Monitoring microplastics in live reef-building corals with microscopic laser particles

Micro- and nanoplastics pose a growing threat to marine organisms, such as reef-building corals. Yet, our understanding of microplastic uptake, interaction with coral tissue, and incorporation into coral skeletons remains limited, mainly due to the invasiveness of existing methods for detecting microplastics. Here, we exploit optical resonances in polymer spheres to transform microplastic particles into microscopic lasers. The bright, distinctive, and stable spectral signatures emitted by the microscopic laser particles function as optical barcodes, allowing extended tracking of microplastics transport through optically opaque coral tissue. Simultaneously, the lasers provide real-time sensing of dynamic changes at the microplastic surface with nanoscale resolution. Using confocal hyperspectral imaging, we establish the technical and analytical framework to capture coral anatomy and combine tracking and surface sensing into an integrated, non-invasive approach. With this, we explore the transport and internalization of individual microplastics in live corals, opening new avenues for understanding their ecological impact.