Mostrando recursos 1 - 20 de 147

  1. Guadiana River Estuary. Investigating the past, present and future


    Estuaries are some of the most dynamic and complex environments in the world. The places where rivers meet the sea are subject to cycles of constant change – from the waves and currents that move particles of sand and mud every second, to the daily ebb and flow of the tides and the more dramatic effects of periodic floods, droughts and storms. Over thousands of years, estuaries are created, destroyed and re-created by sea-level changes. Few of the earth’s landforms enjoy such a brief and varied existence. The complex interplay between terrestrial, fluvial, coastal and marine realms makes estuaries unique in...

  2. 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 =...

  3. 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...

  4. 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,...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. Palynostratigraphic study of Lower Karoo rocks in the Moatize-Minjova coal basin, Mozambique - preliminary results

    Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Marques, João
    The Karoo Supergroup (KSG) is one of the most important geological units of Southern Africa. The KSG is well represented in the Tete Province along the Zambezi River in several horst and graben basins.

  10. New ordovician palynostratigraphic data of the Phyllodocites Shales Formation, Barrancos region, Ossa Morena zona, Portugal

    Lopes, Gilda; Pereira, Zélia; Piçarra, José Manuel; Fernandes, Paulo
    The Ossa Morena Zone, well represented in the Barrancos region, with Cambrian to Lower Devonian strata. The Ordovician contains from base to top the Barrancos Formation, greenish to purple shale.

  11. Potencial gerador de hidrocarbonetos dos argilitos carbonosos do Karoo Inferior (Pérmico) da Bacia de Moatize – Minjova, Província de Tete, Moçambique

    Fernandes, Paulo; Rodrigues, Bruno; Jorge, R. C. G. S.; Marques, João
    A Formação Moatize na Bacia de Moatize – Minjova é uma unidade importante do Karoo de Moçambique, consistindo em argilitos carbonosos, arenitos e camadas de carvão. Os argilitos carbonosos possuem um importante potencial como rochas geradoras de gás, podendo ser considerados como unidades importante de ‘gás de xisto’. Os valores de %Rr medidos indicam um grau de maturação orgânica compatível com o final da janela do petróleo (ca, 1,35 – 1,4 %Rr). A Formação Moatize é caracterizada por possuir querogénio do tipo II-III e do tipo III, com elevados valores de COT e valores de HI médios a elevados, sendo...

  12. 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...

  13. 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....

  14. 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...

  15. Rochas mãe de hidrocarbonetos da bacia carbonífera de Moatize-Minjova

    Fernandes, Paulo; Marques, João; Rodrigues, B.; Jorge, R. C. G. S.
    A formação de Moatize da Bacia Carbonífera da Moatize-Minjova, é uma unidade estratigráfica importante do Supergrupo do Karoo de Moçambique, consistindo em argilitos carbnosos, arenitos e camadas de carvão.

  16. Palinologia da formação (tilítica) de Vúzi, bacia carbonífeira de Moatize-Minjova, província de Tete, Moçambique

    Lopes, Gilda; Pereira, Z.; Fernandes, Paulo; Marques, João
    Foram obtidos os primeiros dados bioestratigráficos (pólenes e esporos) dos sedimentos glaciogénicos da Formação (Tílica) de Vuzi na sondagem ETA 65, do Karoo Inferior da Bacia Carbonífera de Moatize-Minjova, em Moçambique.

  17. Palinoestratigrafia da sondagem ETA 72 da bacia carbonífera de Moatize-Minjova, província de Tete, Moçambique

    Pereira, Z.; Lopes, Gilda; Fernandes, Paulo; Marques, João
    Apresentam-se os primeiros palinoestratigráficos dos níveis superiores da Formação (Tilítica) de Vuzi e dos sedimentos pós-glaciogénicos da Formação (Gresosa) de Moatize presentes na sondagem E72.

  18. História térmica da bacia carbonífera de Moatize-Minjova

    Fernandes, Paulo; Cogné, N.; Marques, J. M.; Rodrigues, B.; Jorge, R. C. G. S.; Jamal, D.
    Duas sondagens de prospecção de carvão executadas na Bacia Carbonífera de Moatize-Minjova, foram estudadas usando as técnicas do poder reflector da vitrinite e dos traços de fissão da apatite para avaliar a sua história térmica.

  19. 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...

  20. 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...

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.