Ecological quality index using periphytic algae in San Juan river (Antioquia-Colombia)

Objetive. This work evaluated the environmental condition of a section of the San Juan River by means of the ecological quality index (ICE), using as an indicator group the periphytic algae. Materials and methods. The method determined correlations between physicochemical and biological variables through a canonical correspondence analysis, the scores obtained were used in a standardized correlation for a weighted averages model that allowed estimating the optimum and the tolerance of each taxon. Results. The classification of the sites located in the section of the River using the ICE explained that the concentrations of dissolved solids, alkalinity and orthophosphates defined the categories of ecological status, it was identified that at higher concentrations of dissolved solids and orthophosphates and at lower concentrations of the alkalinity values of the ICE were lower, that is to say, the ecological quality of the periphytic algae decreases, this situation took place in two seasons characterized by turbid waters and anthropic intervention. In contrast, another group tended to register the contrary tendencies, a greater concentration of alkalinity and high values in the index. Conclusions. The index provided an objective response to evaluate in numerical form a gradient associated with the concentration of solids, nutrients and alkalinity, variables that affect the distribution of optimal values and tolerance of the periphytic algae to the physicochemical conditions evaluated by the ICE in a stretch of the San Juan River, the results suggest a progressive deterioration of the system from the headwaters to the mouth of the Cauca River.