Indicator bacteria in subtropical natural wetlands waters

Abstract

Abstract Natural wetlands are transitional ecosystems between aquatic and terrestrial systems. They have a variety of functions, one of the most outstanding being the ability to purify water mainly by microorganisms. Despite their importance, these ecosystems are threatened due to anthropogenic activities, so determining quality indicators is a growing need. Microbial communities respond to leaching, eutrophication, metals, natural or anthropogenic pollutants, and even competition for nutrients with other organisms, making them useful in wetland assessment. There are several bacterial indicators and techniques used to monitor wetlands, including molecular ones, which despite their advantages, remain economically unfeasible to allow long-term monitoring in developing countries. As an alternative, we have determined the bacterial indicators, total and thermotolerant coliforms, Escherichia coli, and Pseudomonasin waters of three natural wetlands corresponding to areas of influence of agricultural and urban activity in Paraguay. Following the membrane filtration method, we obtained bacterial counts for all the indicators (TC max of 210±14 CFU/100mL in a protected zone, FC 15±7 CFU/100mL in a peri-urban area, and E. coli 105±7 CFU/100 mL) except Pseudomonas (<1 CFU/100mL). After analyzing our results, we observed that total coliforms could reflect better environmental conditions. In contrast, fecal coliforms and E. coli would reflect fecal contamination or discharges of nutrients such as phosphorus and nitrogen commonly used in agricultural and urban areas. The absence of Pseudomonascould be due to a non-ideal incubation temperature (37ºC). E. coli, whose growth occurred in all wetlands, together with coliforms, could be a valuable indicator for monitoring these environments.