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- Programa de Monitorização dos Ecossistemas Terrestre e Estuarino na envolvente à CTRSU de S. João da Talha - Relatório AnualPublication . Sim-Sim, Manuela; Gordo, Leonel; Brotas, Vanda; Caçador, Isabel; Garcia, César; Neves, Ana; Silva, Teresa; Urriza, Carolina BeltranA equipa responsável por este relatório realizou o programa de monitorização entre Outubro de 1998 e Outubro de 2012, o que permitiu uma boa caracterização dos ecossistemas e evidenciar as principais tendências sazonais e/ou anuais das comunidades biológicas. No presente relatório são apresentados os resultados das diferentes componentes inseridas no programa de monitorização dos ecossistemas terrestre (Flora Epifítica) e estuarino (Fitoplâncton, Vegetação de Sapal, Macroinvertebrados e Ictiofauna). As metodologias seguidas foram idênticas aos períodos anteriores, de modo a permitir uma série temporal das vários componentes estudados do ecossistema.
- Phytoplankton in two tropical mangroves of São Tomé Island (Gulf of Guinea): A contribution towards sustainable management strategiesPublication . C. Brito, Ana; Silva, Teresa; Beltrán, Carolina; Chainho, Paula; de Lima, Ricardo F.Phytoplankton are important primary producers in tropical coastal lagoons, with a critical role in sustaining food webs. However, most studies conducted in tropical systems with high anthropogenic influence have focused only on biomass. Water samples were collected, for phytoplankton (pigments and microscopy) and other environmental parameters, from two mangrove lagoons in São Tomé Island. The highest nutrient concentrations were observed in the mangrove of Praia das Conchas, indicating stronger nutrient inputs in this catchment area. Bottom oxygen deficiency was observed in the mangrove of Malanza, which is likely to be associated with the existence of a bridge that constrains the water exchange with the sea. Pigment analyses showed that overall chlorophyll a concentrations were low, indicating low phytoplankton biomass. The highest values were found at Praia das Conchas. It is suggested that chlorophyll a can be used as an indicator of anthropogenic pressure in this tropical system. Microscopy reveales the presence of Dinophysis sp. and Ostreopsis sp. cells, which can be harmful even at low densities. Water quality could be improved by enhancing oxygen condition in Malanza and by monitoring the occurrence of algal blooms, with potential benefits for public health and tourism.
- Effect of phytoplankton size classes on bio-optical properties of phytoplankton in the Western Iberian coast: Application of modelsPublication . Brito, Ana C.; Sá, Carolina; Brotas, Vanda; Brewin, Robert J.W.; Silva, Teresa; Vitorino, João; Platt, Trevor; Sathyendranath, ShubhaChlorophyll-a satellite products are routinely used in oceanography, providing a synoptic and global view of phytoplankton abundance. However, these products lack information on the community structure of the phytoplankton, which is crucial for ecological modelling and ecosystem studies. To assess the usefulness of existing methods to differentiate phytoplankton functional types (PFT) or phytoplankton size classes from satellite data, in-situ phytoplankton samples collected in the Western Iberian coast, on the North-East Atlantic, were analysed for pigments and absorption spectra. Water samples were collected in five different locations, four of which were located near the shore and another in an open-ocean, seamount region. Three different modelling approaches for deriving phytoplankton size classes were applied to the in situ data. Approaches tested provide phytoplankton size class information based on the input of pigments data (Brewin et al., 2010), absorption spectra data (Ciotti et al., 2002) or both (Uitz et al., 2008). Following Uitz et al. (2008), results revealed high variability in microphytoplankton chlorophyll-specific absorption coefficients, ranging from 0.01 to 0.09 m2 (mg chl)− 1 between 400 and 500 nm. This spectral analysis suggested, in one of the regions, the existence of small cells (< 20 μm) in the fraction of phytoplankton presumed to be microphytoplankton (based on diagnostic pigments). Ciotti et al. (2002) approach yielded the highest differences between modelled and measured absorption spectra for the locations where samples had high variability in community structure and cell size. The Brewin et al. (2010) pigment-based model was adjusted and a set of model coefficients are presented and recommended for future studies in offshore water of the Western Iberian coast.
- Changes in the Phytoplankton Composition in a Temperate Estuarine System (1960 to 2010)Publication . C. Brito, Ana; Moita, Teresa; Gameiro, Carla; Silva, Teresa; Anselmo, Tânia; Brotas, VandaThe main aim of this study was to evaluate the temporal changes in the phytoplankton community of the Tagus Estuary and to identify the stressors involved. Environmental and phytoplankton data were gathered from several studies conducted in the 1960s, 1980s and from 1999 to 2010 (2000s). Phytoplankton data included information on the community composition through microscopy. No significant change was found between temperature and nitrogen values in the three periods. Chlorophyll a concentrations varied throughout the years, and the lowest concentrations were observed after 2004. Significant differences were also found between phytoplankton cell abundances, lower in the 1980s compared to the ones recorded in the 2000s. In the 1980s, diatoms were the most abundant group in the majority of samples and were found to be associated with nitrogen concentrations (canonical correspondence analysis), which was not observed in the 2000s. In the period 2006–2007, the importance of diatoms decreased and smaller cells became more abundant (e.g. cryptophytes, euglenophytes, prasinophytes). The ratio cryptophyta/bacillariophyta seems to yield an increase from <1 in 1980s to >1 in 2006–2007. Mesodinium rubrum and Dinophysis produce recurrent toxic blooms in the adjacent coastal area. We can speculate that the estuary can be a cryptophyte producer to sustain the cryptophytes-M. rubrum-Dinophysis trophic relationship. A top-down hypothesis (shellfish grazing) is considered to explain the change in the phytoplankton community. A quantitative tool, the Phytoplankton Community Index (PCI), yielded a significant deviation of the community, from the 1980s to the 2000s, suggesting a shift toward the dominance of small cells.
- Gymnodinium catenatum Graham isolated from the Portuguese coast: Toxin content and genetic characterizationPublication . Silva, Teresa; Caeiro, Maria F.; Costa, Pedro Reis; Amorim, AnaThe bloom forming marine dinoflagellate Gymnodinium catenatum Graham has been linked to paralytic shellfish poisoning (PSP) outbreaks in humans. Along the Portuguese coast (NE Atlantic), G. catenatum shows a complex bloom pattern, raising questions about the origin and affinities of each bloom population. In this work, the variability within six cultured strains of G. catenatum isolated from Portuguese coastal waters (S coast, W coast and NW coast), between 1999 and 2011, was investigated. The strains were analyzed for toxin profiling and intra-specific genetic diversity. Regarding the toxin profile, differences recorded between strains could not be assigned to the time of isolation or geographical origin. The parameter that most influenced the toxin profile was the life-cycle stage that originated the culture: vegetative cell versus hypnozygote (resting cyst). At the genetic level, all strains showed similar sequences for the D1-D2 region of the large subunit (LSU) of the nuclear ribosomal DNA (rDNA) and shared complete identity with strains from Spain, Algeria, China and Australia. Conversely, we did not find a total identity match for the ITS-5.8S nuclear rDNA fragment. After sequence analysis, two guanine/adenine (R) single nucleotide polymorphisms (SNP 1 and 2) were detected for all strains, in the ITS1 region. This species has been reported to present very conservative LSU and ITS-5.8S rDNA regions, though with few SNP, including SNP1 of this study, already attributed to strains from certain locations. The SNP here described characterize G. catenatum populations from Portuguese waters and may represent valuable genetic markers for studies on the phylogeography of this species.