An affordable method for monitoring plastic fibre ingestion in Nephrops norvegicus (Linnaeus, 1758) and implementation on wide temporal and geographical scale comparisons

Although the ingestion of plastics has been reported in a wide variety of organisms, there remains a lack of knowledge regarding the extent of spatial and temporal gradients and no consensus concerning the definition of monitor species for benthic marine environments. The present study aims at demonstrating the correlation between the presence of tangled balls of fibres and high levels of total plastic fibre ingestion in Nephrops norvegicus to assess the potential use of the prevalence of tangled balls as indicators of fibre pollution. To do so, the presence of plastics in stomach contents from several European populations of N. norvegicus is characterized in detail, including size distribution and polymer composition, and then its correlation with the prevalence of balls tested. Our results demonstrate that the prevalence of balls (>20%) is significantly correlated to higher levels of plastic ingestion, regardless of polymer composition and size distribution of ingested fibres. Plastic fibre ingestion levels across wide temporal and geographical scales are assessed using only the prevalence of balls, highlighting areas of increased fibre ingestion (e.g., the Gulf of Cadiz, N Barcelona) and areas of potentially lower fibre pollution (e.g., the Ebro Delta, the NW Iberian margin). Moreover, the relationship between the prevalence of balls and diet composition is analysed to discard a potential relationship with geographical differences in diet habits. Finally, we discuss the benefits and drawbacks of the use of the prevalence of tangled balls of fibres as an affordable, cost-effective and easy to implement indicator of fibre pollution for monitoring purposes in this species.