feeding Habits and Short-Term Mobility Patterns of Blue Crab, Callinectes sapidus, Across Invaded Habitats of the Ebro Delta Subjected to Contrasting Salinity
The blue crab Callinectes sapidus was first observed in the Ebro Delta in 2012 and since then captures have increased exponentially up to over 2 t per day, while its presence remains low in other Catalonian estuarine areas. Here, we use a stable isotope approach (δ15N and δ13C) to explore the dietary habits of adult blue crab in four different invaded habitats—bays, coastal lagoons, rice field drainage channels, and the Ebro River—in order to assess the strength of bottom-up forces and identify risks for native and aquaculture species, as well as patterns of site fidelity (male individuals). Mixing models showed average contributions of 35.89% from organic matter in sediments, 34.25% from animal resources (fish, crustaceans, gastropods, and bivalves), and 23.84% from vegetal resources (aquatic plants and algae), although there were important differences across habitat sites. In sites where bivalves were available, they can represent up to ca. 75% of the diet, thus threatening natural banks and local oyster and mussel farms. The average estimated trophic position of blue crabs in those sites was only 2.8, which confirms an omnivorous behavior but also can be attributed to the fact that mollusks were rare in the majority of the areas sampled in the Ebro Delta. Crabs from the same habitat site exhibited very little isotopic variability, suggesting that they remain in those environments long enough to reflect local salinity conditions. Overall, our results suggest that blue crabs are likely using all locally available resources and remain in certain sites, even when preferred animal preys are scarce and low-quality items are the main dietary option.info:eu-repo/semantics/acceptedVersio
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