Diversity of phytoplankton community in different urban aquatic ecosystems in metropolitan Jo o Pessoa, state of Paraíba, Brazil Diversidade da comunidade fitoplact nica em diferentes ecossistemas aquáticos urbanos da regi o metropolitana de Jo o Pessoa, PB, estado da Paraíba, Brasil

AIM: The aim of the present study was to identify which environmental factors affect the seasonal phytoplankton structure in different types of tropical aquatic ecosystems. Phytoplankton sampling was performed bi-monthly from August 2009 to June 2110 at three sites in the Solon de Lucena Lake, Jaguaribe River and águas Minerais reservoir. METHODS: The environmental variables were water temperature, transparency, depth, degree of infestation of aquatic macrophytes, air temperature, wind speed, solar radiation and precipitation. The phytoplankton community was studied in terms of richness, density, diversity and evenness. The data were treated with analysis of variance and canonical correspondence analysis. RESULTS: Spatial variations in the data only occurred between ecosystems (p < 0.05). The reservoir and river exhibited typical phytoplankton of lotic environments, with a greater richness of Bacillariophyta (52.8% and 47.8%, respectively). The lake exhibited the typical richness lentic environments, with the greatest contribution from Chlorophyta (52.8%). This ecosystem was characterized by an absence of macrophytes, a low degree of water transparency (0.3 ± 0 m) and high algal density (89,903 ± 38,542 ind. mL-1), with a dominance of Aphanocapsa nubilum. In the river environment, the lesser diversity (0.64 ± 0.24 bit.ind-1 ) was associated to lesser richness (2.4 ± 0.5 spp.) and lesser evenness (0.39 ± 0.19) in comparison to the other ecosystems. The influence of macrophytes in the river and reservoir contributed toward the introduction of metaphytes and epiphytes in the phytoplankton, which was explained by the direct relationship between the density of these species and macrophytes. CONCLUSION: Thus, water transparency and macrophytes were the main factors related to fluctuations between the different aquatic ecosystems studied. OBJETIVO: Este trabalho visou identificar que fatores ambientais interferem na estrutura sazonal fitoplanct nica em diferentes tipos de ecossistemas aquáticos tropicais. Coletas do fitoplancton foram realizadas bimestralmente de agosto/2009 até junho/2010 em três pontos na lagoa Solon de Lucena, no rio Jaguaribe e no reservatório das águas Minerais. MéTODOS: As variáveis ambientais utilizadas neste estudo foram temperatura e transparência da água, profundidade, níveis de infesta o de macrófitas aquáticas, temperatura do ar, velocidade do vento, radia o solar e precipita o pluviométrica. A comunidade fitoplanct nica foi estudada em nível de riqueza, densidade, diversidade e equitatividade. Os dados foram tratados através de