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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.
- 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.