Browsing by Author "Silva, Alexandra"
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- Characterizing phytoplankton biomass seasonal cycles in two NE Atlantic coastal baysPublication . Santos, Mariana; Mouriño, Helena; Calixto De Jesus Moita Garnel, Maria Teresa; Silva, Alexandra; Amorim, Ana; Oliveira, Paulo B.The seasonal and interannual variability of chlorophyll a was studied between 2008 and 2016 in two coastal bays located in the northeastern limit of the Iberia/Canary upwelling ecosystem. The work aims (i) to understand if small latitudinal distances and/or coastline orientation can promote different chlorophyll a seasonal cycles; and (ii) to investigate if different meteorological and oceanographic variables can explain the differences observed on seasonal cycles. Results indicate three main biological seasons with different patterns in the two studied bays. A uni-modal pattern with a short early summer maximum and relatively low chlorophyll a concentration characterized the westernmost sector of the South coast, while a uni-modal pattern characterized by high biomass over a long period, slightly higher in spring than in summer, and high chlorophyll a concentration characterized the central West coast. Comparisons made between satellite estimates of chlorophyll a and in situ data in one of the bays revealed some important differences, namely the overestimation of concentrations and the anticipation of the beginning and end time of the productive period by satellite. Cross-correlation analyses were performed for phytoplankton biomass and different meteorological and oceanographic variables (SST, PAR, UI, MLD and precipitation) using different time lags to identify the drivers that promote the growth and the high levels of phytoplankton biomass. PAR contributed to the increase of phytoplankton biomass observed during winter/midspring, while upwelling and SST were the main explanatory drivers to the high Chl-a concentrations observed in late-spring/summer. Zonal transport was the variable that contributed most to the phytoplankton biomass during late-spring/summer in Lisbon Bay, while the meridional transport combined with SST was more important in Lagos Bay.
- Gender and tobacco consumption among University studentsPublication . Costa, Emília; Godoy, María de los Ángeles Merino; Almeida, Manuela; Silva, Alexandra; Nave, FilipeIn 2019, an estimated 155 million people aged between 15 and 24 were smokers. It is also known that 82.6% of current smokers started smoking between 14 and 25 years old. Tobacco uses in adolescents and young adults can lead to the development of serious and potentially life-threatening health problems. The aim of the present investigation is to identify and describe the practices related to the consumption of tobacco products and their distribution according to gender among students at the University of Algarve. This is an exploratory, cross-sectional study with a quantitative approach. For inferential statistics, a non-parametric analysis (χ 2 ) was performed. The sample consisted of 326 university students, 75.5% female, with an average age of 26.03 years. In this sample, 45% of men and 57.7% of women reported never having smoked. In male students, the pattern of combined consumption is more frequent, with female students preferring conventional cigarettes. Statistically significant differences were found between genders for the pattern of tobacco consumption, the number of colleagues/peers who smoke, the opinion about tobacco-free outdoor spaces and the knowledge about new forms of tobacco/nicotine consumption. The university campus is identified by students as the second space where they most consume tobacco products and where they are most exposed to tobacco smoke. This fact forces a reflection on the strategies to be implemented to develop a healthier university
- Portuguese purse seine fishery spatial and resource overlap with top predatorsPublication . Wise, Laura; Galego, Catarina; Katara, Isidora; Marçalo, Ana; Meirinho, Ana; Monteiro, Silvia S.; Oliveira, Nuno; Santos, Jorge; Rodrigues, Pedro; Araujo, Helder; Vingada, Jose; Silva, AlexandraThe Portuguese purse seine fishery, with average annual catches of 70 000 tonnes, operates mainly in coastal areas and targets small pelagic fish (SPF). Potential competition for resources may occur between the fishery and some species of marine mammals and seabirds, as suggested by observed incidental catches. For those species directly affected by the fishery, the spatial distribution of marine taxa and the fishing fleet are key pieces of information for spatial planning and management. We analysed the spatial and resource overlap between the fishery's distribution and effort, and the distribution and abundance of 6 species of top predators -seabirds (n = 4) and marine mammals (n = 2) between 2010 and 2014. Estimates of annual consumption by top predators and the fishery catch within the distributional range of one of their main prey species (sardine Sardina pilchardus) were also determined. Spatial overlap between all considered species and the fishery was low (<0.221), and only 2 species (common dolphins Delphinus delphis and Cory's shearwaters Calonectris borealis) showed high resource overlap with the fishery (>0.7). Overall, values of consumption of SPF by the top predators were of the same order of magnitude as mean annual purse seine landings for the studied area. Our results can be used for marine spatial planning, including designation of Marine Protected Areas and the development of an ecosystem-based model for the effective management of the Portuguese purse seine fishery that takes into account the consumption of natural predators.
- Temperature and food-mediated variability of European Atlantic sardine recruitmentPublication . Garrido, Susana; Silva, Alexandra; Marques, Vitor; Figueiredo, Ivone; Bryere, Philippe; Mangin, Antoine; Santos, A. Miguel P.The influence of the environmental conditions during larval development on the resulting recruitment strength was investigated for European sardine (Sardina pilchardus) at Atlanto-Iberian waters. Satellite-derived Sea Surface Temperature (SST) and Chlorophyll-a concentration (Chla) data from the previous spawning seasons (January to March/April and October to December of the previous year) were related to recruitment success data in the main recruitment hotspots. Recruitment data was taken from yearly acoustic scientific cruises and from the ICES recruitment index estimated by an age-structured model for the entire stock. A linear discriminant analysis model using SST, Chla, and the abundance of spawners during the spawning season identified years of high and low recruitment for all the recruitment hotspots with an accuracy of >= 79%. In general, high recruitment years were associated with high Chla and low SST, although the most important variables to discriminate between the groups were area-specific. High recruitment years were mostly related to high food availability (Chla), particularly during the last quarter of the previous year. In Western Iberia and in the Gulf of Cadiz, high recruitment years were also associated to lower SST, whereas in the Bay of Biscay, where SST during the winter was generally below the optimal range approximate to 11-12 degrees C for sardine larval development, higher recruitment was associated with high SST. For ICES data of the southern European sardine stock, lower SST and higher Chla during the last quarter of the previous year were associated with high recruitment years and SST alone was able to discriminate between the two recruitment groups with 73% accuracy. Although the time-series of available data are still small, these significant relationships are consistent with field and laboratory studies relating larval growth and mortality with main environmental drivers. These relationships should be further investigated in the following years to evaluate if they can be used to construct reliable indicators to predict the level of recruitment and abundance with sufficient advance to help in the management of this important fishing resource.