Assessment of microplastic impacts on whitemouth croaker (Micropogonias furnieri) and ecosystem services in Guanabara Bay, Brazil

Microplastics (MPs) are an emerging contaminant potentially impacting organisms and ecosystem functioning. Despite the high abundance of MPs in Guanabara Bay, studies on MP ingestion are lacking. Analyses of 272 stomachs of Micropogonias furnieri, a key estuarine species, revealed that ~ 50% of fish ingested MPs, with an average of 3.7 MPs per individual. Polyester and polyethylene fibers were the dominant types of MPs found in both stomachs and bay sediments. Comparisons of the MP types in the fish stomachs and those previously described in the sediment showed that M. furnieri ingested MPs according to the availability but also exhibited selectivity for some rare MPs (i.e., blue and red fibers). Analyses of M. furnieri stomachs indicated that higher MP ingestion was associated with a larger quantity of food ingested, low digested food items, larger fish, dry season, and two bay locations, suggesting that this species serves as a valuable indicator of feeding area quality. MPs occurred only in stomachs with food, and estimates of egestion rates showed short residence time of food and MPs, indicating no MP accumulation in fish stomachs. The results also revealed that juveniles had more MPs in their stomachs per gram of body weight. MPs did not appear to impact M. furnieri feeding, but the effects of adsorbed chemicals on fish health require further evaluation. As M. furnieri ingests more food, it becomes more exposed to the effects of MPs, highlighting the MP threat to the ecosystem services provided by the bay, such as fish feeding areas.