Study on the consumption of microplastics by fishes in a floodplain lake of the Curiaú River (Macapá – Amapá, Brazil)

Abstract Plastics are used in almost every aspect of modern life from construction and electronics to clothing and food packaging. Freshwater ecosystems are the ultimate destination for many pollutants including plastic particles smaller than 5 mm, so-called microplastics. When available in the aquatic environment, these particles are actively or passively consumed by fishes. Studies on the natural diet of fishes can highlight and elucidate the impacts of this pollutant on aquatic ecosystems. The stomachs, intestines and gills from 122 fishes collected from Curiaú River Resort during the dry and rainy seasons, were analyzed by chemical digestion with KOH to verify the presence of microplastics. The fishes were categorized by taxa (14 species), feeding guild (herbivore, carnivore, piscivore, omnivore) and collection period (dry vs. rainy). We found a total of 732 microplastics, all classified as fibers, in 96% of the fishes examined. The predominant colors of the fibers were blue (59%) and black (33%). The highest consumption of microplastics occurred during the rainy season. Among the six most abundant species sampled, microplastics were most common in Geophagus sp., a fish that forages by sifting substrates dominated by sand. We also found differences between feeding guilds with carnivores scoring highest in the consumption of microplastics. We found no association between fish size and weight and the quantity of microplastics consumed. This study provides valuable baseline data on the ingestion of microplastics by fishes in the Curiaú Resort, and new insights into microplastic consumption by freshwater fishes. Our results are compared to similar studies of fishes in aquatic environments around the world.