Percorrer por autor "Bordalo, M. D."
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- Resilience of an isopod population (Cyathura carinata) to multiple stress factors in a temperate estuarine systemPublication . Bordalo, M. D.; Ferreira, Susana; Cardoso, P. G.; Leston, S.; Pardal, M. A.The Mondego Estuary (Portugal) underwent major modifications in the late 1980s, because of eutrophication, for which it was developed a restoration programme that has been effective in recovering seagrass beds. Recently, this system has been affected by successive weather extremes: floods, droughts, and heat waves. The effect of these multiple stressors on a Cyathura carinata (Isopoda) population has been evaluated, through a long-term data series (16 years) in a seagrass bed, an intermediate area, and a sand flat. A well age-structured and abundant population of C. carinata was observed in the sand flat, in contrast with the seagrass bed and intermediate area. After introducing the restoration measures, C. carinata’s abundance increased even in the stations where it was formerly scarce. This recovery was compromised by successive extreme events. C. carinata declined severely in terms of total abundance and growth production during the 2003 summer heat wave, at the sand flat, also endangering its reproductive success. Floods and droughts affected dispersion of the individuals, which was reflected in the population’s density and production. Nevertheless, this isopod had great resilience, recovering successfully after disturbances. In contrast, the population of C. carinata had less resilience in the seagrass bed and intermediate area, being unable to recover after a succession of disturbances, which may threaten the success of this species in the system. Because the frequency and intensity of weather extremes are expected to continue to increase in a scenario of global climate change, their repercussions will affect such populations, which will have difficulty surviving. This will have severe implications on the functioning of the whole ecosystem.
- Trematode fauna of Hydrobia ulvae (Gastropoda: Prosobranchia) in a eutrophic temperate estuaryPublication . Bordalo, M. D.; Ferreira, Susana; Jensen, K.T.; Pardal, M.A.Digenean trematodes infecting the mud snail Hydrobia ulvae were studied at two key sites of the Mondego Estuary (Portugal), from January 1993 to September 1995: a mud flat covered by the seagrass Zostera noltii, and a bare sand flat where seasonal macroalgal blooms occurred as a result of eutrophication. Digeneans belonging to Microphallidae, Notocotylidae, Haploporidae and Heterophyidae were recorded in snails from both sites whereas representatives from Echinostomatidae were only found in snails from the seagrass bed. The density of infected snails was higher at the seagrass bed than at the eutrophic area partly reflecting the difference in population structure of H. ulvae between sites. The Zostera noltii bed supports an abundant and well-structured mud snail population, with all size-classes represented, in contrast to a less abundant and juvenile dominated population in the eutrophic area. In the Z. noltii bed no clear seasonal and interannual patterns emerged in the infection densities. In the eutrophic area, the density of infected individuals increased in the presence of algae, and decreased during the occurrence of occasional flood events. Small scale spatial and temporal patterns in the prevalence of digenean trematodes in mud snails were therefore demonstrated within the Mondego Estuary that has experienced a mixture of anthropogenic impact and climate instability.