Freshwater IMTA systems are increasingly promoted as sustainable aquaculture models because they improve nutrient recycling and support biomass production across multiple trophic levels. However, the consequences of microplastic contamination for the overall productivity of such systems remain insufficiently understood.
In this study, we experimentally evaluated the effects of polyethylene microplastic exposure delivered through feed, water, and combined pathways in a freshwater IMTA system composed of rainbow trout (Oncorhynchus mykiss), freshwater mussels (Unionidae), and duckweed (Lemna minor). The exposure phase lasted 45 days and was followed by a 45-day depuration period.
The results showed that microplastic exposure generated measurable but route-dependent effects across trophic compartments. Fish growth responses were modest overall, although transient reductions in average daily gain and feed efficiency were observed in exposed groups during the exposure phase. Freshwater mussels showed lower per-capita filtration performance under combined exposure, while duckweed biomass production was reduced most clearly in the combined treatment. When these responses were integrated at the system level, the combined feed- and water-borne exposure produced the greatest reduction in overall IMTA productivity.
These findings suggest that microplastic contamination may alter biomass distribution and functional performance in freshwater integrated aquaculture systems, especially when multiple exposure routes occur simultaneously. The study contributes to a better understanding of how emerging contaminants influence sustainable aquaculture design, trophic interactions, and system resilience.