Dados da dissertação de mestrado
Author: Iame Alves Guedes
Title: Diversity and Dynamics of Cyanobacteria and Microcystin production at Funil-RJ Reservoir
Year: 2013. Full text (in Portuguese)
Abstract
The Funil reservoir is located in Resende, RJ and presents frequent cyanobacterial blooms. The aim of this study was to analyze the diversity of cyanobacteria and their temporal dynamics during a bloom in the Funil reservoir, as well as the production of microcystins (MC), using different approaches. Water samples were collected from October 2011 to April 2012 and the largest values of phytoplankton biomass were detected in samples of October (5.7 mm3 .L-1 ), December (7.6 mm3 .L-1 ) and February (5.8 mm3 .L-1 ). Cyanobacteria dominated throughout the period and contributed with 88% to 99.8% of the phytoplankton biomass. The major taxa found were Microcystis spp., Cylindrospermopsis raciborskii and Dolichospermum sp. We observed the alternation of dominance between these three taxa, where Microcystis spp was dominant on October and December, C. raciborskii samples on January and Dolichospermum sp. on February samples. Phytoplankton biomass correlates positively with Microcystis biomass , NH4 + , chlorophyll and pH and negatively with NO3 - and DIN. MC was detected in all samples, including three isoforms, MC-LR, RR and YR, and concentrations ranged from 589.9 to 72.8 ng.L-1 . The proportion of Microcystis genotypes potentially producing MC was measured by qPCR and high variation was observed , ranging from 9 to 100%. Genetic diversity of cyanobacteria was evaluated by means of cpcBA sequences from each month. We sequenced 204 clones and observed 58 genotypes. Of these, 48 were genotypes of Microcystis, 7 Cylindrospermopsis 1, Pseudoanabaena and 1 Dolichospermum; 44 unique sequences were found. One Microcystis genotype was observed in all samples, 2 occurred in 5 months and the majority only in 1 or 2 months. The cpcBA marker was useful to distinguish cyanobacteria genera and to reveal intraspecific variability, but the analysis did not support species assignment in the Microcystis genera.
Links
 |