Synthetic polymers: A global threat to aquatic benthic environments.

Finding time-efficient and cost-effective data collection methods is a challenge when addressing aquatic litter pollution on a global scale. In this study, we analysed data on aquatic benthic debris collected worldwide by volunteer scuba divers through the Dive Against Debris® citizen science initiative, examining its relationship with spatial and socio-economic factors. Plastic-dominated litter was found in both marine (64 %) and freshwater (48 %) environments, followed by metal and glass. Lower litter abundances have been recorded in high income countries such as in Europe, Central Asia and North America. Plastic fragments and fishing lines were the most abundant seafloor litter items, while takeaway containers (aluminium cans, glass bottles) were dominant in freshwater environments. Single-use plastics, including objects for food and beverage consumption, accounted for about 1/3 of the total benthic aquatic debris. Our findings highlight the need to prioritise the fishing industry and change our fast-paced modern lifestyle. Citizen science initiatives, once data cleanup is conducted to overcome any bias, can provide valuable tools for better understanding and quantifying marine litter pollution. The outcomes gained can be leveraged to improve consumer awareness and inform environmental policies aimed at addressing aquatic litter pollution more effectively.

Not only in the crowd: Benthic litter characterization in a low population density area still reveals widespread pollution and local malpractices.

Various anthropogenic activities affect marine coastal habitats, leading to heavy litter pollution. However, whilst high litter concentrations are nowadays common in the proximity of metropolises, few studies investigated the magnitude of this phenomenon around coastal villages and small towns. We hereby characterized the benthic litter occurring in the trawlable grounds of the Gulf of Policastro (Tyrrhenian Sea, central-western Mediterranean), a low population density area that becomes a popular tourist destination during summer. We furthermore tested differences between two depths (∼100-200 and ∼500-600 m) and the impact of tourism on the shallower waters. The area was characterized by a litter abundance of 651.12 ± 130.61 item/km2, with plastic being almost totalitarian (93%). The shallower waters hosted two-thirds of the litter found. Almost all (∼95%) the litter items had a land-based origin, while the sea-based litter was mostly found at higher depths. About 14% of the litter was found to be fouled, with the development of litter-associated communities that somehow mimic the natural ones living on hard substrates. The higher litter presence noticed during the touristic peak (July-August) suggests that tourism is an important source of local litter, although it contributed to the local accumulation in a synergic way with other factors. The majority of the litter items presumably originated from the nearby coastline, while the deeper waters were or are used as a dumping site by the local trawling fleet. The discovery of such a critical waste accumulation and management in a somehow remote area contributes to widen the perspectives on the presence of benthic litter mostly in territories characterized by wide anthropization. Moreover, it confirms that appropriate local policies and communication plans are urged even at a regional level to stimulate citizen consciousness and mitigate the ever growing litter pollution.

A glimpse into the future: A suitable methodological approach for the detection and identification of micro-bioplastics in biota.

In the frame of the circular economy, bioplastics are considered a good alternative to conventional plastic materials. Until recently, only a few studies have focused on the occurrence and impact of bio-microplastics (bio-MPs) in aquatic environments, and there is a lack of a methodological approach to measure their amount in marine compartments. This research aimed to identify and validate a method for bio-MPs extraction from biota. A chemical digestion protocol suitable for conventional MPs, using potassium hydroxide (KOH), was applied for the detection, in mussels, of MPs made with Mater-Bi (MBi) from socks used in mussel farming. This method was tested on virgin MBi (VMBi) and aged (AMBi) MPs, ranging from 200 to 1000 µm in presence and absence of mussel tissues. Samples were analysed in pre- and post-digestion steps to assess the recovery rate, potential visual and size changes and polymer alteration in different bio-MPs size ranges. Results showed that MBi seems to be affected by KOH under pre-production conditions (VMBi), whereas in the AMBi treatment, which represents the environmentally realistic condition, the presence of fouling due to deployment at sea preserves MBi from the action of the alkaline agent. This approach allowed the recovery of small MPs, generally difficult to extract from biota, in an optimal visual condition and without polymer alteration. Despite the fraction of organic material in the MBi, these results suggested the suitability of this method and provided the assessment of the KOH effects on MBi-MPs under different environmental conditions. Finally, validation tests proved that the KOH protocol represents a reliable approach for detecting bio-MPs in marine organisms. This study is an important starting point for assessing the impact of the bio-MPs on the marine environment and suggests future studies to improve these issues in order to fill the gaps in the field of bioplastics.

How Rare Are Argonautoidea Octopuses in the Mediterranean? New Data from Stranding Events, Stomach Contents and Genetics.

The present paper represents the first all-encompassing study on all Mediterranean holopelagic octopods belonging to Argonautoidea (Argonauta argo, Ocythoe tuberculata, Tremoctopus gracilis, Tremoctopus violaceus). Argonautoidea octopuses were collected by different sampling methods in the Strait of Messina and southern Tyrrhenian Sea. The aim of this paper was to improve knowledge, using information from different data sources, such as the study of stranded individuals or accidental caught specimens, as well as the analysis of stomach content of large pelagic fishes. Moreover, we investigated their taxonomic profile through the amplification of the mitochondrial cytochrome c oxidase subunit I (COI). Overall, 47 fresh holopelagic octopods were collected, including valuable records of rare males. Moreover, 330 Argonautoidea octopuses were found in the stomachs of 800 predators. The results provided evidence that these cephalopods are more abundant than thought in the past. The molecular approach supported the ecological results with interesting insights. The similarity-based identifications and tree-based methods indicated that three females could be identified as Tremoctopus violaceus in agreement with their morphological classifications. The sequences obtained from the two T. gracilis individuals were clustered with the sequences of Tremoctopus violaceus from the Gulf of Mexico and were differentiated from the sequences attributed to T. gracilis and T. robsoni. The study represents a valuable contribution to the genetic characterization of Mediterranean individuals of the genera Tremoctopus, Argonauta and Ocythoe.

Integrated approach for marine litter pollution assessment in the southern Tyrrhenian Sea: Information from bottom-trawl fishing and plastic ingestion in deep-sea fish.

Marine litter pollution threatens marine ecosystems and biodiversity conservation, particularly on seafloors where all anthropogenic waste naturally sinks. In this study, we provide new information on the composition, density and origin of seafloor macrolitter as well as on plastic ingestion in deep-sea fish from bottom-trawling by-catch in the southern Tyrrhenian Sea. Plastic constituted the highest fraction of litter in terms of density (64 %) and weight (32 %) and was also retrieved in the gastrointestinal traits of Chlorophthalmus agassizi, Coelorhynchus coelorhynchus and Hoplosthethus mediterraneus. FT-IR spectroscopy analysis on the seafloor macrolitter and the ingested plastics revealed the presence of artificial polymers including PE, PET/polyester, PA widely used for food packaging, plastic bags and several common products, especially Single Use Plastic (SUP). These results underline how poor waste management schemes or their incorrect application strongly contribute to marine litter accumulation on seafloors and plastic ingestion in deep-sea fish.

Importance of the Lunar Cycle on Mesopelagic Foraging by Atlantic Bluefin Tuna in the Upwelling Area of the Strait of Messina (Central Mediterranean Sea).

The influence of the lunar cycle on bluefin tuna foraging in the upwelling area of the Strait of Messina was investigated by exploring trophic interaction with mesopelagic fish and cephalopod prey. To focus on how the lunar cycle could affect availability of mesopelagic prey for this predator, we tested potential differences in the diet related to each lunar phase. Moreover, we considered two potential impacts of the lunar cycle: the lunar irradiance and the strength of currents. Overall, 2672 prey items were mesopelagic fish and cephalopods, representing 60.7% of overall diet by number. The main mesopelagic fish prey items were lanternfishes and dragonfishes, while Onychoteuthis banksii was the most important cephalopod prey. In summary, the Strait of Messina has highly specific hydrodynamic and biological features which strongly depend on upwelling currents, which in turn are influenced by the lunar cycle (new and full moon with strong currents, quarters with fewer currents). Upwelling causes water mixing, bringing to the surface a large amount of mesopelagic fauna which become more readily available to tuna. Lunar irradiance contributes to the variation of prey composition, increasing the success of visual predation on mesopelagic resources at high light in the water column.

Integrated biomarker responses in European seabass Dicentrarchus labrax (Linnaeus, 1758) chronically exposed to PVC microplastics.

Few studies evaluated long-term effects of polyvinyl chloride (PVC) microplastics (MPs) ingestion in fish. The present study aimed to investigate the integrated biomarker responses in the liver and blood of 162 European seabass, Dicentrarchus labrax, exposed for 90 days to control, virgin and marine incubated PVC enriched diets (0.1 % w/w) under controlled laboratory condition. Enzymatic and tissue alterations, oxidative stress, gene expression alterations and genotoxicity were examined. Additives and environmental contaminants levels in PVC-MPs, control feed matrices and in seabass muscles were also detected. The results showed that the chronic exposure at environmentally realistic PVC-MPs concentrations in seabass, cause early warning signs of toxicological harm in liver by induction of oxidative stress, the histopathological alterations and also by the modulation of the Peroxisome proliferator-activated receptors (PPARs) and Estrogen receptor alpha (ER-α) genes expression. A trend of increase of DNA alterations and the observation of some neoformations attributable to lipomas suggest also genotoxic and cancerogenic effects of PVC. This investigation provides important data to understand the regulatory biological processes affected by PVC-MPs ingestion in marine organisms and may also support the interpretation of results provided by studies on wild species.

The waste collector: information from a pilot study on the interaction between the common octopus (Octopus vulgaris, Cuvier, 1797) and marine litter in bottom traps fishing and first evidence of plastic ingestion.

Few studies focused on behaviour adaptations of organisms to marine litter (ML) pollution in Mediterranean Sea. This research, investigates on some behavior traits of Octopus vulgaris, focusing on the interaction with ML during the artisanal fishing activities by the bottom traps in a small coastal area of the southern Tyrrhenian Sea. For the first time, this pilot study uses an integrated approach based on the Fishermen Ecological Knowledge as well as the analysis of ML found in the traps. First assessment of plastic ingestion in this species are also reported. Plastic and metal were the predominant ML categories observed into the bottom traps. A total of 62 plastics, mainly small microplastics and fibres shaped, were ingested. The ML finding in the bottom traps suggests an interesting behavior of the common octopus regarding its interaction with ML, in fact, it seems to bring ML inside its dens, as a collector.

Microplastics in the bogue, Boops boops: A snapshot of the past from the southern Tyrrhenian Sea.

The present investigation focuses on Boops boops specimens gathered in the Gulf of Patti in 2010. Providing a snapshot from the past, this paper represents, chronologically, the first record of microplastic ingestion in the Mediterranean bogue. The plastic abundance and composition in gastrointestinal tracts of the bogue was assess, in order to improve the knowledge on spatial-temporal variability of microplastics pollution in the Mediterranean basin and in particular, in the southern Tyrrhenian Sea. In a total of 65 specimens, 180 particles of plastic (2.8 items/specimens), mainly belonging to microplastics class, were found. Fragments (63%) and fibres (30%) were the predominant shape categories. Eleven polymers were identified: polypropylene and polyethylene were the most abundant. Several synthetic polymers belonging to the class of elastomers were also observed. The study area is strongly influenced by the absence of trawl fishing activities and a low mixing level of the seabed that, together with the confluence of different watercourses and the presence of different kind of anthropic impact, including motorway, could make it a 'waste disposal site'. Finally, our results suggest the usefulness to retrieve older samples to better understand spatial-temporal changes in marine litter pollution over time.

Interlaboratory comparison of microplastic extraction methods from marine biota tissues: A harmonization exercise of the Plastic Busters MPAs project.

In the framework of the Plastic Busters MPAs project, a harmonization exercise on two methods of microplastic extraction from biological samples i.e. 15% H2O2 digestion and 10% KOH digestion was carried out. The two methods were tested in four laboratories on fish gastrointestinal tracts and mussel tissues spiked with polyethylene, polypropylene and polyethylene terephthalate. The recovery percentage of microplastics for each method, species and polymer tested were overall similar among laboratories, and interlaboratory coefficient of variation was less than 11% for the majority of samples. Microplastic recovery rates for the two methods were similar for each sample tested, but overall mean interlaboratory recovery rate using KOH (96.67%) was higher than H2O2 (88.75%). Results validate the use of both methods for extracting microplastics from biota tissues. However, when comparing the two methods in terms of microplastic recovery rate, time consumed, technical difficulties and cost, digestion with 10% KOH is considered optimal.

A new digestion approach for the extraction of microplastics from gastrointestinal tracts (GITs) of the common dolphinfish (Coryphaena hippurus) from the western Mediterranean Sea.

Plastic ingestion is one of the main impacts of marine litter on organisms. The occurrence of microplastics (MPs < 5 mm) in the stomachs of Mediterranean species was already reported in several studies. In this context, the present study aims to develop a new approach of digestion for the identification of MPs in the gastrointestinal tracts (GITs) of marine organisms. The new approach combines two digestion protocols, including potassium hydroxide (KOH) and nitric acid (HNO3), to remove most organic and inorganic materials. This digestion allows recording small MPs that are difficult to find via routinely stomach content analysis and also to minimize the overestimation of the phenomenon trough the control of airborne contamination. The new approach was tested on a voracious pelagic opportunistic predator, the common dolphinfish, a fishery resource exploited in several Mediterranean areas. The results showed that a large amount of ingested meso- and microplastics, such as fragments or sheets, was recorded in GITs (F = 65.5 %). The FTIR analysis on litter samples allowed to identify polyethylene, polypropylene and polystyrene as dominant constituent polymers of microplastics. These results confirmed that our novel combined digestion protocol represents a reliable approach to detect MPs in opportunistic pelagic predators.

Colonization of floats from submerged derelict fishing gears by four protected species of deep-sea corals and barnacles in the Strait of Messina (central Mediterranean Sea).

The distribution of floating litter in marine waters, influenced by currents and wind drag, often determines the dispersal of its encrusting fauna. In the present paper, we observed for the first time the colonization of rafting floats from abandoned, lost or derelict fishing gears (ALDFG) by the four protected deep-sea species: Errina aspera, Desmophyllum pertusum, Madrepora oculata Pachylasma giganteum. Overall, 41 floats, colonized by deep benthic species, were found stranded on the shore of the Sicilian coast of the Strait of Messina, between 2016 and 2019. Species composition, number and occurrence of colonizing organisms were analyzed. On the basis of the species composition (the association between E. aspera, P. giganteum and Megabalanus tulipiformis), the knowledge on their ecology, biogeography, path of local currents, it was possible to define that the area of origin of the most part of these fishing net floats was the Strait of Messina.

Effects of microplastics on trophic parameters, abundance and metabolic activities of seawater and fish gut bacteria in mesocosm conditions.

Plastic pollution is an emerging threat with severe implications on animals' and environmental health. Nevertheless, interactions of plastic particles with both microbial structure and metabolism are a new research challenge that needs to be elucidated yet. To improve knowledge on the effects played by microplastics on free-living and fish gut-associated microbial community in aquatic environments, a 90-day study was performed in three replicated mesocosms (control-CTRL, native polyvinyl chloride-MPV and weathered polyvinyl chloride-MPI), where sea bass specimens were hosted. In CTRL mesocosm, fish was fed with no-plastic-added food, whilst in MPV and MPI food was supplemented with native or exposed to polluted waters polyvinylchloride pellets, respectively. Particulate organic carbon (POC) and nitrogen, total and culturable bacteria, extracellular enzymatic activities, and microbial community substrate utilization profiles were analyzed. POC values were lower in MPI than MPV and CRTL mesocosms. Microplastics did not affect severely bacterial metabolism, although enzymatic activities decreased and microbes utilized a lower number of carbon substrates in MPI than MPV and CTRL. No shifts in the bacterial community composition of fish gut microflora were observed by denaturing gradient gel electrophoresis fingerprinting analysis.

Marine litter in an EBSA (Ecologically or Biologically Significant Area) of the central Mediterranean Sea: Abundance, composition, impact on benthic species and basis for monitoring entanglement.

Marine litter is commonly observed everywhere in the ocean. In this study, we analyzed 17 km of video footage, collected by a Remotely Operated Vehicle (ROV) at depths ranging between 20 and 220 m, during 19 transects performed on the rocky banks of the Straits of Sicily. Recently, the Contracting Parties of the Convention on Biological Diversity (CBD) recognized this site as an Ecologically or Biologically Significant Area (EBSA). The research aim was to quantify the abundance of marine litter and its impact on benthic fauna. Litter density ranged from 0 items/100 m2 to 14.02 items/100 m2 with a mean (±standard error) of 2.13 (±0.84) items/100 m2. The observed average density was higher (5.2 items/100 m2) at depths >100 m than at shallower depths (<100 m, 0.71 items/100 m2). Lost or abandoned fishing lines contributed to 98.07% of the overall litter density, then representing the dominant source of marine debris. Litter interactions with fauna were frequently observed, with 30% of litter causing "entanglement/coverage" and 15% causing damage to sessile fauna. A total of 16 species showed interaction (entanglement/coverage or damage) with litter items and 12 of these are species of conservation concern according to international directives and agreements (CITES, Berne Convention, Habitat Directive, SPA/BD Protocol, IUCN Red List); we also observed 7 priority habitats of the SPA/BD Protocol. This research will support the implementation of monitoring "Harm" as recommended by the UN Environment/MAP Regional Plan on Marine Litter Management in the Mediterranean, and the Marine Strategy Framework Directive (MSFD). The institution of a SPAMI in the investigated area could represent a good management action for the protection of this hotspot of biodiversity and to achieve a Good Environmental Status (GES) for the marine environment by 2020, under the MSFD.

Bioindicators for monitoring marine litter ingestion and its impacts on Mediterranean biodiversity.

The Mediterranean Sea has been described as one of the most affected areas by marine litter in the world. Although effects on organisms from marine plastic litter ingestion have been investigated in several oceanic areas, there is still a lack of information from the Mediterranean Sea. The main objectives of this paper are to review current knowledge on the impact of marine litter on Mediterranean biodiversity, to define selection criteria for choosing marine organisms suitable for use as bioindicator species, and to propose a methodological approach to assessing the harm related to marine litter ingestion in several Mediterranean habitats and sub-regions. A new integrated monitoring tool that would provide the information necessary to design and implement future mitigation actions in the Mediterranean basin is proposed. According to bibliographic research and statistical analysis on current knowledge of marine litter ingestion, the area of the Mediterranean most studied, in terms of number of species and papers in the Mediterranean Sea is the western sub-area as well as demersal (32.9%) and pelagic (27.7%) amongst habitats. Applying ecological and biological criteria to the most threatened species obtained by statistical analysis, bioindicator species for different habitats and monitoring scale were selected. A threefold approach, simultaneously measuring the presence and effects of plastic, can provide the actual harm and sub-lethal effects to organisms caused by marine litter ingestion. The research revealed gaps in knowledge, and this paper suggests measures to close the gap. This and the selection of appropriate bioindicator species would represent a step forward for marine litter risk assessment, and the implementation of future actions and mitigation measures for specific Mediterranean areas, habitats and species affected by marine litter ingestion.

Intestinal alterations in European sea bass Dicentrarchus labrax (Linnaeus, 1758) exposed to microplastics: Preliminary results.

This study investigates, for the first time, the intestinal responses of European sea bass Dicentrarchus labrax chronically exposed to microplastics through ingestion. Fish (n = 162) were fed with 3 different treatment diets for 90 days: control, native polyvinyl chloride (PVC) and polluted polyvinyl chloride (PVC) pellets. Intestines were fixed and processed for histological analysis using standard techniques. Histopathological alterations were examined using a score value (from 0 to 4). The distal part of intestine in all samples proved to be the most affected by pathological alterations, showing a gradual change varying from moderate to severe related to exposure times. The histological picture that characterizes both groups especially after 90 days of exposure, suggests that the intestinal functions can be in some cases totally compromised. The worst condition is increasingly evident in the distal intestine of fish fed with polluted PVC pellets respect to control groups (p < 0.05) to different exposure times. These first results underline the need to assess the impact of increasing microplastics pollution on the marine trophic web.

First evidence of presence of plastic debris in stomach of large pelagic fish in the Mediterranean Sea.

This study focuses, for the first time, on the presence of plastic debris in the stomach contents of large pelagic fish (Xiphias gladius, Thunnus thynnus and Thunnus alalunga) caught in the Mediterranean Sea between 2012 and 2013. Results highlighted the ingestion of plastics in the 18.2% of samples. The plastics ingested were microplastics (<5mm), mesoplastics (5-25mm) and macroplastics (>25mm). These preliminary results represent an important initial phase in exploring two main ecotoxicological aspects: (a) the assessment of the presence and impact of plastic debris on these large pelagic fish, and (b) the potential effects related to the transfer of contaminants on human health.