Microplastic ingestion by a herring Opisthonema sp. in the Pacific coast of Costa Rica

Abstract

Current knowledge of the presence of microplastics (MP) in marine species in tropical areas is still limited. The presence of MP was examined in the gastrointestinal content of 30 filter feeders of the herring Opisthonema complex (Clupeiformes: Clupeidae) from the Central Pacific of Costa Rica. MP were detected in 100% of the individuals with an average of 36.7 pieces per fish, of which 79.5% were fibers and 20.5% particles. No direct association between biometric variables or sex and the amount of microplastic was found. Different physicochemical analyses were carried out to determine the composition and characteristics of the microplastics. Most of the fibers were classified as polypropylene. Remarkably, some plastic particles turned out to be composed exclusively of minerals. This study demonstrates the high presence of MP in planktivorous fishes of the Pacific coast of Central America. Also, we propose the Opisthonema complex as a model for biomonitoring microplastic pollution in the Tropical Eastern Pacific due to its wide distribution, biometric homogeneity of the schools, non-selective feeding type, and its crucial position in the marine food webs.