Beyond abiotic decay: Fiddler crabs accelerate plastic fragmentation in pollution hotspots

Mangrove forests are recognized as hotspots for plastic sequestration, especially in urbanized areas where plastic litter can be up to two orders of magnitude more abundant. Fiddler crabs, important ecosystem engineers, are thriving in these plastic-rich environments, raising questions about how they interact with high plastic loads in the sediments they inhabit and feed upon. To explore this, we conducted a field exposure experiment in polluted urban mangroves along the southern Caribbean coast of Colombia, inhabited by Minuca vocator. Fluorescently labeled polyethylene microspheres—small (green, 20–27 μm) and large (red, 75–90 μm)—were introduced to mimic the size range of food particles. The experiment tracked microsphere uptake over 66 days in crab tissues (hepatopancreas, gills, and hindgut) and surrounding sediments. Quality assurance and control tests were also conducted to evaluate potential fragmentation sources that could affect results. The exposure experiment was approved by the Comité de Ética para la Experimentación con Animales -Universidad de Antioquia (according to minute 154, issued on 8th August 2023) and the collection and mobilization of samples was performed under the “Permiso Marco de Recolección de Especímenes de Especies Silvestres de la Diversidad Biológica con Fines de Investigación Científica” awarded to Universidad de Antioquia by Resolution 0524 (Autoridad Nacional de Licencias Ambientales).