Navegando por Autor "Cardoso, Luciana de Souza"
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Artigo Is phytoplankton functional classification a suitable tool to investigate spatial heterogeneity in a subtropical shallow lake?(Elsevier BV, 2012-11-27) Becker, Vanessa; Crossetti, Luciane Oliveira; Cardoso, Luciana de Souza; Rodrigues, Lúcia Ribeiro; Costa, Luciana Silva da; Motta-Marques, David daFunctional groups of phytoplankton are widely recognized to vary in response to certain environmental variables, according to their niche preferences. The aim of this study was to evaluate the strength of the relationship between functional traits of phytoplankton and environmental predictors in a spatially heterogeneous large subtropical shallow lake (Mangueira Lake, southern Brazil), analyzing whether phytoplankton functional approach is a suitable tool to investigate spatial heterogeneity. Samples were taken twice a year (summer and winter), for six years (2001–2006) in the subsurface water at north, center and south sampling stations in that large system (90 km long). This biannual frequency enabled us to evaluate the seasonal and spatial changes of functional groups in relation to environmental variations, by means of ordination analysis (PCA and CCA). The integrated analysis of phytoplankton functional groups and abiotic variables evidenced clear and significant spatial and seasonal gradients (Monte Carlo test, p = 0.01). The seasonal gradient was related to temperature, water-level fluctuations and wind action, leading to spatial heterogeneity of the phytoplankton. The northern part of the lake proved to be dissimilar, with greater availability of soluble reactive phosphorus and higher biomass of phytoplankton. Functional groups related to turbid and mixed environments, such as MP, S1 and J were important. Hydrodynamics-related features were the driving forces for structuring the phytoplankton functional groups, which appropriately showed the main tendencies observed in this ecosystem, proving to be and adequate tool to access spatial heterogeneityArtigo Spatial and temporal variations of Dinophyceae in subtropical reservoirs in southern Brazil(Springer, 2010-08-08) Becker, Vanessa; Cardoso, Luciana de Souza; Fagundes, Paula BragaKnowledge of dinoflagellate diversity in Brazilian reservoirs is limited, especially in subtropical environments. We investigated as to how nutrients and other environmental variables influenced the biomass of Dinophyceae species in three subtropical ecosystems. The reservoirs Samuara, Faxinal, and Sa˜o Miguel were sampled fortnightly from 2002 to 2006, and eight dinoflagellate taxa were identified. High temperature was a determining factor for the occurrence of Peridinium africanum Lemmermann. Peridinium umbonatum Stein and P. willei HuitfeldKass required high concentrations of nutrients. P. willei was inversely related to temperature and directly related to nutrients. P. umbonatum Stein var. umbonatum Stein showed the largest range of tolerance toward resources. Durinskia baltica Carty & Cox and Peridinium gatunense Nygaard could be opportunistic, since they did not show any spatial or temporal patternArtigo Towards a comprehension of Ceratium (Dinophyceae) invasion in Brazilian freshwaters: autecology of C. furcoides in subtropical reservoirs(Springer, 2016-01-28) Becker, Vanessa; Cavalcante, Kaoli Pereira; Cardoso, Luciana de Souza; Sussella, RovanaCeratium species are not a common component of freshwater phytoplankton in South America. However, these dinoflagellates have often been observed in many water bodies over the past two and a half decades. We investigated Ceratium furcoides' abundance and morphological variation during its initial phase of colonization (2012–2013) in two subtropical reservoirs in southern Brazil in order to explore which environmental factors were related to the occurrence, persistence and bloom formation of this dinoflagellate in those environments. Biomass of C. furcoides showed a strong seasonal pattern, in which warm seasons led to an increase in population density, resulting in cell-size reduction, while in the cold seasons cells increased in volume. Maximum densities over 2,500 cells ml-1 were observed in spring–summer periods in both reservoirs. C. furcoides’ abundance in the studied reservoirs was associated, primarily, with a combination of optimal conditions of temperature, organic matter, and pH, and secondarily, with nutrient availability. The possible factors for the successful colonization performed by C. furcoides across distinct Brazilian waterbodies include good swimming performance, low herbivory pressure, and ability to form dense blooms, as strategies that allow maintenance of populations and effective dispersal