Seasonal variation in plastic litter pollution in mangroves from two remote tropical estuaries of the Colombian Pacific.

Mangroves in estuaries are highly vulnerable to the impacts of plastic litter pollution, because their location at river mouths and the high capacity of mangrove trees to trap plastic items. Here, we present new results on the abundance and characteristics of plastic litter during high and low rainfall seasons in mangrove waters and sediments of the Saija and Timbiqui River estuaries in the Colombian Pacific. In both estuaries, microplastics were the most common size (50-100 %), followed by mesoplastics (13-42 %) and macroplastics (0-8 %). Total abundances of plastic litter were higher during the high rainfall season (0.17-0.53 items/m in surface waters and 764-832 items/m in sediments), with a moderately positive relationship between plastic abundances recorded in both environmental matrices. The most common microplastics were foams and fragments. Continuous research and monitoring are required for a better understanding and management of these ecosystems and their threats.