Mostrando recursos 1 - 20 de 86

  1. Inner shelf paleoenvironmental evolution as a function of land–ocean interactions in the vicinity of the Guadiana River, SW Iberia

    Mendes, I.; Rosa, F.; Dias, J. A.; Schönfeld, J.; Ferreira, Óscar; Pinheiro, J. P.
    This study investigates the land-ocean interactions along the northern margin of the Gulf of Cadiz in the vicinity of the Guadiana River. Benthic foraminifera and sedimentological characteristics were analysed in a sedimentary sequence spanning ca. 5000 years (core 8, 22 m water depth) retrieved from the inner shelf prodeltaic wedge. The analyses were integrated in a temporal framework based on accelerated mass spectrometry radiocarbon dating. Paleoenvironmental changes and sediment transfer mechanisms from the continent to the shelf were investigated and related to climatic oscillations and anthropogenic impact in the region. The results allowed the identification of two main periods of deposition....

  2. Living, dead and fossil benthic foraminifera on a river dominated shelf (northern Gulf of Cadiz) and their use for paleoenvironmental reconstruction

    Mendes, I.; Dias, J. A.; Schönfeld, J.; Ferreira, Óscar; Rosa, F.; Lobo, F. J.
    Same-area comparison between patterns of Recent (living) and Holocene benthic foraminiferal assemblage composition is essential to validate their utility as proxies for paleoenvironmental reconstructions. Such reconstructions have scarcely been attempted in shelf environments. In this study, we compared living (stained), dead and Holocene benthic foraminiferal assemblages from the Gulf of Cadiz continental shelf off the Guadiana River. On average, 99% of the living benthic foraminiferal species were preserved in the dead assemblage and 95% in the fossil record. Several common species were assessed as indicators for certain environmental factors, including river discharge, supply of terrestrial organic matter, heavy metal concentrations,...

  3. Multi-proxy evidence of rainfall variability recorded in subaqueous deltaic deposits off the Adra River, southeast Iberian Peninsula

    Mendes, I.; Lobo, F. J.; Fernández-Salas, L. M.; López-González, N.; Bárcenas, P.; Schönfeld, J.; Ferreira, Óscar
    The Adra River deltaic system, southeast Iberian Peninsula, shows a steep topography and is subjected to strong climatic seasonality. This system has been affected by alternating wet and dry periods, and it has also undergone numerous anthropogenic activities such as deforestation, mining activities, river channel deviations and dam construction, particularly during the last two centuries. Two sediment cores were retrieved off the Adra River, from the western (MS_V9) and eastern (MS_V4) lobes of the subaqueous deltaic deposit. A multi-proxy study was carried out, including grain size, benthic foraminiferal assemblages, magnetic susceptibility and geochemical element analyses, in order to understand the sedimentary...

  4. The morphosedimentary behaviour of a headland–beach system: Quantifying sediment transport using fluorescent tracers

    Oliveira, Sónia; Moura, Delminda; Horta, João; Nascimento, Ana; Gomes, Ana; Veiga-Pires, C.
    Embayed beaches occurring along rocky coasts with headlands controlling hydrosedimentary processes are considered to be constrained sedimentary systems with little longshore sediment transfer between them. Such beaches are likely to narrow under rising sea level and a deficit of fluvial sediment, and because beaches act to dissipate wave energy, cliff erosion is expected to increase. Knowledge of hydrosedimentary processes in fetch-limited environments such as embayed beaches is therefore a fundamental management tool in erosionprone coastal areas such as the Algarve region (southern Portugal). Themain objective of this work is to quantify longshore sediment transport (LST) using a sedimentary tracer and compare the resultswith the ones derived...

  5. The morphosedimentary behaviour of a headland–beach system: Quantifying sediment transport using fluorescent tracers

    Oliveira, Sónia; Moura, Delminda; Horta, João; Nascimento, Ana; Gomes, Ana; Veiga-Pires, C.
    Embayed beaches occurring along rocky coasts with headlands controlling hydrosedimentary processes are considered to be constrained sedimentary systems with little longshore sediment transfer between them. Such beaches are likely to narrow under rising sea level and a deficit of fluvial sediment, and because beaches act to dissipate wave energy, cliff erosion is expected to increase. Knowledge of hydrosedimentary processes in fetch-limited environments such as embayed beaches is therefore a fundamental management tool in erosionprone coastal areas such as the Algarve region (southern Portugal). Themain objective of this work is to quantify longshore sediment transport (LST) using a sedimentary tracer and compare the resultswith the ones derived...

  6. Life history of the common pandora, Pagellus erythrinus (Linnaeus, 1758) (Actinopterygii: Sparidae) from southern Portugal

    Coelho, R.; Bentes, L.; Correia, C.; Goncalves, J. M. S.; Lino, P. G.; Monteiro, P.; Ribeiro, J.; Erzini, Karim
    The common pandora, Pagellus erythrinus, is a commercially important seabream for coastal fisheries in the north and central eastern Atlantic. Age, growth and reproductive aspects of the southern Portuguese population were estimated by analysing 386 specimens ranging in total length (TL) from 12.0 to 44.8 cm. Ages were estimated by counting growth bands on otoliths and verified by marginal increment analysis, with specimens ranging in age from 1 to 21 years. The von Bertalanffy growth function was selected as the most adequate model to fit this species' growth, with the estimated parameters being L-inf = 47.14 cm TL, k =...

  7. Home range, residency and movements of Diplodus sargus and Diplodus vulgaris in a coastal lagoon: Connectivity between nursery and adult habitats

    Abecasis, D.; Bentes, L.; Erzini, Karim
    Acoustic telemetry and standard tag-recapture were used to determine the home range and residency of juveniles and sub-adults of Diplodus sargus and Diplodus vulgaris in the Ria Formosa (Portugal) coastal lagoon. Maximum time between recaptures for the standard tag-recapture method was 128 days for D. sargus and 30 days for D. vulgaris. The majority of the fish were recaptured in the vicinity of the tagging location. Fish tagged with acoustic transmitters had a maximum period of time between first and last detections of 62 days for D. sargus and 260 days for D. vulgaris. Minimum convex polygons areas ranged between...

  8. Fish assemblages of shallow intertidal habitats of the Ria Formosa lagoon (South Portugal): influence of habitat and season

    Ribeiro, J.; Carvalho, G. M.; Goncalves, J. M. S.; Erzini, Karim
    Fish assemblages in seagrass and unvegetated habitats located in shallow intertidal creeks within the saltmarsh area of the Ria Formosa coastal lagoon were sampled with a Riley push net at 3 sites on a monthly basis over a 1 yr period. The objective was to test if both habitats support similar fish assemblages in terms of abundance, diversity, assemblage structure, and size distribution, and to investigate how site and season affect the assemblages. Fish assemblages associated with these habitats were significantly different in terms of diversity, abundance, and assemblage structure. Seagrass supported a larger number of species and greater diversity,...

  9. Feeding habits of the two-banded sea bream (Diplodus vulgaris) and the black sea bream (Spondyliosoma gantharus) (Sparidae) from the south-west coast of Portugal

    Goncalves, J. M. S.; Erzini, Karim
    The stomach contents of Diplodus vulgaris and Spondyliosoma cantharus were: analysed using three simple methods (numeric, gravimetric and frequency of occurrence) and a composite index (I.R.I - Index of Relative Importance). To compare the species, the Schoener index was used. The diet of D. vulgaris consisted mainly of ophiuroids, polychaetes, amphipods and echinoids, while polychaetes, amphipods and hydrozoans dominated in the case of S. cantharus. There were some size-related differences in S. cantharus feeding. Diet overlap was relatively slight, with significant differences in feeding between the two species, notably in terms of greater consumption of echinoderms by D. vulgaris and...

  10. Development of an ecotoxicological protocol for the deep-sea fauna using the hydrothermal vent shrimp Rimicaris exoculata

    Auguste, M.; Mestre, N. C.; Rocha, T. L.; Cardoso, C.; Cueff-Gauchard, V.; Le Bloa, S.; Cambon-Bonavita, M. A.; Shillito, B.; Zbinden, M.; Ravaux, J.; Bebianno, M. J.
    In light of deep-sea mining industry development, particularly interested in massive-sulphide deposits enriched in metals with high commercial value, efforts are increasing to better understand potential environmental impacts to local fauna. The aim of this study was to assess the natural background levels of biomarkers in the hydrothermal vent shrimp Rimicaris exoculata and their responses to copper exposure at in situ pressure (30MPa) as well as the effects of depressurization and pressurization of the high-pressure aquarium IPOCAMP. R. exoculata were collected from the chimney walls of the hydrothermal vent site TAG (Mid Atlantic Ridge) at 3630m depth during the BICOSE...

  11. Genetic differentiation among Parastichopus regalis populations in the Western Mediterranean Sea: potential effects from its fishery and current connectivity

    Maggi, C.; Gonzalez-Wangueemert, M.
    Parastichopus regalis (Cuvier, 1817) is the most expensive seafood product on the Catalonian market (NE Spain), with prices at approximately 130 €/Kg (fresh weight). Despite its ecological and economic importance, biological and genetic information on this sea cucumber species is scarce. Here, we provide both the first insight on the genetic structure of P. regalis using sequences of cytochrome oxidase I (COI) and 16S genes and a morphological description of its population. Individual sea cucumbers were collected in six locations along the Spanish Mediterranean coast, including an area under fishery pressure (Catalonia). We found high haplotype diversity and low nucleotide...

  12. High-resolution digital 3D models of Algar do Penico Chamber: limitations, challenges, and potential

    Silvestre, Ivo; Rodrigues, J. I.; Figueiredo, Mauro; Veiga-Pires, C.
    The study of karst and its geomorphological structures is important for understanding the relationships between hydrology and climate over geological time. In that context, we conducted a terrestrial laser-scan survey to map geomorphological structures in the karst cave of Algar do Penico in southern Portugal. The point cloud data set obtained was used to generate 3D meshes with different levels of detail, allowing the limitations of mapping capabilities to be explored. In addition to cave mapping, the study focuses on 3D-mesh analysis, including the development of two algorithms for determination of stalactite extremities and contour lines, and on the interactive visualization...

  13. Effects of alterations in fresh water supply on the abundance and distribution of Engraulis encrasicolus in the Guadiana estuary and adjacent coastal areas of south Portugal

    Chícharo, Luís; Chícharo, Alexandra; Esteves, E.; Andrade, José Pedro; Morais, P.
    A reduction of inflow to the Guadiana River on the border between Portugal and Spain may directly contribute to the degradation of fish habitats. Changes are expected to the spawning behaviour of Engraulis encrasicolus adults, to the migration patterns of larvae in the estuary, and to the catches of fisheries in the lower part of the river and adjacent coastal areas. Spawning of E. encrasicolus occurs in the lower part of the estuary and in the adjacent coastal areas. However, high abundances of larvae have been registered in the middle and upper parts of the estuary, the most productive region...

  14. Effects of inter-annual freshwater inflow shifts on the community structure of estuarine decapods

    Encarnação, João; Leitão, Tânia; Morais, P.; Piló, David; Range, Pedro; Chícharo, Luís; Chícharo, Alexandra
    The objective of this study was to evaluate how inter-annual changes in freshwater inputs have affected the decapod assemblages in the Guadiana estuary. Three major areas in the estuary were sampled during the summer, in 2001 (high inflow year and before the filling of the Alqueva dam), in 2002 (low inflow and after filling of the Alqueva dam), and in 2008 and 2009 (low inflow and after consolidation of the impacts of the Alqueva dam). A significant increase in total decapod densities was recorded for the entire estuary, but especially in the upper estuary, after the closure of the dam in 2002....

  15. Grazing by Diadema antillarum (Philippi) upon algal communities on rocky substrates

    Alves, F.; Chícharo, Luís; Serrão, Ester; Abreu, A. D.
    Grazing by Diadema antillarum sea urchins is well documented for coral reefs, although information is scarce for the eastern part of the Atlantic Ocean, where rocky substrate dominates the sea bottom. This study analysed grazing activity by D. antillarum upon the algal communities living on rock substrates, and its possible impact on the subtidal communities. Controlled feeding experiments using exclusion cages were performed between May and September 1998 at Madeira Island (NE Atlantic). Three experimental treatments were used: (1) closed cages to exclude sea urchins, (2) open cage controls, and (3) uncaged controls (nine replicates in each treatment). After four...

  16. Reproductive activity and biochemical composition of the pullet carpet shell Venerupis senegalensis (Gmelin, 1791) (Mollusca: Bivalvia) from Ria de Aveiro (northwestern coast of Portugal)

    Joaquim, Sandra; Matias, Domitília; Matias, Ana Margarete; Moura, Paula; Arnold, William S.; Chícharo, Luís; Baptista Gaspar, Miguel
    The present study characterizes the reproductive cycle of Venerupis senegalensis (=V. pullastra) from Ria de Aveiro (Portugal) as well as its nutrient storage and exploitation strategy. The reproductive cycle followed a seasonal cycle that correlated negatively with sea surface temperature, and comprised a ripe stage in winter followed by a spawning period that began in late winter and ended in the early summer. This extended spawning may be an advantageous strategy for the species because it ensures a continuous supply of settlers. Gametogenesis began in late summer/early autumn and intensified with the decrease in temperature during autumn. The condition index...

  17. Comparing the resolution of Bartlett and MVDR processors for bottom parameter estimation using pressure and vector sensor short array data

    Felisberto, P.; Schneiderwind, J.; Santos, P.; Rodriguez, O. C; Jesus, S. M.
    This work compares the resolution of a pressure and vector sensor based conventional Bartlett estimator, with their MVDR estimator counterparts, in the context of bottom characterization with a short vertical array. Santos et al. [1] demonstrated the gain of a vector sensor array (VSA) based linear estimator (Bartlett) for generic parameter estimation. Moreover, it was shown that for bottom characterization the highest resolution of the estimates were achieved with the vertical particle velocity measurements alone. The present work highlights the gain in parameter resolution of a VSA based MVDR estimator. It is shown, that also for a MVDR estimator, the vector...

  18. Devonian and carboniferous palynostratigraphy of the South Portuguese zone, Portugal - an overview

    Pereira, Zélia; Matos, João Xavier; Fernandes, Paulo; Oliveira, José Tomás
    The South Portuguese Zone (SPZ) represents the southern branch of the Iberian Variscides and comprehends the following geologic domains: the Pulo do Lobo Antiform, the Iberian Pyrite Belt, the Baixo Alentejo Flysch Group and the Southwest Portugal (Aljezur and Bordeira Anticlines). An overview of all the results recently achieved in palynostratigraphic research of selected sections all over the SPZ is presented. A chronostratigraphic correlation of the stratigraphic units recognized across the ZPZ and its geodynamic and palaeogeographic implications is attempted.

  19. The Asian clam Corbicula fluminea (Müller, 1774) in the Guadiana River Basin (southwestern Iberian Peninsula): setting the record strait

    Morais, P.; Teodósio, J.; Reis, J.; Chícharo, Alexandra; Chícharo, Luís
    This paper aims to set the record straight regarding the first observations of Corbicula fluminea (Müller, 1775) in the Guadiana River Basin. According to the available data, C. fluminea was first observed in 1988 and not in 2006 as suggested by Pérez-Bote and Fernandéz (2008). The first observations of C. fluminea in the Guadiana estuary were reported in 2000. In 2003, C. fluminea was already well established in the estuary and in many rivers and streams. C. fluminea is likely to expand its current biogeographic distribution in Portugal, since suitable lentic habitats for colonization will be created by the implementation of...

  20. Alien species in the Guadiana Estuary (SE-Portugal/SW-Spain): Blackfordia virginica (Cnidaria, Hydrozoa) and Palaemon macrodactylus (Crustacea, Decapoda): potential impacts and mitigation measures

    Chícharo, Alexandra; Leitão, Tânia; Range, Pedro; Gutierrez, Cristina; Morales, Jesus; Morais, P.; Chícharo, Luís
    The cnidarian Blackfordia virginica and the adult of the caridean prawn, Palaemon macrodactylus are first recorded from the Guadiana Estuary. The habitats and environmental conditions under which these species were found are described and the potential impacts and mitigation measures for their introduction are discussed. The first observations of adults of these species were made in July 2008, at the transitional zone of the estuary (brackish area). Most samples taken in the middle-estuary were characterized by large densities of B. virginica (> 100 individuals 100 m-3), while P. macrodactylus was recorded in much smaller densities (<0.01 individuals m-2). Despite a...

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