Researchers from the University of Vigo, the University of Santiago de Compostela and the Spanish Institute of Oceanography in Vigo have carried out a study on the transport of plastics of different sizes that enter the Gulf of Biscay in order to analyse their fate within this area. The results obtained indicate that this gulf constitutes a trapping zone for the plastics that reach it.
The work was recently published in the Journal of Sea Research in an article entitled The Bay of Biscay as a trapping zone for exogenous plastics of different sizes and signed by Laura Rodríguez, Moncho Gómez Gesteira and José Luis Gómez Gesteira, of the Environmental Physics Laboratory (Ephyslab) group, of the Marine Research Center of the University of Vigo; Xurxo Costoya, from the Cross-disciplinary Research in Environmental Technologies Institute (Cretus), from the USC, and Jesús Gago, from the Oceanographic Center of Vigo, from the IEO.
As the authors of the work explain, “it is estimated that around 10% of the plastics produced will end up in the ocean, representing approximately 70% of marine litter”. The dispersion and accumulation of these plastics in certain regions of the world, they add, depends in part on their buoyancy, which varies according to their size. In this global context, they detail, the Gulf of Biscay is considered a medium-level region in terms of plastic pollution.
Microplastics and larger plastics
In the study, the researchers used a Lagrangian model to simulate the trajectories followed by plastics with virtual particles. As they explain, “although it was seen that the general pattern followed by plastics depends mainly on ocean currents, the wind can modulate it especially in the case of larger plastics”. For this reason, in order to evaluate the fate of plastics that enter the Bay of Biscay through the strait north of Cape Ortegal, this work used “the speeds of sea currents and different drag coefficients to take into account their diversity of sizes and, therefore, their exposure to the effect of the wind”.
As a result of the work carried out, those responsible indicate, “it was detected that the plastics that enter the Bay of Biscay rarely leave this area, which makes it a region of entrapment”. Thus, they point out, only a small percentage of plastics, between 4 and 15%, dispersed towards the Atlantic coast of the Iberian Peninsula or exceeded French Brittany. The entrapment of plastics in the Bay of Biscay, they indicate, “had a particularly noticeable result in larger plastics (>5 mm) strongly affected by the wind that pushes them towards land”. In fact, the researchers detail, “this type of plastics tend to accumulate in a narrow strip along the coast (with a probability of around 90%), which favors their accumulation on the coast (with a probability of 60%). On the contrary, they add, microplastics (< 5mm) showed a great tendency to disperse freely towards the ocean, being able to reach any location within the gulf studied, “which is worrying because their small size makes sampling and collection tasks difficult.”
A actividade investigadora do grupo Ephyslab conta co apoio da Xunta de Galicia e a Unión Europea, a través do cofinanciamento do CIM no marco do Programa Operativo FEDER/FSE Galicia 2014-2020.
Source: DUVI
