Phytoplankton has an essential role as a primary producer in lakes, providing information on environmental conditions and water quality. The objective of this research was to inventory, characterize, and assess the diversity of microalgae in the Quimsacocha lake system in Azuay, Ecuador. Water samples were collected from the two most important Quimsacocha lakes to morphologically characterize the microalgae and evaluate their diversity. The diversity and physicochemical parameters were measured to evaluate and explain differences in community richness and composition using multivariate analysis (NMDS and PERMANOVA). The level of organic pollution in the lakes was estimated using the Pollution Index, and the trophic status was assessed using dominant phytoplankton (AARL-PP Score). Eighty morphospecies were identified within 25 genera, 16 families and 8 classes. The Bacillariophyceae class was the most diverse, represented by five families. The genera Synedra, Chlorella, and Cosmarium were the most abundant, suggesting a moderate level of organic pollution and a mesotrophic state in the lakes. Physicochemical parameters such as temperature, pH, dissolved oxygen and electrical conductivity were similar in both lakes. Nonetheless, the lake depth was different, varying between 0.9 and 8 m in LQA (with one extreme value of 22 m), compared to LQB, which had depths between 7 and 19 m. Alpha diversity revealed a significant difference (p = 0.0001) in species abundance between the two lakes, while specific richness was similar (p = 0.8213). In terms of beta diversity, a significant difference in species composition was observed (p = 0.001). This study provides base-line information regarding the ecological status of these Andean lakes, being of great help in developing conservation plans to preserve their biodiversity and water quality for human consumption.

Water chlorination, fundamental for its microbiological safety, generates by-products, such as trihalomethanes (THMs), potentially associated with carcinogenic and reproductive risks. This study determined the levels of chloroform (CHCl₃) in drinking water in Cuenca, Ecuador, a topic that has been little explored in the region. During five months, water samples were collected from three water treatment systems (Cebollar, Tixan, and Sustag), and in situ measurements of physicochemical parameters such as free chlorine, pH, temperature, electrical conductivity, and turbidity were performed in the storage and distribution area. The determination of CHCl₃ was performed following the Hach protocol. For data analysis, the Kruskal–Wallis test was employed, followed by Dunn’s post hoc method and Spearman’s correlation coefficient. The results revealed a progressive decrease in free residual chlorine throughout the distribution systems. CHCl₃ concentrations ranged from 11.75 µg/L to 21.88 µg/L, remaining below the Ecuadorian regulatory limit of 300 µg/L. There was no consistent correlation between CHCl₃ and physicochemical parameters. These findings align with previous research, suggesting that the variability in CHCl₃ formation is associated with different water treatment conditions and environmental variables. This study highlights the importance of monitoring disinfection processes to minimize THMs and other DBPs, ensure public health, and contribute to sustainable drinking water management in Ecuador.