Plant-based single-use packaging alters decomposition and biodiversity patterns in tropical streams

The ecological impacts of plant-based single-use packaging on tropical freshwater ecosystems remain poorly understood. Here, we experimentally evaluated the decomposition rates and invertebrate colonization of emerging plant-based packaging materials (sugarcane bagasse packaging and starch-based bioplastic) compared to native leaf litter in Amazonian headwater streams over 201 days. Using coarse- and fine-mesh litterbags, we found that substrate type significantly influenced both decomposition dynamics, taxonomic diversity and community composition. Sugarcane bagasse decomposes faster than native leaves, particularly in coarse mesh bags, suggesting that its higher biodegradability and microbial processing may result from industrial pre-treatment. In contrast, starch-based bioplastic exhibited the slowest decomposition rates and supported a low-diversity community dominated by generalist taxa. Overall invertebrate abundance, richness and diversity (Shannon and Pielou) did not differ among substrates, leaf litter fostered a distinct composition of aquatic invertebrate species and ecological succession compared to sugarcane bagasse and starch bioplastic. These findings highlight that although plant-based packaging such as sugarcane bagasse may degrade more readily than conventional plastics, its ecological roles diverge markedly from those of natural detritus. Our results underscore the importance of considering substrate quality, invertebrate colonization, and temporal dynamics in environmental assessment of emerging biodegradable materials and plant-based packaging, especially in tropical freshwater systems.