Monitoring annual plastic pollution on beaches of La Gomera Islands (Canary Islands, Spain) and its relationship with environmental variables.
Supervisors: Javier Hernandez-Borges, Cintia Hernandez-Sanchez (U La Laguna)
Plastic pollution has been extensively studied. Its presence in different environmental compartments has been demonstrated as well as its impacts on the marine environment and in marine organisms. Beaches are an important compartment where plastic can be accumulated or also can be a source of marine plastic debris. In the present study, micro, meso and macroplastic debris in five beaches of La Gomera Island (Canary Islands, Spain) have been studied from Summer 2020 to spring 2021 (five replicates for each sampling at each season and each beach), finding a total of 1780 plastic items with a total weight of 46.43 g and a concentration of 71.2 ± 173.1 items/m2 (1.86 ± 7.13 g/m2), being microplastics the main size fraction (51.8 ± 139.4 items/m2), followed by mesoplastics (14.4 ± 44.9 items/m2) and macroplastics (4.9 ± 23.5 items/m2). The majority of the plastic in terms of items was found during fall at Vueltas beach, while in terms of weight it was during winter at San Sebastián beach. Fragments were the main shapes found (63,0 %), and the main colors were light brown, light yellow, white and transparent (64.9 %). The infrared spectroscopy analysis of the microplastic fraction showed that PP and PE are the main types of polymers.

La Gomera presented lower plastic pollution compared with other Canary Islands’ beaches, however, in the present study, plastic debris was observed in all beaches and seasons of the year of study. The analysis of environmental variables and ocean currents were carryout with the aim to identify its influence on the spatial and temporal variation of the plastic debris. It was found that sea surface currents could be influencing microplastic accumulation at Vueltas beach due to its south-east orientation, it has open access to the south-west currents. In the case of San Sebastián, the main concentration was found during winter, which could have been influenced by the rainy and stormy season additionally to its characteristic of ravine discharge that flows directly to the beach, however, further study is necessary to confirm this hypothesis. The continuous growth of plastic production continues to increase the prevalence of plastic debris in the marine environment, being an increasingly evident threat to the Canary Islands, since they are highly exposed to pollution brought by currents from distant and regional sources of which they have no control, in addition to the plastic debris that is locally generated at each island.