From species-specific behaviour to ecosystem risk: Upscaling our understanding of microplastic impacts on marine soft sediment ecosystem functions

Evidence of microplastic-ecosystem impacts is growing; however, our capacity to evaluate associated risks to Earth system processes remains limited. Upscaling impacts and risk assessment in the natural environment usually require a careful balance of accuracy and precision accounting for heterogeneity in ecosystem processes. Intermediate steps between controlled experiments and broad-scale prediction are necessary to fully appreciate the magnitude and implications of plasticising the planet. We explored the potential to change critical ecosystem feedback processes and how these effects can propagate across heterogeneous habitats on intertidal flats. Microplastics (>0.0002 g cm) shrank the bioturbation hotspots by 65% at maximum, affecting the landscape of M. stewartensis in regulating the remineralisation across the surveyed sandflat. Behavioural changes in key species can cascade through their functional roles in regulating food resources, thereby amplifying the impacts of microplastics on habitat degradation. This conceptual framework provides a basis for integrating ecosystem feedback into microplastic risk evaluation.