Estudo da comunidade microbiana planctônica em um reservatório de região tropical semiárida com ênfase em técnicas moleculares

Abstract

Reservoirs of Brazilian semiarid regions are essential to guarantee water supply to the people who live around them, and the multiple uses change the water quality and the communities of these ecosystems. This study aimed to evaluate the effects of dry and rainy periods during three consecutive years on the density and diversity of the prokaryotic community of the water column in the Armando Ribeiro Gonçalves dam, besides to analyze the fluctuations on some limnological variables. Dissolved oxygen, water temperature and pH were measured with a multiparametric probe (YSI). Sub-samples to the analysis of total phosphorus, phytoplankton density, bacterial and archaeal density determination, and DNA extraction were taken to the Laboratório de Microbiologia Aquática of the Universidade Federal do Rio Grande do Norte. Denaturing gradient gel electrophoresis (DGGE) was used to elucidate temporal shifts on planktonic prokaryotic community of the reservoir influenced by rainy and dry seasons. Bacterial and archaeal abundance and the DGGE band richness were influenced by pluviosity, water temperature, and total phosphorus (TP). Principal components analysis (PCA) showed strong correlations among these variables. Canonical correspondence analysis (CCA) showed temporal shifts on Bacterial and archaeal community composition, associated with the pluviosity, reservoir volume, water temperature, and prokaryotic density. This suggests the predominance of factors associated to precipitation events on community structure determination, that is probably composed by persistent and transitory populations. Considering the set of environmental variables, the results indicated two stability moments in reservoir: one moment when the reservoir volume is smaller; and another when the reservoir volume is greater. These stabilities were broken by the rain and by the water loss, respectively.