https://orcid.org/0000-0002-7919-0382
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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′ S, 64°27′ 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 (spring-summer), 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 × 104 to 1.2 × 106 cell.mL−1). 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.
Acknowledgments
We thank Dirección de Seguridad Náutica (Córdoba, Argentina) and Aguas Cordobesas S.A. for supporting in fieldwork and data obtaining. We are also grateful to Sistema Telemétrico and Area de Hidrología (INA - CIRSA) for the supply of hydrological data, and with A.L Rydzewski for regional mapping. Bacteria confirmation was made at University College of Southeast Norway (NSH). A. Montecino, L. Mengo, J. Benedetti, J. Grión, C. Gaido and P. Sánchez helped with maintenance and counting of bacteria and cyanobacteria cultures.
Disclosure statement
No potential conflict of interest was reported by the authors.
Notes on contribuitors
Silvana R. Halac studies continental water systems in order to understand their dynamics and functioning, as well as the impact of anthropic activity on them. The processes of eutrophication, algae blooms, production of toxins and the presence of pathogenic bacteria are the greatest points of interest in these studies. Recently, she has begun the study of sedimentary fill in reservoirs with the purpose of reconstructing the history of the chemical-biological processes that have taken place since their foundation (paleolimnology).
Raquel V. Bazán has a research interest in applied microbiology, limnology and surface water quality. She is also interested in the evaluation of water quality for recreational use and human consumption, the pollution of surface waters and effluent treatment. She is a Professor at the Faculty of Exact, Physical and Natural Sciences – UNC.
Nancy B. Larrosa has a research interest and extensive experience in quality monitoring of water bodies. She also performs transfer technology working, participating and directing agreements for the realization of public service institutions and private companies. She is a Professor at the Faculty of Exact, Physical and Natural Sciences – UNC.
Ana Florencia Nadal is a researcher on Environmental Engineering specialized in wastewater treatment. She studies fecal indicator bacteria populations in natural waters and effluents, transport of pollutants water quality and designing of effluent treatment systems. She is a Professor at the Faculty of Exact, Physical and Natural Sciences – UNC.
Ana Laura Ruibal is a researcher on Hydrology, specialized in Environmental Engineering. She is a coordinator of research and service projects related to water quality and environmental pollution. She also studies cyanobacteria toxins and their effects on human health, including risk assessment in human populations with chronic exposure to cyanotoxins.
María Ines Rodriguez is a researcher on Water Resources, specialized in Limnology, water quality and management. She studies the dynamics of phytoplankton communities and algal blooms, with emphasis on biological indicators. Some studies she has undertaken include the collection and analysis of contemporary data taken from the monitoring of reservoirs and rivers. She is responsible for the permanent program of Water Quality Monitoring and Database management.
Marcia A. Ruiz is a researcher on Water Resources, specialized in Water, Environment and Health Engineering. Her studies focus on toxins produced by cyanobacteria and their effect on human health. The studies carried out include risk assessment in human populations with chronic exposure to cyanotoxins.
Abel G. López is director of the Food Science and Technology Institute. His main area of research is food microbiology with a special interest in microbial control, strategies of microorganism inhibition and food safety. He is a Professor at the Faculty of Exact, Physical and Natural Sciences – UNC.