River confluences are hydromorphologically distinct zones within fluvial networks. These junctions interrupt longitudinal continuity and create localized areas of physical and chemical heterogeneity that can influence ecosystem structure and function. Despite their ubiquity and geomorphic significance, the ecology of confluences remains poorly understood compared to other freshwater habitats. This study examines patterns of macroinvertebrate biodiversity and organic matter decomposition within and around confluences. Field surveys were conducted at 13 tributary–mainstem junctions in Spring 2025, spanning a range of environmental conditions. Leaf litter decomposition was assessed utilizing a standard leaf litter pack design, and quantitative macroinvertebrate sampling was performed to evaluate functional and structural responses in the confluence mixing zone compared to the upstream reaches of both the mainstem and tributary channels. Due to the increased heterogeneity inherent at confluences, it was predicted that both macroinvertebrate diversity and leaf litter decomposition rates would be higher at confluences than in the mainstem river. Preliminary results indicate increased macroinvertebrate diversity at confluences compared to surrounding reaches, whereas decomposition rates varied across locations. These findings suggest that confluences may represent ecologically important nodes of riverine systems but still remain understudied.