Bacteriological and environmental state of Pampean Shallow lakes associated to the Salado River (Argentina)

SAGUA, MARA; NUOZZI, GUILLERMINA; PERDOMO, SANTIAGO; SÁNCHEZ, MARÍA LAURA; BIANCHELLI, JULIETA; IPUCHA, DIEGO; SCHIAFFINO, MARÍA ROMINA

Congreso; ISME Virtual Microbial Ecology Summit; 2020

The Salado River Basin is located in central Pampa Plain (Argentina), one of the most productive areas in the country. This is a densely populated area, characterized by their shallow, eutrophic and polymictic lakes. These aquatic ecosystems are strongly influenced by human activities, while providing natural resources for fishing, irrigation and tourism. The main objective of this work was to evaluate the presence of fecal indicator bacteria(total coliforms -TC- and Escherichia coli), as well as to assess several aquatic environmental and biological variables in each lake (Secchi depth, temperature, dissolved oxygen, pH, conductivity, turbidity, organic and inorganic suspended solids, soluble reactive phosphorus ?SRP-, ammonium and chlorophyll a). The land use in the surrounding areaof each water body (categorized as agriculture, livestock, urbanization and wetlands) was also determined. Samplings were carried out on 23 sites from 14 shallow lakes connected to the Salado River during October 2019. Principal component analysis revealed a separation of the shallow lakes by subbasins (upper and lower). Shallow lakes from the upper sub-basin were ordinated according to agricultural use and increasing SRP values, whilethose of the lower sub-basin were ordinated according to livestock use. In concordance, Kruskal- Wallis analyses showed that the agricultural and livestock areas were statistically different between both sub-basins (p<0.001); and also revealed significant differences between sub-basins for SRP, conductivity and oxygen (p<0.05). SRP also showeda positive correlation with agricultural use (r=0.60; p< 0.005). No significant correlations were found between E. coli or TC with any of the measured variables. The presence of E. coli and TC highlighted the influence of specific events of urban and livestock effluent discharges. Together, our results suggest that land use exerts an influence on the bacteriological and environmental state of these shallow lakes.