Surface layer microplastic pollution in four bays of the central Mexican Pacific

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 Bahia 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.

Automated summary

The study on the impact of sea surface microplastic concentration in four tropical bays in central Mexican Pacific found that there was no significant difference in fiber concentration among bays and seasons, while fragment concentration was significantly higher in Manzanillo and Santiago. Raman spectroscopy data revealed different polymer types, and non-metric multidimensional scaling showed distinct microplastic distribution in different bays.