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.

Wetlands are buffers for terrestrial runoff with the essential service of water purification. Despite its importance, they are experiencing degradation due to the combined effect of climate change and poor land-use practices. Studies of natural wetlands in Paraguay are scarce. We assessed wetland water quality conditions using pH, turbidity, total phosphorus (TP), and bacterial indicators of 12 natural wetlands located in protected areas (PW) or in the border of agricultural lands (AW) in the Paraguayan side of the watershed of Parana River. AW presented acidic pH values (x̄=5.5). We registered higher TP values in AW (x̄=0.14 mg/L) compared to PW (x̄=0.06 mg/L). For turbidity AW presented higher and variable values (x̄=425 NTU) than PW (x̄=34 NTU). In connected wetlands as the nutrient flows through the wetlands system to the reservoir concentration decreased 70% (0.1 to 0.03 mg/L) and the turbidity decreased from 112 to 42,6 NTU. This study observed a high degree of variability of bacterial indicators in water and sediment. The counts of coliforms in water and sediment samples were in the order E.Coli>Total coliforms>Fecal Coliforms. Long term contamination by organophosphorus and carbamate pesticides was pointed by the positive results in 100% of the sediment samples. As far as we can conclude wetlands has a key function in ecosystem function, health and preserving the water quality that enters to the reservoir, and protected PW presented better water quality conditions in terms of TP, turbidity, and bacterial indicators.