Data of Thesis

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Author: Pedro Lima Sampaio

Title:. Allelopathic interactions between  Microcystis aeruginosa and  Cylindrospermopsis raciborskii isolated from Funil Reservoir, Resende (RJ).

Year: 2011.    Full text (in Portuguese)

Abstract

Allelopathic interactions among phytoplankton microorganisms may play an  important role in the establishment and ma intenance of algae blooms, since they can  suppress the growth of potential competitors, giving competitive advantage for the  allelochemical producer. Evidence suggests that allelopathy influences the shifts in  dominance between  Microcystis aeruginosa and  Cylindrospermopsis raciborskii  blooms in an eutrophic reservoir from Rio de Janeiro, Brazil (Reservatório do Funil).  The aim of this study is to further investigate this possibility. For this purpose one  strain of each species, isolated from the reservoir, w as used on “cross - culture” based  experiments. First, a  Microcystis aeruginosa strain (MiRF - 1) was grown in ASM - 1  enriched with different proportions (10%, 20% and 50%) of the exudate produced by  a  Cylindrospermopsis raciborskii strain (CyRF - 1). The results showed an inhibition of  MiRF - 1 growth in terms of yield, only in the presence of 50% of CyRF - 1 exudate.  Growth rates were not affected. Bigger colony, intense sedimentation and cellular  carbohydrate accumulation were also observed in MiRF - 1 cells on this  condition, but  no effect on chlorophyll - a or microcystin content in MiRF - 1 occurred. Then, the effect  of MiRF - 1 exudate on CyRF - 1 (50% proportionin the medium), was also tested.  However, CyRF - 1 exudate did not affect MiRF - 1, regarding growth or chlorophyll - a ,  under the conditions tested. In addition, no evidence was found that MiRF - 1  produces an allelochemical in response to previous exposition to CyRF - 1 exudate,  under the conditions tested. The results suggest that a possible allelopathic  interaction betwe en  Microcystis aeruginosa and Cylindrospermopsis raciborskii may  influence on intense blooms and niche  separation that takes place in Funil Reservoir. 

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