Molecular mechanisms of microplastic toxicity in coastal sediments of La Guajira Colombia and emerging ecological risks

Coastal zones are unique transition areas connecting terrestrial and marine environments, recognized to be primary transporters of terrestrial-origin polymeric debris into the oceans. This study is the first attempt to understand the molecular mechanisms of microplastic toxicity in sediments of the most active coastal ecosystems of La Guajira and the environmental implications regarding emerging ecological risks, ensuring maximum coverage to estimate the actual load of your accumulation effectively. The four areas studied show an average abundance of 102 ± 7.86 particles/kg, with a wide variation of 39 ± 15.43, 109 ± 25.45, 211 ± 13.17, and 50 ± 29.56 particles/kg found in Riohacha, Dibulla, Manaure, and Uribia, respectively; the microplastic load was estimated on the coast of La Guajira at 14.71 thousand particles/ton annually, which is considered a moderate level of abundance worldwide. The morphology of the microplastics found was dominated by fragments (55.5 %) and films (29.5 %), showing signs of degradation under high radiation, temperature, and salinity conditions, influencing the surface oxidation rate and the adsorption capacity of contaminants that were identified in three types of polymers by Fourier transform infrared spectroscopy (FTIR), of which polypropylene (PP) was the most predominant, followed by polyethylene (PE) with a heterogeneous spatial distribution associated with factors such as tourism, fishing, and urban activities. The ecological risk assessment based on the pollution load index (PLI) showed a low degree of microplastic contamination; however, hazardous polymers such as polystyrene (PS) can contribute to a high Potential Ecological Risk Index (PERI) and a high Polymer Hazard Index (PHI), which poses a risk to biota and human health, generating concern and requiring appropriate control measures to protect marine ecosystems.