Evaluation of anthropogenic particles in Arbacia lixula sea urchins and their surrounding environments: seawater and coastal sediments

The widespread presence of anthropogenic particles (i.e. microplastics) in marine coastal environments poses a significant threat to ecosystems and marine life health. This study assesses the distribution of these particles in 30 specimens of Arbacia lixula sea urchin (in their gastrointestinal tracts and gonads, separately) as well as its surrounding environments, including 10 coastal sediments and 10 seawater samples of two locations of La Palma Island (Puerto Espíndola and Los Cancajos) to explore potential relationships between particle distribution in these compartments. Sampling was developed in December 2021 and 2022. Results showed consistent patterns in particle abundance, shape, colour, size, and composition across both years. Sea urchins contained an average of 3.5 ± 5.4 to 0.8 ± 1.0 items per individual, seawater 14.0 ± 5.5 to 2.6 ± 2.4 items per litre and coastal sediments 0.9 ± 0.5 to 0.3 ± 0.1 items per gram of dry sediment. Fibres were the predominant particle shape (96.4 %), followed by fragments (3.3 %) and lines (0.3 %), with most particles being colourless/translucent (66.5 %) and blue (19.3 %). Particles sized between 500 and 1000 µm were most common (31.4 %). µFTIR analysis indicated that particles were mainly cellulosic -natural and semisynthetic- (74.9 %), with microplastics also present, including polyester (12.6 %) and PEVA (poly(ethylene-co-vinyl acetate)) (1.4 %). The consistency of results over two years highlights the persistence of this type of pollution and its potential long-term impact on coastal marine ecosystems. • Arbacia lixula shows potential as a bioindicator of anthropogenic particles in Atlantic waters. • Cellulosic fibres were the most abundant polymer type found. • Consistent particle patterns observed across two sampling years. • Arbacia lixula accumulated particles in gut and gonads.