RESEARCH ARTICLE A Survey of Escherichia coli and Salmonella in the Hyporheic Zone of a Subtropical Stream: Their Bacteriological, Physicochemical and Environmental Relationships

The Hyporheic Zone is among the most important interstitial freshwater habitats, but the re-lationship between biotic and abiotic factors in this zone remains under-explored. Entero-bacteria were expected to be present, but no specific studies had ever confirmed this prediction. The aim of this study was, therefore, to evaluate the total coliforms, Escherichia coli and Salmonella spp. in hyporheic water and to determine the relationship of the physi-cal, chemical and environmental factors at different depths in a rainforest stream. To this end, thirty-six water samples were collected at three depths in sites located in the first, sec-ond and third orders in diverse substrates. The total coliforms, Escherichia coli and Salmo-nella sp. were evaluated in terms of their CFU/ml. In the interstitial samples, coliforms were detected in 100 % of the samples. The total coliform counts had higher values at intermedi-ate depths, while E. coli and Salmonella spp. instead had higher values at intermediate and large depths, often reaching or exceeding the values of the surface samples. Our results re-vealed that Salmonella spp. and the coliforms have different microhabitat preferences. Sal-monella spp. and coliform species prefer deposition areas, such as lateral sides of pools