Microplastic pollution in sublittoral coastal sediments of a North Atlantic island: The case of La Palma (Canary Islands, Spain)

Cristina Villanova-Solano,Francisco J Díaz-Peña,Cintia Hernández-Sánchez,Javier González-Sálamo,Miguel González-Pleiter,Daura Vega-Moreno,Francisca Fernández-Piñas,Eugenio Fraile-Nuez,Francisco Machín,Javier Hernández-Borges

doi:10.1016/j.chemosphere.2021.132530

Abstract

In this work, the microplastic content of sediments collected in July 2020 between 5 and 7 m depth was studied in four locations of La Palma island (Canary Islands, Spain). At each sampling location, three samples were taken parallel to the shoreline. The microplastic content in each sampling corer was studied every 2.5 cm depth after digestion with a H2O2 solution followed by flotation in a saturated NaCl solution. Visualization of the final filtrates under a stereomicroscope revealed that all the sediment samples evaluated contained mostly microfibers (98.3%) which were mainly white/colorless (86.0%) and blue (9.8%), with an average length of 2423 ± 2235 (SD) mm and an average concentration of 2682 ± 827 items per kg of dry weight, being the total number of items found 1,019. Fourier Transform Infrared microscopy analysis of 13.9% (n = 139) of the microfibers also showed that they were mainly cellulosic (81.3%). No significant differences were found between the depths of the sediment. However, significant differences were found between the number of fibers from the sampling sites at the east and west of the island. Such variability could be driven by the winds and ocean mesoscale dynamics in the area. This study confirms the wide distribution of microfibers in sediments from an oceanic island like La Palma, providing their first report in marine sediments of the Canary Islands.

Highlights

Plastic pollution is nowadays one of the biggest problems that humans should face in the forthcoming years
Concerning the first case, a good number of studies have shown that thousands of microfibers are released during laundering (Gaylarde et al, 2021) and that their release through wastewater treatment plants or sludges constitutes an important source of their presence in the environment, many studies clearly indicate that an extremely high percentage of microplastics is removed (Bayo et al, 2020; Salvador Cesa et al, 2017)
Subtidal coastal sediments were collected in triplicate at four sampling locations of La Palma island in July 2020, in order to undertake a study of the potential contamination by microplastics of seabed sediments since, as indicated, no previous studies like this one have already been developed in this region

Summary

Introduction

Plastic pollution is nowadays one of the biggest problems that humans should face in the forthcoming years. In Spain, to the best of our knowledge, only the works by Alomar et al (2016), who analyzed sediments down to 10 m depth in the Balearic Islands (Spain), Filgueira et al, who studied sediments of 43–154 m depth along the Spanish Mediterranean continental shelf (Filgueiras et al, 2019), as well as that of Carretero et al (2021), who studied the microplastic content of sed iments from Rías Baixas and Mino river shelf collected down to 17–375 m, have been published Despite these few reports, it is highly desirable to increase knowledge in this specific area in order to deter mine the current health of the seas and to take suitable and effective actions to decrease the presence and impact of microplastics in them

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Conclusion