10th U6+ Consortium of African Universities International Conference

Land use and land cover (LULC) change is a major driver of freshwater ecosystem degradation, yet its cascading effects on aquatic biota through water quality remain poorly quantified in East African reservoir systems. This study examined (i) the influence of LULC change on water quality, and (ii) the synergistic effects of LULC and water quality on tadpole abundance across three Ziwa Reservoirs differing in surrounding land-use intensity. Physicochemical parameters and nutrients were monitored alongside LULC classification, and tadpoles (n = 12,202) were sampled across sites and seasons. Procrustes analysis revealed a significant concordance between LULC gradients and water quality profiles (m² = 0.361, p = 0.001), confirming that catchment-level land-use intensification directly reshapes reservoir water chemistry. Hurdle generalized linear mixed models showed that elevated nitrite (OR = 4.10, p = 0.003) and ammonium (OR = 3.40, p = 0.021) concentrations, both linked to LULC-driven nutrient loading, significantly increased the odds of tadpole presence. Notably, a dissolved oxygen threshold near 2 mg/L functioned as a habitability cutoff, below which tadpoles were effectively excluded, with reactive nitrogen compounds predicting population dynamics above this threshold. These findings demonstrate a hierarchical threshold-mediation pathway linking LULC intensification to reservoir habitability for anuran larvae, offering a mechanistic basis for using tadpole assemblages as bioindicators of aquatic ecosystem health under land-use change.