Characterization of cyanobacteria present in Yacyretá dam blooms (Argentina)

LLANO, V.; BERÓN, C.M.; DOMÍNGUEZ, S.; CANEO, M.; ANDRINOLO, D.; MEICHTRY DE ZABURLIN, N.; SALERNO, G.

Río Das Pedras, Brasil

Congreso; VII Conferencia Internacional sobre CianobacteriasTóxicas; 2007

Harmful cyanobacterial blooms have been increasing during the last decade in South America. Particularly, in the Paraná River an enhancement in the density and permanence of cyanobacterial blooms has been registered in the last years, associated to eutrophication processes. It is also evident that the number of cyanobacterial species, which may produce toxins, is increasing in the region, as it is the number and variety of toxins. Since the summer of 2004, at the Yacyretá dam, located on the Alto Paraná (27° 28´ S, 56° 44´O), an increase of the frequency of blooming was observed. Consequently, the isolation and characterisation of cyanobacteria present in each episode and the cyanotoxins they produce in a systematic program is of relevance. The present work shows the first results of an integrated study comparing the cellular density, toxin levels, physical parameters as well as microscopical and molecular identification of cyanobacterium species present in blooms. A seasonal sampling was made in the left shore of the Yacyretá dam that exhibited more favorable conditions for its development. Cyanobacteria, represented by 11 different taxa, were more abundant in summer and spring. The density changed between 0 to 49,192 cells per ml, being Microcystis aeruginosa the most abundant and the only producer of blooms. Closely related genotypes of M. aeruginosa were identified using PCR methodology by amplification of the PC-ING and rRNA-ITS regions. Cyanobacterial communities showed different relative abundance between bloom stages. Also, identification and quantification of cyanotoxins were made by HPLC (HP 1100, C18 column, 238 nm UV detection), comparing the samples with analytical standards for RR, LR, XR and YR microcystins, and nodularins. Toxin production is mainly represented by microcystins. Supported by ANPCyT (PICT 2004 Nº 21227/53), CONICET (PID 6105), UNaM, Yacyretá, and FIBA.