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

Abstract

The aim of this study was to evaluate the co-occurrence of some frequent fecal indicator bacteria and cyanobacteria species at San Roque reservoir (SRr), highlighting the relationship between their variability and environmental factors. This study was carried out at SRr (31 22 0 S, 64 27 0 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 Enterococcus spp.) and axenic Microcystis aeruginosa cultures to assess an association among these microorganisms and evaluate whether it was positive or negative. Our results showed an inverse relationship between cyanobacteria and thermotolerant coliform bacteria (TtC) at SRr, which was only observed when high cyanobacteria concentration occurred (!3.4 Â 10 4 to 1.2 Â 10 6 cell.mL À1). Experimental results also showed this type of relationship: E. coli and Enterococcus spp. decreased their growth in the presence of M. aeruginosa. In addition, it was observed that the variability of main phytoplanktonic species and TtC at SRr was mainly explained by temporal patterns, that is, the seasonal changes and the hydrological year. In summary, our data indicated that cyanobacteria high abundance during bloom periods could be an inhibiting factor for bacteria growth at SRr. Moreover, we demonstrated that nutrients such us P and N are not the main factors determining the variability of studied microorganisms in this eutrophic reservoir, but other factors, such as climatic conditions (temperature and precipitations), have a major influence. This study would provide a more comprehensive view on the dynamics of microorganism populations with sanitary relevance in eutrophic reservoirs.

Environmental conditions are more effective than nutrient availability and spatial processes on explaining microphytoplankton functional structure in a subtropical hypereutrophic reservoir

“…Huo et al 2019;Yang et al 2019;Zhang et al 2019;Kutlu et al 2020), including subtropical reservoirs of South America(Bustamante-Gil et al 2012;Beamud et al 2015;Haakonsson et al 2017;Halac et al 2019) and Southern Brazil(Crossetti et al 2013;Moreti et al 2013;Bortolini et al 2016;Cassol et al 2017;Alves et al 2020b), supporting our results.…”

The Effect of Microcystis on the Monitoring of Faecal Indicator Bacteria

“…Halac and colleagues [30] have reported a negative correlation suggesting a similar problem with fecal indicators to the present findings, however, they did not directly measure microcystin and so only infer the effect of toxins based on cyanobacteria levels.…”

Paleolimnological reconstruction of the centennial eutrophication processes in a sub-tropical South American reservoir

“…5). The onset of more stable conditions could have promoted water column stratification, which is optimum for proliferation of cyanobacteria, as noticed in the SRr (Halac et al, 2019;Rodríguez and Ruiz, 2016). This condition combined with increased nutrient concentrations, low-precipitation periods (mid-1950s until the beginning of the 1970s in Fig.…”

“…Intense urban development without adequate infrastructure and planning is largely transforming the catchment. Thus, the main source of pollution is represented by human domestic waste (mainly bacteria and nutrients) as the SRr receives untreated sewage discharges from direct and diffuse sources (Halac et al, 2019). In addition, deforestation and fire cause frequent loss of soil and vegetation in the watershed, increasing the eutrophication process (Rodríguez and Ruiz, 2016).…”