Coupling Gastro-Intestinal Tract Analysis With an Airborne Contamination Control Method to Estimate Litter Ingestion in Demersal Elasmobranchs

Abstract

This study aims to assess the litter ingestion in some demersal elasmobranchs, combining a classical gastro-intestinal tract (GIT) analysis with a procedure methodology to reduce airborne fibers contamination. In order to prevent the overestimation of litter ingestion, we applied severe mitigation measures to avoid airborne contamination during the analyses, integrating a new approach for the correction of estimates of fibers abundance using control procedure. In this study, we assessed the anthropogenic litter ingestion in four elasmobranch species from the southern Tyrrhenian Sea: Scyliorhinus canicula (n = 27), Etmopterus spinax (n = 16), Galeus melastomus (n = 12), and Raja clavata (n = 6). The GIT of each specimen was analyzed by visual sorting and the polymers identified by Fourier transform infrared spectroscopy technique. Overall, 19 litter particles were found in the GIT of 13 demersal elasmobranchs (%O = 21) and for the first time, evidence of litter ingestion by R. clavata in Mediterranean waters was also reported. In G. melastomus and R. clavata all anthropogenic particles were plastics, whereas in S. canicula other litter categories were also found. No litter ingestion was instead observed in E. spinax. More than 50% of litter particles belonged to microlitter category (<5 mm). Polyamide was the only polymer typology found in all examined species. We described the procedures to control the airborne contamination applied at each step of laboratory analysis and, thanks to the application of our control method, it was possible to exclude the 95% of fibers found in samples from the assessment. Moreover, we compared fibers abundances observed in samples and controls. This study, combining an approach for minimizing the bias associated to airborne fiber contamination, provided a reliable assessment of marine litter ingestion in demersal elasmobranchs.

Anthropogenic pollutants in Nephrops norvegicus (Linnaeus, 1758) from the NW Mediterranean Sea: Uptake assessment and potential impact on health

“…In both (Sardinian coast and the Adriatic Sea) studies, samples were digested, which may allow identifying particles of a smaller size but may have destroyed fibres (Athey and Erdle, 2021), while Cau et al (2019) purposely excluded over 2000 textile fibres from their results because of a potential airborne uncontrolled origin. The overestimation of fibres due to contamination during processing has been a subject of debate in plastic ingestion studies (Foekema et al, 2013;Pedà et al, 2020). Although the contribution of airborne fibres cannot be fully ruled out in our study, the strict quality control procedures implemented together with the high contribution of tangled balls of fibres, which are certainly not a result of sample contamination, support the dominance of fibres in N. norvegicus.…”

Diet and Plastic Ingestion in the Blackmouth Catshark Galeus melastomus, Rafinesque 1810, in Italian Waters

“…One of the main challenges faced when analysing plastic fibres derives from specimen contamination by exogenous agents, such as airborne fibres. To avoid false negatives, controlled measures have been put in place, in accordance with other studies such as Pedà et al [ 45 ]. Each operator was wearing a lab cotton coat, Petri dishes were covered with carefully washed caps, windows were closed, ventilation systems shut off, and the steel instrumentation was thoroughly washed with distilled water before each dissection.…”

“…According to Eriksen et al [ 64 ] and Valente et al [ 48 ], the shape (fibres, fragments, film, or sphere) and the colour (black, blue, green, grey, orange, red, white, or yellow) were noted. All plastic remains were also measured using graph paper and divided into micro-, meso-, and macroplastics following the categories of the Marine Strategy Framework Directive [ 45 , 65 , 66 , 67 , 68 , 69 , 70 ], in which the upper boundary of the microplastics was 5 mm and the upper size of the mesoplastics was 25 mm. Plastics < 1 mm were considered microplastics, and macroplastics did not have an upper boundary (>25 mm).…”

“…Among sharks, analyses on blackmouth catsharks were conducted in the Balearic Islands, highlighting the presence of plastics [ 43 ]. In the last decade, a growing body of evidence has reported the presence of plastics in the stomach contents of G. melastomus in the Mediterranean Sea [ 44 , 45 , 46 , 47 , 48 ].…”

Anthropogenic microparticles in the emerald rockcod Trematomus bernacchii (Nototheniidae) from the Antarctic

“…The beakers were covered with aluminium foil between each step to prevent airborne contamination. Procedural blanks were also run concurrently to avoid fibers overestimation, moist filters in Petri dishes were put under the microbiological hood and exposed to the laboratory air near the stereomicroscope 64 . Procedural blanks without tissue were also run concurrently with samples.…”