University Of Tehran Press Pollution 2383-451X 11 2 2025 02 01 Diatom-based Index: A tool for Assessing Water Quality in A Southeast Asian Tropical River Basin 298 311 99853 10.22059/poll.2024.378540.2437 EN Reggie Ladera Xavier University – Ateneo de Cagayan, Cagayan de Oro City, 9000, Philippines Astrid Lara Sinco Xavier University – Ateneo de Cagayan, Cagayan de Oro City, 9000, Philippines Judy Pacturan Sendaydiego Xavier University – Ateneo de Cagayan, Cagayan de Oro City, 9000, Philippines Leolinda Lomongo Saab Xavier University – Ateneo de Cagayan, Cagayan de Oro City, 9000, Philippines Carl Ian John Sabaldano Hallazgo Xavier University – Ateneo de Cagayan, Cagayan de Oro City, 9000, Philippines Ester Lara Raagas Xavier University – Ateneo de Cagayan, Cagayan de Oro City, 9000, Philippines Journal Article 2024 06 26 Diatoms are key components of freshwater ecosystems, serving as primary producers and indicators of ecosystem health. Twenty-eight rivers and streams within a Southeast Asian River basin were sampled for diatoms and physicochemical conditions. Diatoms and local standards of physicochemical conditions were analyzed using canonical correspondence analysis. A diatom-based index was developed using pollution values of taxon (PVT) generated using physicochemical conditions and local limits. The CCA revealed that some diatoms responded to local standards, reflecting environmental conditions. Axis 1 is characterized by nutrient related variables explaining 33.04% of the species-physicochemical relationship while Axis 2, characterized by chemical gradients, explains 21.26%. PVT values profiled diatoms in terms of tolerance. Higher PVT are indicative of higher tolerance for disturbance while lower PVT indicate sensitivity. Achnanthidium, Fragilaria, Gomphoneis, Gomphonema, Luticola, Navicula, Nitzschia, Pinnularia and Surirella had the highest PVT values indicating high tolerance to disturbance. These taxa occupy wide ranges of environmental conditions. Genera like Sellaphora and Pleurosira had the lowest PVT values and are found in narrow niches. Majority of the areas are moderately disturbed based on the developed index. Moderate and low disturbance areas are recommended for prioritization in conservation efforts since they may still be reversible in terms of disturbance levels. Low disturbance areas may serve as reference sites for good water quality and ecological status of the river basin. The development of a diatom-based index encourages the use of diatoms for routine water quality and ecological assessments in local Southeast Asian River basins. https://jpoll.ut.ac.ir/article_99853_53e8751a142caa0d0c58c7c52e2c2a0f.pdf