Enhancing national water quality monitoring through biomonitoring: Insights from Uruguay

Biomonitoring is essential for assessing ecological integrity and guiding water-resource management, yet its development in South America remains uneven. This review provides the first integrated synthesis of Uruguay's water quality monitoring and biomonitoring efforts, combining national monitoring programs with three decades of scientific research on fish and macroinvertebrates. We integrated national monitoring data with a systematic review of biomonitoring studies to evaluate spatial coverage, methodological approaches, and environmental representativeness across the six major catchments. Results reveal notable progress in spatial coverage, analytical capacity, and the incorporation of biological assessments. However, our findings also evidenced persistent limitations, including inconsistent protocols, a scarcity of reference sites, heterogeneous taxonomic resolution, and limited representation of large rivers and several key catchments, particularly the Laguna Merín, Río de la Plata West and northwest Río Uruguay basins. Monitoring efforts show clear complementarity: national programs are concentrated in higher-order rivers, whereas scientific studies are predominantly conducted in low-order streams, together improving coverage across hydrological gradients. Although both data sources capture comparable environmental gradients, their integration remains limited. Fish and macroinvertebrate assessments rely predominantly on community-level metrics. The stronger representation of low-order systems enhances the ability to isolate local drivers of degradation, although significant gaps persist in larger river systems. The recent environmental regulatory update (Decree 226/025) offers a timely opportunity to consolidate a catchment-based, ecosystem-oriented biomonitoring framework that formally integrates biological indicators and sentinel species. Based on our synthesis, we highlight priority actions for advancing biomonitoring in Uruguay: developing regionally adapted indices, establishing long-term integrated water quality and biomonitoring programs, identifying minimally disturbed reference sites, and strengthening collaborative efforts between environmental management and scientific biomonitoring studies, advancing on taxonomy training, ecology, and ecotoxicology. Uruguay's institutional coherence and manageable spatial scale position the country to become a regional model for evidence-based freshwater ecosystem monitoring and conservation.