Microplastics in fish and sediments from the Montenegrin coast (Adriatic Sea): Similarities in accumulation

Microplastic pollution in the littoral environment: insights from the largest Mediterranean Sabellaria spinulosa (Annelida) reef and shoreface sediments

Littoral environments represent the main entry point for pollutants into the sea. Microplastics (MPs) are a growing concern, especially for the Mediterranean basin characterized by densely populated coasts and a semi-enclosed morphology. This article targets MPs associated with a unique coastal habitat - the largest bioconstruction in the Mediterranean (Torre Mileto, Southern Adriatic Sea) built by the reef-building polychaete Sabellaria spinulosa (anellida). We assessed MPs abundance in samples from both bioconstruction and surrounding sediments using stereomicroscopy with UV light and micro-Raman spectroscopy. MPs distribution was analyzed according to substrate (reef vs. sediment), longshore drift (west vs. east side), and reef morphology (hummock vs. platform). Results showed a significantly higher MPs abundance in samples from the western side of the site, potentially related to a longshore drift influence on pollutant distribution. By contrast, no significant differences in MPs abundances were observed in substrates (reefs vs. surrounding sediments) and in reef morphologies (hummock vs. platform), which suggest no direct control of reef-building activity in accumulating MPs. The passive accumulation of MPs, primarily driven by wave action, is likely the main factor explaining the MPs distribution. Micro-Raman Spectroscopy analysis revealed polyethylene terephthalate as the dominant polymer, and fibers as the most abundant morphology; prevalent MPs colors were colorless and black. Data provided here indicate that polychaete reefs temporarily trap MPs, retaining such pollutant in the littoral environment. The mechanism of MPs passive accumulation observed in this study raises questions about the growing risk for this bio-engineered benthic habitats.

Microplastic contamination and biological alterations in Atlantic wild fish populations, and human health risks associated to fillet consumption

This study tested the hypothesis that long-term exposure to microplastics (MPs) is causing biological alterations in North Atlantic wild populations of Trisopterus luscus (pouting) and Merluccius merluccius (hake). It also estimated the human risk of MP intake (HRI) through fillet consumption, and combined the HRI and polymer health hazard in the Risk of Intake and Polymer Hazard Index (RIPHI). Fish (103) were analysed for MPs (gastrointestinal tract, gills, liver, brain, muscle), biomarkers (physical condition, neurotoxicity, energy production, oxidative stress and damage) and general stress (Integrated Biomarker Response - IBR). After particle analysis (Fourier Transform Infrared spectroscopy, Raman spectroscopy) and data correction for contamination, MPs accounted for 77 % of 311 particles. From 103 fish, 79 % contained MPs. The overall mean concentration ±SD was 0.09 ± 0.09 MP g-1 (2.32 ± 2.35 MPs ind-1) with no significant interspecific differences (p > 0.05). Among body sites, brain had the highest MP concentration (pouting: 0.6 MP g-1; hake: 0.5 MP g-1). Most abundant polymers were polyethylene (40 %), polypropylene (21 %) and polymethyl methacrylate (12 %). Fragments (<150 μm) predominated. MP profiles pointed to prey-predator transfer. Fish with MPs had higher stress levels (IBR, pouting: 0.317; hake: 0.200) than specimens without MPs (pouting: 0.0; hake: 0.062). Oxidative stress was the effect most clearly linked to MPs. Hake fillet poses lower HRI (e.g., 0.2 to 1.5 MPs day-1) than pouting fillet (e.g., 0.4 to 3.0 MPs day-1). RIPHI values showed the opposite trend (e.g., hake: 138 to 1038; pouting: 113 to 845), indicating medium to high risk to human consumers. Findings related long-term MPs exposure in the natural habitat with biological alterations in wild fish populations, highlight the importance of food diversification for a healthy alimentation, and stress the urgent need of reducing MPs pollution to promote ecosystem sustainability and global health.

Microplastics induce toxic effects in fish: Bioaccumulation, hematological parameters and antioxidant responses

This study investigates the toxic effects of microplastics by assessing bioaccumulation, hematological parameters, and antioxidant responses in juvenile Korean bullhead (Pseudobagrus fulvidraco) exposed to polyamide microplastics (PA-MPs). The increasing release of plastics into aquatic environments leads to their degradation into microplastics, which pose a significant threat to freshwater ecosystems. To evaluate these impacts, P. fulvidraco (mean length: 16.3 ± 1.1 cm, mean weight: 38.2 ± 6.6 g) were exposed to waterborne PA-MPs (white, spherical particles) at concentrations of 0, 10, 20, 5000 and 10,000 mg/L for 96 h. Bioaccumulation analysis revealed that PA-MPs primarily accumulated in the intestine, followed by the gills and liver. Hematological assessments showed significant reductions in hemoglobin and hematocrit levels at high PA-MP concentrations (5000 and 10,000 mg/L). Plasma biochemical analysis indicated significant alterations in calcium, magnesium, glucose, cholesterol, total protein, AST, ALT and ALP levels. In terms of antioxidant responses, superoxide dismutase (SOD) and catalase (CAT) activities increased significantly with PA-MP exposure, while glutathione S-transferase (GST) activity showed a marked decrease. These findings suggest that PA-MP exposure leads to bioaccumulation in key tissues and induces physiological stress in P. fulvidraco by altering hematological and antioxidant defense mechanisms, highlighting the potential toxicity of microplastics in freshwater fish.

Natural and Regenerated Cellulosic Microfibers Dominate Anthropogenic Particles Ingested by Commercial Fish Species from the Adriatic Sea

This study investigated the occurrence of fibrous microplastics and natural and artificial cellulose microfibers in the gastrointestinal tracts of Mullus barbatus and Merluccius merluccius specimens from the Adriatic Sea (Central Mediterranean), an important hotspot for marine litter accumulation. Red mullet and European hake were chosen due to their roles as bioindicators of marine pollution in the Mediterranean, and their economic relevance as fishery resources. Microfibers were found in 72% of M. barbatus and 68% of M. merluccius, at levels ranging from 1 to 67 particles/individual. Most of the microfibers extracted were textile fibers that were blue (33.6%), clear (26.1%), and black (20.3%) in color, while the length distribution showed the prevalence of microfibers in the size range of 350-950 µm. This visual identification, corroborated by the micro-FTIR analysis of a sub-sample of microfibers, revealed that natural and artificial cellulose microfibers were more common (80%) than fibrous microplastics. The results confirmed that both of these fish species are susceptible to microfiber ingestion and indicated the high availability of natural and artificial cellulosic fibers in the Adriatic Basin. Despite the increased evidence of microfiber pollution in the marine ecosystem, only a limited number of studies examine natural/artificial microfiber contamination and ingestion by marine biota. Therefore, greater attention should be given to this new type of contaminant, considering its implications in terms of environmental health, food security, and food safety.

Beach wracks microbiome and its putative function in plastic polluted Mediterranean marine ecosystem

The coasts of the world's oceans and seas accumulate various types of floating debris, commonly known as beach wracks, including organic seaweeds, seagrass, and ubiquitous anthropogenic waste, mainly plastic. Beach wrack microbiome (MB), surviving in the form of a biofilm, ensures decomposition and remineralization of wracks, but can also serve as a vector of potential pathogens in the environment. Through the interdisciplinary approach and comprehensive sampling design that includes geological analysis of the sediment, plastic debris composition analysis (ATR-FTIR) and application of 16S rRNA gene metabarcoding of beach wrack MBs, this study aims to describe MB in relation to beach exposure, sediment type and plastic pollution. Major contributors in beach wrack MB were Proteobacteria, Bacteroidetes, Actinobacteria, Planctomycetes, Verrucomicrobia and Firmicutes and there was significant dissimilarity between sample groups with Vibrio, Cobetia and Planococcus shaping the Exposed beach sample group and Cyclobacteriaceae and Flavobacterium shaping the Sheltered beach sample group. Our results suggest plastisphere MB is mostly shaped by beach exposure, type of seagrass, sediment type and probably beach naturalness with heavy influence of seawater MB and shows no significant dissimilarity between MBs from a variety of microplastics (MP). Putative functional analysis of MB detected plastic degradation and potential human pathogen bacteria in both beach wrack and seawater MB. The research provides the next crucial step in beach wrack MP accumulation research, MB composition and functional investigation with focus on beach exposure as an important variable.

Immunotoxicity of microplastics in fish

Plastic waste degrades slowly in aquatic environments, transforming into microplastics (MPs) and nanoplastics (NPs), which are subsequently ingested by fish and other aquatic organisms, causing both physical blockages and chemical toxicity. The fish immune system serves as a crucial defense against viruses and pollutants present in water. It is imperative to comprehend the detrimental effects of MPs on the fish immune system and conduct further research on immunological assessments. In this paper, the immune response and immunotoxicity of MPs and its combination with environmental pollutants on fish were reviewed. MPs not only inflict physical harm on the natural defense barriers like fish gills and vital immune organs such as the liver and intestinal tract but also penetrate cells, disrupting intracellular signaling pathways, altering the levels of immune cytokines and gene expression, perturbing immune homeostasis, and ultimately compromising specific immunity. Initially, fish exposed to MPs recruit a significant number of macrophages and T cells while activating lysosomes. Over time, this exposure leads to apoptosis of immune cells, a decline in lysosomal degradation capacity, lysosomal activity, and complement levels. MPs possess a small specific surface area and can efficiently bind with heavy metals, organic pollutants, and viruses, enhancing immune responses. Hence, there is a need for comprehensive studies on the shape, size, additives released from MPs, along with their immunotoxic effects and mechanisms in conjunction with other pollutants and viruses. These studies aim to solidify existing knowledge and delineate future research directions concerning the immunotoxicity of MPs on fish, which has implications for human health.

Proposed validation stages for MPs extraction from edible mussels (Mytilus galloprovincialis)

The potential presence of microplastics (MPs) in seafood products presents significant health concerns, demanding the adoption of standardized and validated methodologies. In this study, we introduce a validated method and an innovative technique for extracting MPs from mussels using an oxidizing agent, Corolase enzyme, and a surfactant, thus eliminating the need for mechanical agitation. Evaluation of the extraction process focused on three critical parameters: recovery percentage, repeatability, and chemical integrity, along with color stability. To ensure precision and reliability, low-density infrared spectroscopy (LDIR) was employed to analyze the effect of spectrum quality (Q). Ultimately, this methodology was applied to identify MPs in commercial mussels, with results showcasing the viability of the proposed validation stages for MPs extraction, maintaining MPs integrity with high recovery percentages.

A study on textile microfiber contamination in the gastrointestinal tracts of Merluccius merluccius samples from the Tyrrhenian Sea

The increased demand and consumption of synthetic textiles have contributed to microplastic pollution in the form of microfibers. These particles are widely spread in the aquatic environment, leading to the exposure of marine biota, including edible species. The current study aimed to assess the extent of microfiber contamination in a commercially relevant fish species, Merluccius merluccius, which is considered a small-scale bioindicator for the monitoring of plastic ingestion in the Mediterranean coastal environment. The frequency of ingestion, abundance, and composition of textile microfibers isolated from the fish gut were characterized. Results showed the occurrence of microfibers in 75% of the samples, with a mean number of 10.6 microfibers/individual, of which 70% were classified as natural microfibers. The spectroscopic analyses confirmed both the visual identification of microfibers and the prevalence of cellulosic fibers. The obtained findings provided evidence of both natural/artificial and synthetic microfiber exposure in an important commercial fish species that, considering the consumption of small individuals without being eviscerated, may be a potential route of microfiber exposure in humans. Monitoring programs for fishery products from markets are needed to assess contamination levels and human health risks. In addition, measures to control microfiber pollution need to occur at multiple levels, from textile industries to international governments.

The EU Interreg Project "ADRINET": Assessment of Well-Known and Emerging Pollutants in Seafood and Their Potential Effects for Food Safety

Anthropogenic activities lead to the spread of chemicals and biological materials, including plastic waste, toxic metals, and pharmaceuticals, of which the impact on the Mediterranean Sea is of high concern. In this context, the EU Interreg Italy-Albania-Montenegro Project "ADRINET (Adriatic Network for Marine Ecosystem) _244" (2018-2020) arises. It aims to carry out biomonitoring campaigns in the main commercial interest of fish and cephalopod species, such as Sparus aurata, Dicentrarchus labrax, Sepia spp., and Loligo spp. sampled in three different subregions of the Mediterranean Sea. The presence of the main environmental contaminants, such as cadmium, microplastics, and antibiotics was investigated in these seafood samples. Contamination by cadmium and antibiotics in the seafood investigated in our study was negligible. However, a high value of microplastics was detected in the stomach and gut of Sparus aurata and Dicentrarchus labrax. Overall, even though the presence of microplastics needs to be investigated by further studies, the results confirmed that the environmental conditions of the three bays investigated by the ADRINET project partners (Italy, Albania, Montenegro) are positive and not affected by intensive anthropogenic activity.

Microplastic pollution in rivers of the Adriatic Sea basin in Montenegro: Impact on pollution of the Montenegrin coastline

Concern regarding microplastic (MP) pollution in aquatic ecosystems has increased in recent years with growing awareness of the environmental harm that it causes. While most studies have focused on seas and oceans, knowledge of MP occurrence in freshwater sediments is limited. This study investigated MP concentrations at shore sediments of the Zeta, Morača, and Bojana rivers in Montenegro. The MP concentration in the studied samples varied depending on the river, location, and sampling season. MP abundance in river shore sediments varied between mean values of 145 ± 110 MPs/kg for the Zeta, 169 ± 113 MPs/kg for the Morača, and 180 ± 53.5 MPs/kg dry sediment for the Bojana. In comparison, the mean MP abundance in the three rivers combined was 163.6 ± 96.1 MPs/kg of dry sediment. The identified MPs were mainly fibres and fragments of blue, red and clear color, 0.5-1 mm in size, and mainly composed of polyethylene, polypropylene, polyamide and polyethylene terephthalate. The main contribution of this study is that it provides new insight into MP abundance in freshwater sediments of rivers, where the studied rivers were identified as a potential important sink and source of MP on the Montenegrin coast.

High microplastics concentration in liver is negatively associated with condition factor in the Benguela hake Merluccius polli

Microplastics (MPs) affect both marine and terrestrial biota worldwide for their harmful effects, which range from physical cell damage to physiological deterioration. In this research, microplastics were quantified from gills, liver and muscle of demersal Benguela hakes Merluccius polli (n = 94), caught by commercial trawling from northwest African waters. Plastic polymers were identified using Fourier Transformed-infraRed spectroscopy (FT-iR). Fulton's k condition factor and the degree of DNA degradation in liver were measured. None of the individuals were free of MPs, whose concentration ranged from 0.18 particles/g in muscle to 0.6 in liver. Four hazardous polymers were identified: 2-ethoxyethylmethacrylate, polyester, polyethylene terephthalate, and poly-acrylics. MP concentration in liver was correlated negatively with the condition factor, suggesting physiological damage. Positive association of MP concentration and liver DNA degradation was explained from cell breakage during trawl hauls during decompression, suggesting an additional way of MPs harm in organisms inhabiting at great depth. This is the first report of potential MPs-driven damage in this species; more studies are recommended to understand the impact of MP pollution on demersal species.

Nanoplastics pose a greater effect than microplastics in enhancing mercury toxicity to marine copepods

Due to human activities, high abundances of nano/microplastics (N/MPs) concurrent with metal pollution have become a serious problem in the global marine environment. Because of displaying a high surface-area-to-volume ratio, N/MPs can serve as the carriers of metals and thus increase their accumulation/toxicity in marine biota. As one of the most toxic metals, mercury (Hg) causes adverse effects on marine organisms but whether environmentally relevant N/MPs can play a vector role of this metal in marine biota, as well as their interaction, is poorly known. To evaluate the vector role of N/MPs in Hg toxicity, we first performed the adsorption kinetics and isotherms of N/MPs and Hg in seawater, as well as ingestion/egestion of N/MPs by marine copepod Tigriopus japonicus, and second, the copepod T. japonicus was exposed to polystyrene (PS) N/MPs (500-nm, 6-μm) and Hg in isolation, combined, and incubated forms at environmentally relevant concentrations for 48 h. Also, the physiological and defense performance including antioxidant response, detoxification/stress, energy metabolism, and development-related genes were assessed after exposure. The results indicated N/MPs significantly increased Hg accumulation and thus its toxicity effects in T. japonicus as exemplified by decreased transcription of genes related to development and energy metabolism and increased transcriptional levels of genes functioning in antioxidant and detoxification/stress defense. More importantly, NPs were superimposed onto MPs and produced the most vector effect in Hg toxicity to T. japonicus, especially in the incubated forms. Overall, this study highlighted the role of N/MPs as a potential risk factor for increasing the adverse effects of Hg pollution, and emphasized the adsorption forms of contaminants by N/MPs should doubly be considered in the continuing researches.

Microplastics in mussels from the Boka Kotorska Bay (Adriatic Sea) and impact on human health

This study evaluated the microplastic abundance, shape, color, size and chemical composition of microplastic in mussels and estimated human exposure to microplastic through consumption of mussels collected from Boka Kotorska Bay (Adriatic coast of Montenegro). Microplastic was found in 53.3% of the studied mussels, with an average microplastic abundance of 2.53 ± 1.1 items/individual. Most of the ingested microplastic were fibers (63.7%), which were blue in color. FT-IR revealed that 98% of the examined particles were plastic, with seven polymers identified, of which polyethylene, polypropylene, and polyethylene terephthalate were the most abumdant polymers in mussels. Three of the polymers detected in mussels (polyamide, polyvinyl chloride and polystyrene) are classified as hazardous by the European Chemical Agency with warning or danger signals. With one serving of mussels, consumers would ingest 22.7 microplastic particles, while the annual dietary intake of microplastic via consumption of mussels was estimated at 99 MP/year.

Content of Trace Elements and Human Health Risk Assessment via Consumption of Commercially Important Fishes from Montenegrin Coast

Muscle tissues of Mullus barbatus and Merluccius merluccius were analyzed for the presence of selected trace elements (As, Hg, Cd, and Pb) to determine the value of the daily intake of trace elements from fish consumption and to assess the risk to human health. The mean concentrations of As in the muscle tissue of M. barbatus and M. merluccius for the entire period were 19.689 mg/kg wet weight (ww) and 8.356 mg/kg ww, Hg 0.497 mg/kg ww and 0.153 mg/kg ww, and Pb 0.031 mg/kg ww and 0.025 mg/kg ww, respectively. The concentrations of Cd in all fish sampled were below the detection limit (<0.02 mg/kg ww). The evaluation of the potential health risk assessments based on the target hazard quotient (THQ) and estimated daily intake (EDI) indicated that the intake of As in both fish species and Hg for M. barbatus could pose an appreciable risk to human health. The calculated hazard index (HI) was higher than 1 for both fish species. The continuous monitoring of trace elements' concentrations in fish is strongly recommended, as the results demonstrate potential health risks due to the presence of As and Hg.