Microplastics ingestion by the exotic fish Gambusia holbrooki in two Mediterranean coastal lagoons

Abstract

Gambusia holbrooki is a fish of North American origin introduced in the early 20th century in wetlands of the Iberian Peninsula for the biological control of mosquitoes. This fish feeds mainly on invertebrates, but they are also susceptible to ingesting and accumulating microplastic residues similar in size to some of their usual prey. In this study, we analyzed the contents of the gastrointestinal tract of adult individuals of this species from two restored coastal lagoons, to characterize the ingestion of microplastics. 156 specimens of Gambusia holbrooki were analyzed: 92 females and 64 males. Females had a greater weight and length than males. 44% of the fish presented some microplastic residue (fibers or fragments) in their gastrointestinal contents. Most of the microplastics (48%) ranged between 100 and 400 µm. Blue fibers and brown fragments were the most common. The average number of microplastics per individual was slightly higher in males than in females, in spring samples than in summer ones, and in lagoon G02 compared to L04, although only significant differences were found between the lagoons. In addition, individuals with lower weight presented a greater amount of microplastics. In this sense, the presence of microplastics in the gastrointestinal contents of fish can be an indicator of the increase in plastic residues in Mediterranean coastal ecosystems, with the potential to alter the trophic dynamics of aquatic organisms.