Water Quality Monitoring in Ecuadorian Streams Using a New Diatom-Based Index

The use of diatoms as ecological indicators of water quality is well established globally, with numerous studies supporting the effectiveness of diatom-based biotic indices for monitoring the ecological status of freshwaters. These metrics typically rely on the relative abundance of “indicator taxa,” their overall sensitivity to impairment, and their environmental optimum along a pollution gradient. In South America, microalgal assemblages have only recently been used to monitor and evaluate the water quality in continental waters. This study aims to design and validate a new diatom metric, the Ecuador Diatom Index (EDI), to enhance water quality assessment in Ecuadorian river basins. The EDI reflects the overall limnological condition of a river, measured through various abiotic parameters integrated into the water quality index. Biological sampling was conducted at 111 stations across the Ecuadorian river basins. Notable differences were observed in floristics and autoecological parameters compared to other diatom-based methods. Statistical analyses revealed that beyond optimum and tolerance, incorporating specific frequency of occurrence and goodness-of-fit to a Gaussian response curve improves the reliability of this metric, surpassing the results of the commonly used specific pollution sensitivity index.