科研之友
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摘要
O estudo visou avaliar, em um experimento de mesocosmos, a influ那ncia da temperatura e de concentra es de nutrientes na abundancia das algas perif赤ticas (exceto Bacillariophyceae) na plan赤cie de inunda o do alto rio Paran芍. O delineamento experimental constituiu-se de cinco tratamentos: controle (C) e adi o de nutrientes (P+, N+ e NP+) a 25oC, e frio (F) com diminui o da temperatura a 15oC e sem adi ode nutrientes. Laminas de vidro foram utilizadas para coloniza o das algas perif赤ticas, e as amostragens foram feitas entre o 15o e o 31o dia de sucess o. Pela An芍lise de Correspond那ncia Can nica, pode-se observar uma clara separa o entre os tratamentos devido 角 temperatura e adi o de nutrientes. A diminui o de temperatura afetou a abundancia das classes de algas perif赤ticas, principalmente pela redu o da densidade relativa de Cyanophyceae e aumento de Zygnemaphyceae. O enriquecimento artificial de nutrientes, principalmente P, alterou a estrutura da comunidade de algas perif赤ticas, em termos de densidade das classes algais. As densidades relativas das classes, em geral, aumentaram com a adi o de nutrientes. O f車sforo pode ser considerado direcionador na densidade das algas perif赤ticas, como pode ser observado pela r芍pida resposta ap車s os enriquecimentos artificiais. This study set out to evaluate, via a mesocosm experiment, theinfluence of the temperature and concentration of nutrients (N and P) in the abundance of periphytic algae (except Bacillariophyceae) of the upper Paran芍 river floodplain. The experiment was designed using 5 treatments: a control (C), added nutrients (P+, N+, NP+) at 25oC, and without added nutrients at 15oC. Glass slides were used for periphytic algae colonization, and the samples were taken on the 15th and 31st days following colonization. Canonical Correspondence Analysis revealed a clear separation among treatment groups due to temperature and added nutrients. A decrease in temperature affected the abundance of periphytic algae classes, especially in the reduction of the relative density of Cyanophyceae and increase in Zygnemaphyceae. The artificial addition of nutrients 每 especially P 每 altered the structure of the periphytic algae communities. Therelative densities of the classes, in general, increased with the addition of nutrients. Phosphorus may be considered a driver of periphytic algae, as can be seen by the rapid response after artificial enrichment.
