MICROORGANISMS ASSOCIATED WITH SEDIMENTS IMPACT ON RECREATIONAL WATER QUALITY

HUGO RAMIRO POMA; VERÓNICA RAJAL; CHÁVEZ DÍAZ LUCÍA; WAMAN HARO; DOLORES GUTIÉRREZ CACCIABUE; OSCAR GAMBONI

Singapur

Congreso; IUMS 2017; 2017

Objectives: Recreation is one of the many uses of water natural resources. Depending on the chemical and microbiological quality,recreational aquatic environments, like rivers and lakes, may become a risk to the population. In particular many pathogens includingbacteria, viruses, and parasites may be the source of waterborne diseases. Microorganisms may be adsorbed to solid particles andtransported to a different location or sediment with them into the bed. With that in mind the aims of the study were:1) To select and characterize physico-chemically and microbiologically water and sediments from two different recreational naturalaquatic environments located in Salta, northwest of Argentina.2) To evaluate the importance of sediments as potential reservoir of microorganisms.Methods: Water and sediment samples (3 replicates per occasion) were collected from December 2015 to September 2016 from tworecreational natural aquatic environments: Wierna River (WR, 5 samples: WR1, WR2, WR3, WR4, WR5) and General BelgranoReservoir (GB, 6 samples: GB1, GB2, GB3, GB4, GB5, GB6). Physicochemical variables in water (pH, turbidity, dissolved oxygen,temperature, conductivity, hardness) and sediments (organic matter, humidity, ash, conductivity) were measured. For themicrobiological characterization bacteria and viruses were analyzed. Total aerobic mesophiles (TAM), total (TC) and thermotolerantcoliforms (THC), E. coli (EC), enteroccocci (ENT) and P. aeruginosa (PA) were culture-based enumerated. Bacteria were detachedfrom 2 g of sediments with 20 ml of 1% Tween 80 and 15 min of handshaking. Adenovirus and enterovirus were quantified by realtimePCR from ultrafiltration water concentrates and from sediments after extraction of nucleic acids with commercial kits.Results: The main physico-chemical variations were observed in temperature (according to the season) for both environment,turbidity in WR (2-999 NTU) and dissolved oxygen (WR: 2-7 mg/l, GB: 2-10 mg/l). Culturable bacteria were mainly in the sediments(75-99%) rather than in the water column of each corresponding sample. The highest counts were for TAM in both environments(2.8x103 CFU/ml and 2.4x104 CFU/g for water and sediments in WR and 8x102 CFU/ml and 1.8x105 CFU/g for water and sedimentsin GB). More than 50% of the samples were negative for TC, THC, EC and ENT in water. Although water samples from WR5 andGB2 had the highest bacterial contamination, only in RW2 and GB3 exceeded the limits for EC and ENT established for recreationalwater by the USEPA (2002) (Argentina does not have legislation), being all these associated with rain events. Respecting viruses,only adenovirus was found in WR3 and WR4 water samples and in water and sediments in GB4. In these cases the counts for ENTand EC in water were below the USEPA limits, showing that the presence of virus was not related to the concentration of bacterialindicators.Conclusion: Sediments were the main reservoir of microorganisms. As they can be resuspended and microorganisms returned to thewater column due to the turbulence of rain events or recreational activities, they should also be analyzed at the time the water qualityof a recreational natural aquatic environment is assessed in order to protect public health.