Harmonized efforts for the assessment of microplastic contamination trends using 210Pb dated sediment cores from an urbanized coastal lagoon (NW Mexico)

Sediments are microplastics (MP) sinks, capturing long-term accumulation and historical anthropogenic impacts. The analysis of ²¹⁰Pb-dated sediment cores offers temporal insights for evaluating MP pollution trends in coastal ecosystems, aligning with UN Sustainable Development Goal (SDG) 14.1.1b, which seeks to reduce marine pollution through enhanced monitoring and assessment practices. As part of the Research Network of Marine-Coastal Stressors in Latin America and the Caribbean (REMARCO), our efforts contribute toward harmonizing plastic pollution monitoring across the region using nuclear and isotopic techniques. Through the regional project RLA7025, supported by the International Atomic Energy Agency (IAEA), we examined three sediment cores to assess temporal variations in MP abundance (particles kg¯^¹) and flux (particles m¯^² year¯^¹) over the past century in the coastal lagoon Estero de Urias, in the Mexican Pacific.

MP particles were extracted via density separation and identified on Nile red-stained filters under visible and UV light. Polymer composition was determined for approximately 10% of the suspected MP particles using Fourier Transform Infrared (FTIR) spectroscopy. We observed the predominance of fibers (66-89% of total particles) over fragments (11-34%), with polyethylene terephthalate (PET) as the most common polymer, followed by semisynthetic cellulosic fibers. No MP particles were detected in sediments before 1950. An accelerated increase in MP burial rates was observed from the mid-20th century, likely linked to population growth and the expansion of plastic use. The highest MP levels were observed in the lagoon’s innermost areas, where the water residence time is highest. This rising contamination poses risks to subsistence fishing and shrimp aquaculture, emphasizing the need for strengthened waste management and pollution control strategies in rapidly industrializing and urbanizing areas to mitigate adverse impacts on ecosystems and human communities reliant on them. Harmonizing monitoring and assessment protocols for plastic pollution across the Latin American and Caribbean region is essential for producing comparable data that can guide regional policies and inform global efforts to mitigate the escalating impacts of plastic pollution on marine and coastal ecosystems.