Kozak, Eva R., Franco-Gordo, Carmen, Mendoza-Pérez, Jorge, Sánchez-Nuño, Nancy, Martínez-Sánchez, Xenia A., Melo-Agustín, Paola, Pelayo-Martínez, Gloria, and Gómez-Gutiérrez, Jaime
Surface microplastics were sampled monthly in four tropical bays (Manzanillo, Santiago, Navidad and Cuastecomates) of the central Mexican Pacific during March 2017 to February 2018. Microplastic concentrations ranged between 0.01 and 1.05 particles/m2 with a median per bay ranging between 0.26 and 0.40 particles/m2. Raman spectroscopy registered polypropylene (40%), polyethylene (40%) and polyester (20%) polymers. Fibers dominated all samples, except for Manzanillo where fragments numerically dominated during the rainy season (Jun-Oct). Fiber concentration was not significantly different among bays or seasons, likely associated with continuous wastewater discharge. Fragment concentrations were significantly higher in Bahía Manzanillo and Santiago than the other two bays. Non-metric multidimensional scaling showed distinct distribution of Manzanillo samples (which has important port activities) as compared to Santiago, Navidad, Cuastecomates (where tourism economic activities predominate). This first direct comparison of sea surface microplastic concentration among four bays in Mexico provides a baseline to study impacts on marine zooplankton in this tropical ecosystem. • Microplastic concentration was compared in four tropical bays of the central Mexican Pacific during an annual cycle. • Microplastic concentrations ranged between 0.01-1.05 particles/m2. • Bahía Manzanillo showed distinct fragment variability than bays with touristic/urban activities, but without ports. • Wastewater effluents are an environmental problem in the four bays and action must be taken. • This study is a baseline for future work about the impact of microplastics on marine animals in the Eastern Tropical Pacific. [ABSTRACT FROM AUTHOR]