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Abstract The presence of marine litter is a complex, yet persistent, threat to the health and biodiversity of the marine environment, and plastic is the most abundant, and ubiquitous type of marine litter. To monitor the level of plastic waste in an area, and the prospect of it entering the food chain, bioindicator species are used extensively throughout Northern European Seas, however due to their distribution ranges many are not applicable to the Mediterranean Sea. Guidance published for the Marine Strategy Framework Directive suggests that the contents of fish stomachs may be analyzed to determine trends of marine plastic ingestion. In order to equate transnational trends in marine plastic ingestion, the use of standardized fish species that widely occur throughout the basin is favoured, however for the Mediterranean Sea, specific species are not listed. Here we propose a methodology to assess how effective Mediterranean fish species, that are known to have ingested marine plastic, are as bioindicators. A new Bioindicator Index (BI) was established by incorporating several parameters considered important for bioindicators. These parameters included species distribution throughout the Mediterranean basin, several life history traits, the commercial value of each species, and the occurrence of marine litter in their gut contents. By collecting existing data for Mediterranean fish, ranked scores were assigned to each trait and an average value (BI value) was calculated for each species. Based on their habitat preferences, Engraulis encrasicolus (pelagic), Boops boops (benthopelagic), three species of Myctophidae (Hygophum benoiti , Myctophum punctatum and Electrona risso) (mesopelagic), Mullus barbatus barbartus (demersal) and Chelidonichthys lucerna (benthic), were identified as currently, the most suitable fish for monitoring the ingestion of marine plastics throughout the Mediterranean basin. The use of standardized indicator species will ensure coherence in the reporting of marine litter ingestion trends throughout the Mediterranean Sea. Graphical abstract Image 1 Highlights • An index describes suitable marine plastic fish bioindicators in the Mediterranean. • European anchovy is well suited to monitor plastic trends in pelagic environments. • Boops boops appears the most adept plastic bioindicator for benthopelagic habitats. • For marine demersal habitats, Mullus barbatus barbatus is a suitable bioindicator. • The work contributes to standardization of Mediterranean monitoring protocols. Using a novel index, seven species of fish were identified as the most suitable to monitor marine plastic ingestion trends in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are recognized as an increasing threat to the marine environment, but little is known about their effects on benthic organisms, including sea urchins, when ingested. For this purpose, wild sea urchins (P. lividus) and seafloor sediment samples were investigated across three coastal areas of Zakynthos Island (Ionian Sea), each exposed to different anthropogenic pressures, revealing a consistent pattern in MP abundance, shape, and color. Biomarkers related to oxidative stress, neurotoxicity, and genotoxicity showed no significant effects of MP ingestion in the sea urchins, except for a positive correlation between GST activity and ingested MPs, suggesting a possible activation of their detoxification system in response to MP ingestion. While MP concentrations in sea urchins and sediments were within the low range reported in the global literature, it remains crucial to conduct further investigations in areas with MP pollution approaching predicted levels to fully comprehend the potential effects of MP pollution on marine organisms. [Display omitted] • Low microplastic abundance in sediments and sea urchins in Zakynthos Island • Blue fibers dominate in both sediments and sea urchins. • Microplastic ingestion did not exhibit significant effect on sea urchins. • Positive correlation between GST activity and ingested MPs • FTIR analysis revealed majorly PP, PE, PVA in sediments and PP in sea urchins. [ABSTRACT FROM AUTHOR]

Abstract Microplastic ingestion by marine organisms presents an emerging threat to marine ecosystems; microplastics in different marine species are currently reported worldwide. This study aims to assess microplastic ingestion in four, highly commercial, marine species from Greek waters in the Northern Ionian Sea (Mediterranean Sea). Microplastics were found in mussels (Mytilus galloprovincialis) and all three fish species (Sardina pilchardus , Pagellus erythrinus , Mullus barbatus) examined. The frequency of occurrence of ingested microplastics was 46.25% in mussels, while among fish species, S. pilchardus showed the highest frequency of microplastic ingestion (47.2%). Microplastic abundance ranged from 1.7–2 items/individual in mussels and from 1.5–1.9 items/individual in fish. The majority of ingested microplastics were fragments, while their color and size varied. Fourier Transform Infrared Spectroscopy (FT-IR) indicated polyethylene as the most common polymer type in mussels and fish. Results can be used to set baseline levels for the assessment of microplastic pollution in the Ionian Sea. Highlights • Microplastics were detected in commercial species from the Northern Ionian Sea. • Sardines and mussels presented the highest frequency of occurrence of ingested microplastics. • Polyethylene is the most common polymer detected in the species investigated. [ABSTRACT FROM AUTHOR]

This study assesses microplastic ingestion in Boops boops at different geographical areas in the Mediterranean Sea. A total of 884 fish were caught at 20 coastal sites in Spain, France, Italy and Greece and analyzed using a common methodological protocol. Microplastics were found in 46.8% of the sampled fish, with an average number of items per individual of 1.17 ± 0.07. Filaments were the predominant shape type, while polyethylene and polypropylene were indicated by FTIR as the most common polymer types of ingested microplastics. The frequency of occurrence, as well as the abundance and proportion of types (size, shape, color and polymer) of ingested microplastics, varied among geographical areas. The spatial heterogeneity of the abundance of ingested microplastics was mainly related to the degree of coastal anthropogenic pressure at the sampling sites. Our findings further support the suitability of B. boops as bioindicator of microplastic pollution in the Mediterranean Sea. • High incidence of microplastic ingestion in Boops boops from the Mediterranean Sea • Ingested microplastics were predominantly filaments. • Polyethylene and polypropylene were the most common polymers detected. • Frequency of occurrence, abundance and types of microplastics varied spatially. • Microplastic abundance related to coastal anthropogenic pressure [ABSTRACT FROM AUTHOR]

Plastic debris has become a major threat to the marine environment and wildlife. Sea turtles are particularly vulnerable, and are known to ingest plastic debris globally; however, information from Greek waters is still absent. In this study, 36 stranded dead loggerhead turtles (Caretta caretta) were collected from the Greek coastline area, and their gastrointestinal content was analysed for ingested plastic debris. Twenty-six individuals (72%) were found to have ingested plastic, with an average of 7.94 ± 3.85 (SE) plastic items per turtle. In total, 286 plastic items were counted and categorised by size, shape, colour, and polymer type. Fourier Transform Infrared Spectrometry revealed that polypropylene and polyethylene were the dominant polymer plastic types found. Results indicated a variation in plastic ingestion amongst life stages of the loggerhead specimens. This study provides evidence of plastic ingestion by loggerhead turtles in Greek waters. Image 1 • Plastic ingestion by sea turtles investigated for the first time in Greek waters. • 72% of the loggerheads were found to have ingested plastics. • Plastic ingestion varies along sea turtles' life stages. • Higher levels of sinking polymers (PET, Nylon) in adult specimens. High occurrence (72%) of plastic ingestion in Loggerhead Sea turtles along the Greek coastline and variations in levels of ingested plastics amongst sea turtles' life stages. [ABSTRACT FROM AUTHOR]

Microplastic pollution is a growing cause of concern for the marine environment, particularly in the Mediterranean Sea, which is considered to be one of the most polluted seas worldwide. In this study, the gastrointestinal tracts of 102 bogues (Boops boops), sampled from three areas off the Catalan coast (Spain) subject to different degrees of industrialization, were analysed to assess microplastic ingestion and thus estimate local levels of microplastic pollution. Microplastics were detected in 46% of samples analysed. As expected, the abundance and frequency of occurrence of ingested microplastics were higher off the most anthropized area of Barcelona. The majority of ingested microplastics were blue fragments ranging 0.1–0.5 mm, and the most common polymer type was polypropylene. The results of this study indicate the area off Barcelona as a possible area of concentration for microplastics, further supporting the use of B. boops as a bioindicator to assess microplastic pollution. • Levels of microplastic ingestion were assessed in bogues from the Catalan coast. • The occurrence of ingested microplastics was higher in bogues off Barcelona. • Bogues from less anthropized areas had lower amounts of microplastics in their guts. • The bogue is a suitable indicator of microplastic pollution in the Mediterranean Sea. Capsule: The results of this study indicate the area off Barcelona as a possible area of concentration of microplastics and support the use of Boops boops as a suitable bioindicator for monitoring microplastic pollution in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Plastic litter pollution is increasing in the seas and oceans worldwide, raising concern on the potential effects of plasticizer additives on marine fauna. In this study, muscle samples of 30 bogues (Boops boops; Linneaus, 1758) from the North Western Mediterranean Sea were analysed to assess the concentrations of 19 organophosphate flame retardant (OPFR) compounds and to inspect any relationship with microplastic ingestion and relative levels of anthropization. Out of the 19 OPFRs analysed, 6 compounds were detected, being tri-n-butyl phosphate (TNBP), 2-ethylhexyldiphenyl phosphate (EHDPP) and triphenylphosphine oxide (TPPO) the most abundant. As expected, OPFR concentrations were higher in samples collected off the most anthropized area of the city of Barcelona than in those from the Cap de Creus Marine Protected Area, while no significant correlation was detected between OPFR concentrations and microplastic ingestion. The results of this manuscript provide a first evidence of OPFR presence in the muscle of the bogue and identify the coastal area off Barcelona as a possible concentration area for contaminants, further supporting the use of the bogue as an indicator species of plastic pollution in the Mediterranean Sea. • OPFRs were analysed in the muscle of bogues from the NW Mediterranean Sea. • OPFR concentrations were higher in fish from the area off the city of Barcelona. • No relationship was detected between OPFR levels and microplastic ingestion. • Tri-n-butyl phosphate (TNBP) was the most abundant OPFR in both studied areas. • ΣOPFRs ranged from nd to 1,194 ng g−1 lipid weight basis. [ABSTRACT FROM AUTHOR]