From Indicator to Prediction: Five Decades of Biochemical Oxygen Demand Research in Tropical Freshwaters

Vollständiger Abstract

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ABSTRACT Biochemical oxygen demand (BOD) remains a core indicator of organic pollution in freshwater monitoring, but its role in water policy and practice is changing as water‐quality assessment moves toward predictive, integrative, and decision‐support approaches. This transition is particularly relevant in tropical freshwater systems, where high temperatures, hydrological seasonality, rapid land‐use change, urban expansion, agricultural intensification, and wastewater‐treatment deficits can intensify organic loading, microbial respiration, oxygen consumption, and hypoxia risk. We conducted a bibliometric and topic‐modeling synthesis of 419 peer‐reviewed articles published between 1972 and 2024 and retrieved from Scopus and Web of Science. Latent dirichlet allocation was used to identify thematic structures, and temporal trends in topic prevalence were evaluated to assess shifts in the scientific role of BOD in tropical freshwater research. Four major thematic axes were identified: i) water‐quality prediction and parameter modeling; ii) ecological impacts and heavy metal pollution in streams; iii) oxygen demand and wastewater treatment in lakes and wetlands; and iv) index‐based assessment of water quality in reservoirs. The strongest emerging trend was the increasing prominence of prediction and parameter modeling, indicating that BOD is increasingly being incorporated into machine‐learning models, water‐quality indices, sensor‐based monitoring, spatial analyses, and decision‐support systems. BOD research in tropical freshwater systems is shifting from a primarily descriptive and compliance‐oriented indicator toward a reference variable within predictive, integrative, and policy‐relevant monitoring frameworks. However, BOD also has important limitations as a predictive tool, including incubation delay, context dependence, sensitivity to microbial and environmental conditions, and limited transferability across basins. We argue that BOD should remain a core regulatory benchmark, but its future value in tropical water governance depends on integration with high‐frequency physicochemical monitoring, hydrological data, ecological indicators, land‐use information, locally validated predictive models, and open decision‐support platforms capable of supporting early warning, wastewater management, monitoring prioritization, and adaptive freshwater policy.