Microparticle ingestion by the endangered marine otter (Lontra felina) in a human-impacted coastal ecosystem

Marine pollution by microplastics (MPs) represents a global threat to marine organisms and may pose additional risks to endangered species such as the marine otter (Lontra felina), classified as Endangered both globally and in Peru. This study evaluated the occurrence of microparticles in marine otter scats and the accumulation of plastic waste in three localities along the central coast of Peru: Punta Corrientes, Pucusana, and Ancón. Field surveys were conducted during spring (October 2022) and autumn (May 2023). During each survey, scats were collected and otter presence was assessed through sightings and indirect evidence. Solid waste was qualitatively recorded in areas surrounding otter dens and along the coastline. The scats were processed with KOH to digest the organic material and obtain microparticles which were later tested for polymer identification with µ-Raman spectroscopy. A total of 69 microparticles were identified in scat samples. Pucusana showed the highest proportion (55.07%), followed by Ancón (23.19%) and Punta Corrientes (21.74%). Microparticles were more frequent in spring (59.42%) than in autumn. Fibers were the dominant type (88.41%), and black and blue particles were the most common colors. Polymer analysis of a subsample (56.52%) confirmed polypropylene (PP) in one fiber. No significant differences in microparticle occurrence were detected among localities (χ² = 5.56, p = 0.062). Solid waste, particularly plastic debris such as polyethylene terephthalate (PET) bottles and fishing-related materials, was widely distributed across all sites. These results demonstrate the presence of anthropogenic microparticles in marine otter scats and their co-occurrence with plastic waste in coastal habitats. This study provides baseline evidence of environmental exposure in a top predator and highlights the need for improved waste management and monitoring in human-impacted coastal ecosystems.