Methods to characterize microplastics: case study on freshwater fishes from a tropical lagoon in Colombia

Aquatic ecosystems face multiple anthropogenic pressures, and recently plastic pollution is one of the main problems. The Luruaco lagoon receives discharges from streams with high levels of microplastics (MPs) from urban areas that impact the resident ichthyofauna. We studied the prevalence, abundance and physical and chemical characteristics of MPs in fishes in the Luruaco Lagoon, Colombia. Four samplings were carried out where fish were captured with trawl nets. Each individual was assessed for total weight, total and standard length, and then a uroventral cut was made to extract stomach and intestine (GIT). Each structure was weighed, measured, and deposited in glass jars with filtered KOH solution. The abundance of MPs and frequency of occurrence were assessed. A principal component analysis (PCA) was used to describe the variation of the species dataset (%FO, proportion of MPs and their diet). Seven species were recorded and 271 individuals examined: Microplastics were identified in all species, and 1157 particles were found in their GIT, with a prevalence of 87.5% of MPs. Mugil liza and Andinoacara latifrons had a high proportion of MPs. The highest %FO was found in cichlid species. Four typologies and 13 colors of MPs were analyzed; fibers and color blue were predominant. A direct relationship was observed between the type of diet and the proportion and %FO of MPs.