First report on negative association between cyanobacteria and fecal indicator bacteria at San Roque reservoir (Argentina): impact of environmental factors

BAZÁN, RAQUEL; RUIBAL, ANA LAURA; LÓPEZ, ABEL GERARDO; LARROSA, NANCY BEATRIZ; RODRIGUEZ, MARÍA INÉS; HALAC, SILVANA; NADAL, ANA FLORENCIA; RUIZ, MARCIA

JOURNAL OF FRESHWATER ECOLOGY

OIKOS PUBL INC

Lugar: Londres; Año: 2019 vol. 34 p. 273 - 291

0270-5060

The aim of this study was to evaluate the co-occurrence of somefrequent fecal indicator bacteria and cyanobacteria species at SanRoque reservoir (SRr), highlighting the relationship between theirvariability and environmental factors. This study was carried out atSRr (31220 S, 64270 O) located west of the city of Cordoba,Argentina. Physico-chemical measurements and sampling for microbiological and nutrient determinations were done at three recreational sites, during seasons of major touristic activity (springsummer), with the aim of identifying temporal patterns of microorganism variability. In addition, we carried out laboratory experiments with local isolated bacteria (Escherichia coli and Enterococcusspp.) and axenic Microcystis aeruginosa cultures to assess an association among these microorganisms and evaluate whether it waspositive or negative. Our results showed an inverse relationshipbetween cyanobacteria and thermotolerant coliform bacteria (TtC)at SRr, which was only observed when high cyanobacteria concentration occurred (3.4 104 to 1.2 106 cell.mL1). Experimentalresults also showed this type of relationship: E. coli andEnterococcus spp. decreased their growth in the presence of M. aeruginosa. In addition, it was observed that the variability of mainphytoplanktonic species and TtC at SRr was mainly explained bytemporal patterns, that is, the seasonal changes and the hydrological year. In summary, our data indicated that cyanobacteriahigh abundance during bloom periods could be an inhibiting factorfor bacteria growth at SRr. Moreover, we demonstrated thatnutrients such us P and N are not the main factors determining thevariability of studied microorganisms in this eutrophic reservoir, butother factors, such as climatic conditions (temperature and precipitations), have a major influence. This study would provide a morecomprehensive view on the dynamics of microorganism populations with sanitary relevance in eutrophic reservoirs.