Comparing microplastics ingested by the bogue Boops boops (Teleostei: Sparidae) to those available in its feeding areas: A case study on the Portuguese west coast

Abstract

Understanding the exposure of wild marine fish to microplastics (MPs) has been frequently assessed through the quantification and characterization of MPs found in stomachal contents. However, whether such particles mirror the MPs available in the environment or suggest a selectivity ability in the species, it has been scarcely analyzed. Here, in addition to investigating temporal patterns in the abundance and diversity of MPs ingested by Boops boops (Linnaeus, 1758) caught in coastal waters between Setúbal and Sesimbra (Portugal), we also aimed at comparing them with the patterns of MPs occurring locally, namely where the bogue feeds: at both surface water and seabed sediments. A total of 200 fish, 50 per month, were supplied at the local fish first sale concurrently with the water and sediments sampling (from October 2018 to January 2019). Fibers accounted for 93% of all MPs ingested and were also the main type of MPs extracted from sediments. Both food intake (inferred by fish gastrointestinal tract) and abundance of MPs per fish (1.80 ± 1.26; mean ± SD, n = 102) significantly decreased during the 4 month-period analyzed. Such decreasing tendency is potentially related to this species reproduction season. Despite the distinct fluctuations observed in the abundance of MPs found in both feeding areas of the bogue, it was possible to detect similarities between fish and sediments regarding the predominance of fibers, namely those belonging to the smaller size class. Yet, the prevailing colors differed, suggesting a selection capability of the bogue. Further studies taking place in spring/summer months (out of the reproduction season) are thus needed to clarify how MPs ingestion will vary in this species and consequently interfere with its ability to mirror the MP pollution patterns in this coastal region.