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.