Bittencourt-Oliveira M C, Dias S N, Moura A N, Cordeiro-Araújo M K, Dantas E W
Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba, SP, Brazil.
Braz J Biol. 2012 Aug;72(3):533-44. doi: 10.1590/s1519-69842012000300016.
Environmental conditions favor the predominance of dense populations of cyanobacteria in reservoirs in northeastern Brazil. The aim of this study was to understand cyanobacterial population dynamics in the rainy and dry seasons at two depths in the Arcoverde reservoir. Microalgae and cyanobacteria samples were collected during 24 hours with intervals of 4 hours (nycthemeral) at sub-surface and 10 m using a van Dorn bottle and a determined biomass. Physical and chemical variables were obtained and the data were analyzed using the principal component analysis (PCA). No nycthemeral variations in the taxonomic composition or distribution of the populations of cyanobacteria were found between the different times of day in either the rainy or dry season. In both seasons, the greatest biomass of the phytoplankton community was made up of cyanobacteria at two depths and all times of the day. Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju was dominant at all times of the day on both the surface and at the bottom. In the rainy season, the differences in cyanobacterial biomass between the surface and bottom were less significant than in the dry season. The differences in cyanobacterial biomass between surface and bottom were less pronounced than those found in the dry season. We concluded that a) physical variables better explain the alterations of species in the phytoplankton community in an environment dominated by cyanobacteria throughout the year; b) seasonal climatic factors associated to periods of stratification and de-stratification are important for alterations in the community and variations in biomass and, c) the turbidity caused by rainfall favored the emergence and establishment of other cyanobacteria, especially Planktothrix agardhii (Gomont) Anagnostidis & Komárek.
环境条件有利于巴西东北部水库中蓝藻大量繁殖。本研究的目的是了解阿科韦尔德水库在雨季和旱季两个深度的蓝藻种群动态。使用范多恩采水器在水面以下和10米深处每隔4小时（昼夜）采集24小时的微藻和蓝藻样本，并测定生物量。获取了物理和化学变量，并使用主成分分析（PCA）对数据进行分析。在雨季或旱季的不同时间段，未发现蓝藻种群的分类组成或分布存在昼夜变化。在两个季节中，浮游植物群落的最大生物量在两个深度和一天中的所有时间均由蓝藻组成。柱孢藻（Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju）在水面和水底全天均占主导地位。在雨季，表层和底层蓝藻生物量的差异不如旱季显著。表层和底层蓝藻生物量的差异不如旱季明显。我们得出以下结论：a）物理变量能更好地解释在全年以蓝藻为主导的环境中浮游植物群落物种的变化；b）与分层和去分层时期相关的季节性气候因素对群落变化、生物量变化很重要；c）降雨引起的浊度有利于其他蓝藻的出现和定殖，尤其是席藻（Planktothrix agardhii (Gomont) Anagnostidis & Komárek）。
