Intake of microplastics by fishes in a floodplain lake of the Curiaú River (Macapá, Amapá, Brazil)

Plastics are used in almost every aspect of modern life, ranging from construction and electronics to clothing and food packaging. Freshwater ecosystems are the ultimate destination for many pollutants, including plastic particles with diameter < 5 mm, commonly referred to as microplastics. When present in the aquatic environment, fishes actively or passively consume these microplastic particles. Studies on the natural diet of fishes can highlight and elucidate the impacts of this pollutant on aquatic ecosystems. In the study reported here, the stomachs, intestines and gills from 122 fishes (14 species) collected from the 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 trophic 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 fish species sampled, microplastics were most common in the cichlid Geophagus (eartheaters). We also found differences between trophic guilds, with carnivores scoring highest in terms of the consumption of microplastics. We found no association between fish size and weight and the quantity of microplastic particles consumed. This study provides valuable baseline data on the ingestion of microplastics by fishes in the Curiaú Resort, as well as new insights into the consumption of microplastic particles by freshwater fishes. We also compared our results to those from similar studies of fishes in aquatic environments around the world.