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

Abstract

The Hyporheic Zone is among the most important interstitial freshwater habitats, but the relationship between biotic and abiotic factors in this zone remains under-explored. Enterobacteria 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 physical, 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, second and third orders in diverse substrates. The total coliforms, Escherichia coli and Salmonella 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 intermediate 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 revealed that Salmonella spp. and the coliforms have different microhabitat preferences. Salmonella spp. and coliform species prefer deposition areas, such as lateral sides of pools, curves and bars, but they have a tendency to distribute into different depths, likely due to temperature differences. Salmonella spp. prefer compact substrata, with fewer fluids passing through and with upwelling areas with lower oxygen inflow. The coliform species showed the opposite preference. Our results suggest that bacterial variation is related to environmental factors and physical-chemical parameters within the HZ and may play a key role in the microbial diversity and distribution in these ecosystems.

Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend

“…The VHG describes the direction and intensity of the water exchange between the hyporheic zone and the surface or the subterranean zone [32]. The VHG varied between −0.41 and 0.01 and −0.25 and 0.04 in July 2015 and January 2016, respectively (Table 2).…”

The hyporheic zone and its functions: revision and research status in Neotropical regions

“…Some microbial communities in elevated concentrations, generally associated of human pollution, were found in superficial water sources in uninhabited rain forests (Rivera et al, 1988). Escherichia coli found upstream of known fecal sources showed a strong positive correlation with water temperature and nutrient concentrations (Carrillo et al, 1985;Jimenez et al, 1989;Mugnai et al, 2015;Rivera et al, 1988).…”

“…As in the mammalian host environment, nutrients in tropical ecosystems are maintained at high concentrations, and together with constant warm temperatures provide an ideal habitat for survival, growth, and proliferation of E. coli (Winfield and Groisman, 2003;Mugnai et al, 2015).…”

“…(Anderson et al, 2005;Fish and Pettibone, 1995;Winfield and Groisman, 2003;Mugnai et al, 2015). Consequently soil and sediment particles can function as microecological niches in which bacterial species can survive and replicate and result in risk for human health.…”

“…Consequently soil and sediment particles can function as microecological niches in which bacterial species can survive and replicate and result in risk for human health. However, these aspects are poorly investigated and represent a crucial point also in those regions worldwide where HZ was better studied (Marmonier et al, 2012;Mugnai et al, 2015 Air,and Soil Pollution,vol. 195,[1][2][3][4] …”