Percorrer por autor "Pereira, Rita"
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- An experimental study of Aurelia aurita feeding behaviour: inference of the potential predation impact on a temperate estuarine nursery areaPublication . Pereira, Rita; Teodosio, Maria; Garrido, SusanaTemperate estuaries are nursery areas for economically important fisheries resources. The common jellyfish Aurelia aurita is a resident species in many of these areas, where it can reach high abundances. This work aimed to determine the potential for predation of A. aurita on zooplanktonic organisms and early life stages of fishes, measuring feeding rates at concentrations that mimic those occurring for zooplankton, fish eggs and larvae in an estuarine nursery area. A set of experiments was aimed at determining the feeding selectivity of jellyfish when offered a mixture of fish eggs and larvae and wild plankton. Clearance rates varied markedly with prey availability and concentrations. When given mixtures of different prey types, jellyfish preferentially elected some taxa (copepods and fish eggs). Data obtained in the laboratory experiments were used to infer the potential impact of jellyfish predation upon zooplankton and ichthyoplankton in the Guadiana estuary (Southern Iberia). Repeated sampling of zooplankton, fish eggs and medusae was undertaken during the summer season of 2011. Abundance determinations were combined with experimentally estimated clearance rates of individual medusa to infer the potential jellyfish-induced mortality on prey in the area. In June and early August jellyfishinduced mortality rates were very high, and half-life times (t1/2) were consequently short for the zooplankton and ichthyoplankton. Although the potentially overestimation of our feeding rates typical of confined laboratory experiments, the results show high ingestion and clearance rates at high temperatures, typical from summer condition, and results also suggest that either by predation on early life stages of fish, or by competition for food resources, jellyfish may have a significant impact on estuarine communities and its nursery function.
- Genotoxicity of copper oxide and silver nanoparticles in the mussel Mytilus galloprovincialisPublication . Gomes, Tânia; Araújo, Olinda; Pereira, Rita; Catarina Almeida, Ana; Cravo, Alexandra; Bebianno, Maria JoãoThough there is some information on cytotoxicity of copper nanoparticles and silver nanoparticles on human cell lines, there is no information on their genotoxic and cytotoxic behaviour in bivalve molluscs. The aim of this study was to investigate the genotoxic impact of copper oxide and silver nanoparticles using mussels Mytilus galloprovincialis. Mussels were exposed to 10 μg L⁻¹ of CuO nanoparticles and Cu²⁺ and Ag nanoparticles and Ag⁺ for 15 days to assess genotoxic effects in hemocytes using the comet assay. The results obtained indicated that copper and silver forms (nanoparticles and ionic) induced DNA damage in hemolymph cells and a time-response effect was evident when compared to unexposed mussels. Ionic forms presented higher genotoxicity than nanoparticles, suggesting different mechanisms of action that may be mediated through oxidative stress. DNA strand breaks proved to be a useful biomarker of exposure to genotoxic effects of CuO and Ag nanoparticles in marine molluscs.
- The effect of distinct hydrologic conditions on the zooplankton community in an estuary under mediterranean climate influencePublication . Petra Muha, Teja; Chícharo, Luís; Morais, P.; Pereira, Rita; Ben-Hamadou, Radhouan; Cruz, Joana; Teodosio, MariaSeveral studies have documented effects of hydrological conditions influencing fish and benthonic communities in estuaries and coastal areas, but only few evidences of freshwater discharge on zooplankton assemblages are found. The major finding of our study in an estuary under climate variability with regulated flow by dams is that increased annual flow leads to an increase in abundance and diversity of zooplankton and decrease of jellyfish blooms. This offers suitable nursery conditions with positive consequences on the food-web functioning. The ecohydrological approach of dual regulation could be useful with controlling the timing, frequency and volume of freshwater inflow by altering dams' operational efficiency, leading to healthy functional environment and optimize adaptability to climatic changes.