Microplastics are widely recognised as contaminants of emerging concern. In the marine environment, seabed sediments have been identified as a major sink with a high potential to accumulate them [1]. Among microplastic forms, microfibres appear among the most frequently reported in the environmental compartment [2]. The aim of this study was to quantify plastic microfibres in marine sediments of La Palma island (Canary Islands, Spain). Sediment samples were collected during July 2020 at four sampling locations with uniform sandy seabed and a water depth between 5 and 10 m. At each sampling point, three samples were taken parallel to the coast and separated 10 m from each other. Stainless steel cores, 10 cm depth, were used for sample collection, and microfibres content was evaluated at the laboratory every 2.5 cm (total samples = 48). First, each sediment sample (10 g) was digested with 33 % H2O2 in order to remove the organic matter. After that, several sequential flotations developed by the addition of a saturated solution of sodium chloride were carried out, and each supernatant was filtered through a 50 µm stainless steel filter. Filters were covered to prevent airborne contamination and stored for subsequent visual sorting using a binocular light microscope. Results revealed that all assessed sediment samples contained microfibers. Isolated microfibres were mainly translucent and, to a lesser extent, coloured (e.g. blue, red and black). This study has confirmed the widespread distribution of microplastics in sediments from an oceanic island, providing the first report on microplastics in marine sediments of the Canary Islands. References 1 T. Martellini, C. Guerranti, C. Scopetani, A. Ugolini, D. Chelazzi and A. Cincinelli, TrAC Trends Anal. Chem., 2018, 109, 173–179. 2 S. L. Wright, R. C. Thompson and T. S. Galloway, Environ. Pollut., 2013, 178, 483–492.