Evaluation of extracellular enzymatic activity in the Aburrá-Medellín tropical river in Colombia as a response to variations in water quality and flow regime, in an urbanized basin

Abstract

The Aburrá-Medellín river has been affected by urbanization processes in its basin, which has altered its physicochemical profile. In order to identify patterns in the enzymatic activity associated with variations in water quality and flow regime, the activity of the β-glucosidase and phosphatase enzymes, related to carbon and phosphorus metabolism, respectively, was measured in the water and biofilm. For this purpose, nine monitoring stations with different degrees of anthropic intervention were selected, which were evaluated during low, medium and high flow regimes associated with meteorological variability in the basin. The hypothesis was that the physicochemical profile, water quality and flow regime affect the activity of both enzymes, both in the water and in the biofilm, since they influence the concentration of nutrients transported by the river. According to the results obtained, no statistically significant differences were found in the enzymatic activity at low, medium and high flow rates, although a higher concentration of nutrients was observed at low and medium flow rates than at high flow rates. On the other hand, it was observed that the concentration of nutrients in the river changed according to the degree of urbanization in the basin, due to the discharge of wastewater from densely populated municipalities. The activity of both enzymes was higher in the stations with higher concentrations of nutrients, while in the monitoring stations located in the upper zone of the basin, where anthropic intervention and the concentration of nutrients was low, the lowest enzymatic activities were found both in the water and in the biofilm. In this regard, enzymatic activity can be used as an indicator of the health of the Aburrá-Medellín river and it is suggested that the measurement of this variable be included in the framework of the RedRío monitoring network.