The incidence of plastic ingestion in seabirds from the Bay of Biscay (northeastern Atlantic).

Supervisors: Maite Louzao, Javier Franco (AZTI).
The Marine Strategy Framework Directive (MSFD) requires European state members to implement strategies to achieve “Good Environmental Status” (GES) in European Seas by 2020. Descriptor 10 of the MSFD states that “Properties and quantities of marine litter do not cause harm to the coastal and marine environment”. Following the guidelines set by the MSFD, the OSPAR Commission set an Ecological Quality Objective (EcoQO) to monitor marine plastic trends in the North Sea by using the Northern Fulmar (Fulmarus glacialis) as a biomonitoring species to plastic ingestion. In the Bay of Biscay however, the Northern Fulmar is very scarce and few carcasses can be recovered from beached bird surveys. Furthermore, little is known about the marine plastic litter abundance in surface waters of this region. Hence, this study aims to obtain the first data on the ingestion of plastics in seabirds occurring in the Bay of Biscay using several research methods and to assess their suitability as biomonitors of plastic pollution. Analyses of the stomach content of deceased birds were carried out in 152 individuals of 14 species. Carcasses were obtained from two different zones of the Bay of Biscay: a northern area located on the western coast of France in the Nouvelle-Aquitaine region and a Southern area located along the Atlantic coast of the Iberian Peninsula. In addition, 68 pellets were collected from several colonies of European Shag (Gulosus aristotelis) located in Bizkaia and Cantabria to assess the suitability of this methodology as a complementary analysis to stomach content data. Plastics were found in 25 individuals (16.5% of the total) of eight species (57.1% of species). Frequency of occurrence (FO) of plastics varied between 0% and 100%, with the highest FO found in Northern Fulmar, Balearic Shearwater, and Great Shearwater. From a total of 110 pieces of plastic ingested by seabirds, the majority of them were microplastics (71%). The frequency of occurrence of plastics in seabird pellets was lower than in stomachs of deceased birds (10%), although microplastics were also the most abundant plastic category. The subsequent Mann-Whitney-U statistical analysis determined that only Procellariiformes (Northern Fulmars and shearwaters) were statistically significant with the rest of seabird families regarding plastic ingestion and that based on the analysis of GLMM, the probability of ingesting plastics was negatively correlated with the body condition. Considering several criteria to assess their suitability as biomonitors of plastic pollution (frequency of occurrence of plastic ingestion, species abundances and stranding occurrence in the Bay of Biscay), the Common Murre and the Atlantic Puffin seem the most promising candidates. Additionally, seabird pellets analysis combined with stomach content analysis of deceased birds provides a multi-dimensional record of plastic prevalence in marine birds. This study provides the first data on plastic ingestion in seabirds of the Bay of Biscay.