Assessment and accumulation of microplastics in the Indian riverine systems: Risk assessment and implications of translocation across the water-to-fish continuum.

Microplastic (MP) pollution has engulfed global aquatic systems, and the concerns about microplastic translocation and bioaccumulation in fish and other aquatic organisms are now an unpleasant truth. In the past few years, MP pollution in freshwater systems, particularly rivers and subsequently in freshwater organisms, especially in fish, has caught the attention of researchers. Rivers provide livelihood to approximately 40 % of the global population through food and potable water. Hence, assessment of emerging contaminants like microplastics in rivers and the associated fauna is crucial. This study assessed microplastics (MPs) in fish, sediment and freshwater samples across the third largest riverine system of peninsular India, the Mahanadi River. The number concentrations of MPs measured in water, sediment and fish ranged from 337.5 ± 54.4-1333.3 ± 557.2 MPs/m3, 14.7 ± 3.7-69.3 ± 10.1 MPs/kg. Dry weight and 0.4-3.2 MPs/Fish, respectively. Surprisingly, MPs were found in every second fish sample, with a higher MP number in the gut than in the gills. Black and blue coloured filaments with <0.5 mm size were the dominant MPs with polypropylene and polyethylene polymers in abundance. The Polymer Hazard Index (PHI) and the Potential Ecological Risk Index (PERI) studies revealed that the majority of the sampling sites fell in Risk category V (dangerous category). An irregular trend in the MP concentration was observed downstream of the river, though relatively elevated MP concentrations in water and fish samples were observed downstream of the river. t-Distributed Stochastic Neighbour Embedding (t-SNE) unveiled distinct patterns in MP distribution with a higher similarity exhibited in the MPs found in fish gill and gut samples, unlike water and sediment, which shared certain characteristics. The findings in the current study contribute to filling the knowledge gap of MP assessment and accumulation in global freshwater systems and highlight the microplastic contamination and accumulation in fish with its potential implications on human health.

First assessment of Rare Earth Element organotropism in Solea solea in a coastal area: The West Gironde Mud Patch (France).

Few studies exist on concentration and internal distribution of Rare Earth Elements (REEs) in marine fishes. REEs organotropism was determined in common sole (Solea solea) from the West Gironde Mud Patch (WGMP; N-E Atlantic Coast, France). The highest ∑REEs concentrations occurred in liver (213 ± 49.9 µg kg-1 DW) and gills (119 ± 77.5 µg kg-1 DW) followed by kidneys (57.7 ± 25.5 µg kg-1 DW), whereas the lowest levels were in muscles (4.53 ± 1.36 µg kg-1 DW) of Solea solea. No significant age- or sex-related differences were observed. The organotropism varied among groups of REEs. Light and heavy REEs preferentially accumulated in liver and gills, respectively. All considered organs showed different normalized REEs patterns, suggesting differences in internal distribution processes between organs. Further work should address: (1) baseline levels worldwide, and (2) factors controlling uptake and organ-specific concentration of REEs.

The Effect of Zinc Concentration on Physiological, Immunological, and Histological Changes in Crayfish (Procambarus clarkii) as Bio-indicator for Environment Quality Criteria.

The release of heavy metals to the environment increased dramatically with industrialization and rapid economic development, and they have accumulated in aquatic organisms. The current study aimed toe valuate the physiological, immunological, and histological changes of crayfish (Procambarus clarkii) as bio-indicator for water quality. Crayfishes of the filed study group were collected from a polluted area (Rosetta branch, Egypt), where the highest concentration for heavy metals in water was for zinc (Zn). Besides the field study group, other crayfishes were exposed to different doses of ZnSO4 (0, 203, and 406 mg L-g) corresponding to Zn concentration (0, 46.03, and 92.06 mg L-1) respectively in aquariums for consecutive 4 days. Heavy metal concentrations in field water sample were arranged as follows: Zn > Fe> Pb > Cu and Mn > Ni > Co > Cd. The result revealed that Zn bioaccumulation increases significantly with the increase of water Zn concentration among the tested groups compared to the control group, where the highest bioaccumulation in all studied tissues (hepatopancreas, gills, and muscles) was observed in the field group and Zn high-dose group. Also, there was a significant increase in the levels of hemolymph uric acid, urea, creatinine, glucose, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase. Their highest concentrations were observed in the Zn high-dose group and the field group, while the levels of total protein, albumin, and cholesterol showed a significant decrease among the tested groups as compared with the control group. Their determined lowest concentrations were in the Zn high-dose group and field group. Among tested groups, total hemocytes and granulated hemocytes decreased significantly while hyaline hemocytes increased as compared with the control group. Histological damages were observed in hepatopancreas, gills, and muscles in the field and Zn groups. The present study showed that exposure to Zn caused physiological and histological changes in Procambarus clarkia. We assumed that Procambarus clarkia could be used as a sensitive bioindicator for monitoring water quality criteria.

Microplastic contamination of fish gills and the assessment of both quality assurance and quality control during laboratory analyses.

Microplastic pollution has received substantial international attention in terrestrial and marine environments and in the atmosphere. In this study, we assessed microplastic pollution and analyzed the accumulation of microplastics in the gills of fish caught in the Zhoushan fishing ground from September 2017 to March 2018. The average abundance of microplastics was 0.49 ± 0.54 particles/gill and frequently found chemical polymers was polyethylene terephthalate. We also conducted experiments on microplastic pollution in the water and the working solutions used during the analytical process and found that the source of microplastic contamination was the solutions used. Moreover, we evaluated and scored experimental quality control and quality assurance adapted from the 'Total Accumulated Score' method. Valuable steps are recommended in order to produce reliable results and improve the quality of results in microplastic analyses.

Physiological assessment of fish health in mineral-rich areas of Ganjam, Odisha, India, and chronic toxicity of zirconium oxychloride on the fishes of Channa punctata.

The high concentration of metal toxicants in aquatic ecosystems has a detrimental impact on fish health that ultimately jeopardizes human health. Such threats mostly arise in mineral-rich areas where an increase in metal concentrations occurs in aquatic bodies due to anthropogenic activities like mining. The present study assessed the health of food fish Channa punctata from the mineral-rich areas of Ganjam, Odisha, India, mined for heavy and transition metal ores like ilmenite, zircon, monazite. The fishes collected from these areas showed histopathological anomalies in vital organs like the liver, kidney, gills, stomach and intestine while cytological analysis revealed vacuolated cytoplasm and micronuclei. Biochemical analysis showed a significantly lower lipid concentration in muscle (i.e., 0.177 ± 0.177 mg/gm) and liver (i.e., 0.169 ± 0.002 mg/gm) as compared to non-exposed fishes from adjoining non-mineral rich areas having a mean protein concentration of 87.48 ± 8.16 and 77.75 ± 0.892 mg/gm tissue in the muscle and liver, respectively, and a mean lipid concentration of 0.29 ± 0.009 mg/gm muscle and 0.34 ± 0.009 mg/gm liver. Chronic exposure to sublethal concentrations of zirconium oxychloride, a salt of zirconium, resulted in a significant decline in the concentration of protein, ranging from 57.5 ± 0.929 - 63.88 ± 1.95 mg/gm in muscle and 45.35 ± 2.332 - 51.98 ± 1.036 mg/gm in the liver. The lipid concentrations in muscle (0.03 ± 0.009 - 0.17 ± 0.009 mg/gm) and liver (0.06 ± 0.012 - 0.19 ± 0.007 mg/gm) were also significantly lower than the non-exposed fishes. Marked degenerative changes were identified in the histological sections of the gill, intestine, stomach, liver and kidney of zirconium oxychloride-treated fishes along with various nuclear deformities and micronucleus.

Toxicity assessment of organophosphorus in Ruditapes decussatus via physiological, chemical and biochemical determination: A case study with the compounds γ-oximo- and γ-amino-phosphonates and phosphine oxides.

Organophosphorus derivatives are widely used in human health care and have been detected in aquatic ecosystems. These compounds may pose significant risks to non-target exposed organisms and only limited studies are available on bioconcentration and the effects of organophosphorus derivatives on marine organisms. The aim of this work was to evaluate the possible toxic effects of two concentrations (20 and 40 µg/L) of γ-oximo- and γ-amino-phosphonates and phosphine oxides in mediterranean clams Ruditapes decussatus exposed for 14 days using different biomarkers and the changes of filtration and respiration rate. The use of clams in ecotoxicity evaluation is thus mandatory to assess the feasibility of assessing oxidative stress on R. decussatus after being exposed to γ-oximo- and γ-amino-phosphonates and phosphine oxides. The oxidative status was analyzed by measuring oxidative stress biomarkers RNS and ROS production in mitochondria, superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferases (GSTs), lipid peroxidation (LPO) and acetylcholinesterase (AChE), whose alteration was indicative of organophosphorus exposure, in both gills and digestive gland of the clams. No significant alterations in RNS, ROS production, SOD, CAT and AChE activities and MDA content were observed in both organs of clams treated with γ-oximophosphine oxides. It was possible then to hypothesize that γ-oximophosphine oxides may have probably exerted an incomplete alteration of antioxidant defenses and damage, which was changed by the activation of defense mechanisms. On the contrary, oxidative stress parameters were changed after exposure to γ-amino-phosphonates and phosphine oxides. In addition, metals accumulation, filtration and respiration rates were altered following exposure to all the studied organophosphorus compounds.

Sex-specific elemental accumulation and histopathology of pikeperch (Sander lucioperca) from Garasi reservoir (Serbia) with human health risk assessment.

Accumulation of 26 elements (Ag, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, and Zn) was analyzed in the gills, liver, and muscle of pikeperch males and females from Garasi reservoir using inductively coupled plasma optical emission spectrometry (ICP-OES). Histopathological (HP) changes in the gills and liver, and human health risk were also analyzed. The gills were most affected by metal pollution in both sexes. The concentrations of Hg in muscle tissue of four males, and Cd in two females and two males exceeded the maximum allowed concentrations. Statistical tests only revealed significant differences regarding the concentrations of Mg, K, and S in the muscle (higher in males) and Al, Ag, and Mn in the liver (higher in females) of individuals between sexes. Low to moderate levels of pathological changes were recorded for the gills and liver in both sexes. Significant differences between sexes were observed for inflammatory index of gills (IGI) and HP index of gills (IG), males had higher values compared to females, and for liver necrosis, where females had higher values compared to males. Gills were less affected by HP changes compared to the liver. There was no significant non-cancerogenic and cancerogenic health risk due to the consumption of pikeperch meat from the Garasi reservoir. However, women are under greater risk by consuming the meat of both male and female individuals, probably due to a longer lifetime and lesser body weight compared to the men.

Assessment of cytotoxicity in gills of fish Labeo rohita reared in untreated and treated sewage water.

The unregulated discharge of untreated municipal sewage water to the natural water bodies is a major threat to the aquatic ecosystems. In the present study, the fingerlings of Labeo rohita were exposed to treated sewage water and 1/10th of LC50 and 1/20th of LC50 of untreated sewage water (UT) obtained from sewage water treatment plant, Ludhiana, India. After determining 96-h LC50 value of UT, fingerlings were divided into four groups: control, treated, 1/10th of LC50 UT and 1/20th of LC50 UT and exposed for a period of 2 months. Our study revealed that 1/10th LC50 UT and 1/20th LC50 UT groups had significant reduction in body weight, total body length, standard body length and gills somatic index in comparison with the control and treated groups. Histopathological alterations in cellular structure of gills such as ruptured primary lamellae, broken secondary lamellae, distorted chloride cells and goblet cells, missing lamellae and disintegrated lamellar epithelium were also observed in 1/10th LC50 UT and 1/20th LC50 UT groups. A significantly high frequency of micronucleated (MN) cells was observed in 1/10th LC50 UT and 1/20th LC50 UT groups along with the presence of binucleated cells (BN), elongated nuclei (EN) and nuclear buds in gill cells. Genotoxic nature of UT was further confirmed from significantly high values of genetic damage index (GDI) and percentage (%) DNA damage in gill cells of fingerlings exposed to sub-lethal concentrations of UT. The study concluded that untreated sewage water has potential to induce anatomical and physiological defects in gills cells and the severity of toxicity increases with the increase in duration of exposure.

Characterization and spatial distribution of microplastics in two wild captured economic freshwater fish from north and west rivers of Guangdong province.

As a new type of pollutant, microplastics are of emerging widespread concern, while amount of research done in freshwater environments and organisms is litter compared to that in marine. Following this reality, the categories of MPs in two economic freshwater fish at 25 sites from 11 cities in the north and west rivers of Guangdong province were documented. Here, 76 individuals belong Oreochromis niloticus and Cirrhinus molitorella were investigated and microplastics were found in the GITs of 43.4% and gills of 25%. The average abundances of microplastics have significant difference between Oreochromis niloticus (0.015 items/ g) and Cirrhinus molitorella (0.031 items/g), while no difference by individual (~1.9 items). The plastics were dominated by white in color (61%), fragment in shape (67%), and lass than 1 mm in size (74%). The spatial distribution of microplastics revealed that there are significant differences between different cities in average abundances, and the highest average abundances of MPs were found in Zhanjiang city (4.25 items/individual) and Guangzhou city (0.044 items/g), respectively. Our results fully proved that the microplastics was widely ingested by wild fish species and suggested that the abundance and distribution of microplastics are positively related with the development of economy, tourism, industry, agriculture, and fishery.

Accumulation of trace elements in muscle, gill and liver of fish species (Capoeta umbla and Luciobarbus mystaceus) in the Tigris River (Turkey), and health risk assessment.

Two fish species (Capoeta umbla and Luciobarbus mystaceus) were collected from the Tigris River (Turkey), and tissues (gill, muscle and liver) of fish samples were analyzed for Cd, As, Mn, Cr, Cu, Co and Ni using the inductively coupled plasma-tandem mass spectrometry. Significant differences were present between fish species in regard to trace element (TE) concentrations in muscle for Mn, in liver for Cu, Cd and Mn, and in gill for As, Co, Cu and Cd (p < 0.05). Liver had the highest total TE concentration, followed by gill and muscle. Significant negative correlations were recorded between fish size (length and weight) and TE concentrations in the tissues. Both fish species showed no gender differences in TE accumulation in muscle, gill and liver (p > 0.05). The estimated daily intakes for all TEs were much lower than the tolerable daily intakes. The target hazard quotient (THQ) and total THQ values of all TEs did not exceed 1, which means that non-carcinogenic health effects are not expected for the consumers. Arsenic carcinogenic risk values were within acceptable range. Mean Cd concentrations in muscle tissue of both fish species exceeded the maximum permissible limit set by the European Commission Regulation, while mean concentrations of As, Cr and Cu were below the legislated limits.

Mercury in fish marketed in the Amazon Triple Frontier and Health Risk Assessment.

Fish has great socioeconomic, cultural, and nutritional importance for Amazonian populations. Despite all health benefits, fish can accumulate great amounts of mercury (Hg). The entry of Hg in aquatic trophic chains is an issue of concern to animal and human health. Higher risks of human exposure are strongly related to fish consumption. Upper Solimões population has one of the highest fish consumption rates of the Amazon. This study aimed to access the concentration of total Hg (THg) in muscle, liver, and gills of 17 species of fishes marketed in the Upper Solimões Region and Health Risk Assessment. Higher concentrations were observed in Carnivores/Piscivores. The highest THg concentration was found in liver of Cichla ocellaris (4.549 µg/g) and the lowest in gills of Hoplosternum littorale (0.002 µg/g). Most species had higher THg concentrations in muscle>liver>gills, in the Ebb period, and liver>muscle>gills, in the Flood period. Hoplias malabaricus, Pseudoplatystoma fasciatum, Plagioscion squamosissimus, Ageneiosus inermis, and C. ocellaris presented average THg concentrations above the safe limit stablished by WHO. THg levels in C. ocellaris, H. malabaricus, P. squamosissimus, P. fasciatum, and Semaprochilodus insignis were higher than those found in fish of heavily impacted areas. Signs of bioaccumulation and biomagnifications of Hg can already be observed in this region. The Western Amazon Region urgently needs government actions to inhibit Hg release in aquatic ecosystems and to advise this population on the safe amount of fish to be eaten according to species and period of the year.

Bioavailability Assessment of Metals in Freshwater Environments: A Historical Review.

Many metals (aluminum, cadmium, cobalt, copper, nickel, lead, zinc) are widely studied environmental contaminants because of their ubiquity, potential toxicity to aquatic life, and tendency for toxicity to vary widely as a function of water chemistry. The interactions between metal and water chemistry influence metal "bioavailability," an index of the rate and extent to which the metal reaches the site of toxic action. The implications of metal bioavailability for ecological risk assessment are large, with as much as a 100-fold variability across a range of water chemistries in surface waters. Beginning as early as the 1930s, considerable research effort was expended toward documenting and understanding metal bioavailability as a function of total and dissolved metal, water hardness, natural organic matter, pH, and other water characteristics. The understanding of these factors and improvements in both analytical and computational chemistry led to the development of modeling approaches intended to describe and predict the relationship between water chemistry and metal toxicity, including the free ion activity model, the gill surface interaction model, the biotic ligand model, and additional derivatives and regression models that arose from similar knowledge. The arc of these scientific advances can also be traced through the evolution of the US Environmental Protection Agency's ambient water quality criteria over the last 50 yr, from guidance in the "Green Book" (1968) to metal-specific criteria produced in the last decade. Through time, water quality criteria in many jurisdictions have incorporated increasingly sophisticated means of addressing metal bioavailability. The present review discusses the history of scientific understanding of metal bioavailability and the development and application of models to incorporate this knowledge into regulatory practice. Environ Toxicol Chem 2019;39:48-59. © 2019 SETAC.

Assessment of the heavy metal accumulation in the Blue Swimmer Crab (Portunus pelagicus), northern Bay of Bengal: Role of salinity.

This is the first report to assay the heavy metal accumulation in Blue Swimmer Crab in the northern Bay of Bengal. The present study finds that copper (Cu) concentration though has been the highest compared to the other metals, particularly in the gill. Cadmium (Cd) and lead (Pb) have high affinity to be concentrated in Hepatopancreas all through the year. All the metal concentrations were higher during monsoon season (comparatively low salinity) than non-monsoon (high salinity) in the different body parts of Blue swimmer crab i.e. the inverse relationship between accumulation of heavy metals and sea water salinity has been shown. Present study revealed that salinity having the role to accumulate metal in different body parts of Blue Swimmer Crab. In future, microcosm experiments should be done to test the effect of frequent fluctuations of ambient salinity, such as is usual in different seasons in the present study area.

Distribution and health risk assessment of cadmium, lead, and mercury in freshwater fish from the right bank of Senegal River in Mauritania.

Clarias gariepinus (African catfish) and Oreochromis niloticus (Tilapia fish) from the right North bank of the Senegal River in Mauritania (Rosso, Boghé, and Kaédi) were sampled during 1-year monitoring and tested for lead (Pb), cadmium (Cd), and mercury (Hg) levels. Fishing from the Senegal River is an essential source of food for the local population and these two species are the most common. Muscle presents higher Hg concentrations than liver and gills for both species. Gill Hg concentrations from Kaédi are higher than Boghé and Rosso for both species. The Cd levels measured in gills were low in the different locations and revealed high variation throughout the 1-year study. No significant differences were observed between concentrations of Cd in Clarias gariepinus and Oreochromis niloticus parts. Statistical treatment did not show a considerable variation of Pb concentration between the different parts, revealing lower levels in gills from Boghé than the ones from Kaédi and Rosso. The associated human health risk was calculated from the concentration levels using the target hazard quotient (THQ) approach. Even though all the THQ values and the hazard index were lower than 1 for the determined trace metals when the exposure frequency was not greater than three times a week, eating frequency in the studied locations sometimes is greater than five, thus posing a health risk, especially at Kaédi and Boghé.

Mass mortality of fish and water quality assessment in the tropical Adyar estuary, South India.

Mass mortality of fishes was reported at the Adyar estuary, South India, during November 2017. The probable reasons for fish mortality are analyzed in this paper. Critical assessments on water quality parameters including the metal concentrations, nutrients, and histology of gills and liver of fish (Mugil cephalus) isolated from the impact zone were performed. Among the metals observed, chromium showed levels (3.64 ± 0.001 mg L-1) much above the average permissible limits (0.1 mg L-1). The measured values of physico-chemical parameters in the impact zone are as follows: dissolved oxygen 4.7 ± 0.22 mg L-1, total alkalinity 132 ± 4 CaCO3 mg L-1, salinity 5.3 ± 0.3 PSU, temperature 27.8 ± 0.16 °C, nitrate, 1.66 ± 0.48 mg L-1, nitrite 0.01 ± 0.0008 mg L-1, ammonia 0.03 ± 0.001 mg L-1, phosphate 1.52 ± 0.002 mg L-1, and silicate 13.85 ± 3.1 mg L-1. The low salinity could have escalated the toxicity of the metal. In addition, histology of gills and liver showed cellular necrosis, epithelial lifting, hyperplasia, edema, mucous cell proliferation in the gills, cytoplasmic vacuolation of hepatocytes, and degeneration of liver which reveal that chromium toxicity is the most probable cause for mass mortality.

Metals in wild fish from Gaotang Lake in the area of coal mining, China: assessment of the risk to human health.

Environmental pollution can cause metal accumulation in aquatic organisms, but information on metal bioaccumulation in wild fish from coal mining areas is limited. We investigated tissue-specific metal accumulation in six economically important fish species common to Gaotang Lake, China, located in a coal mining area. We also conducted an assessment of potential risks to human health from consumption of these fish. Mean concentrations of arsenic, cadmium, cobalt, copper, mercury, lead, and antimony in the muscle of six fish species were below the corresponding Chinese maximum allowable concentrations except chromium and generally comparable with levels in fish reported by other studies. Tissue distribution patterns suggested that chromium and mercury were easily transported to the muscle, but concentrations of the other six metals were higher in the liver and gills. The daily intake of each metal was estimated at 0.002-0.220 g/day/kg body weight, and the non-carcinogenic health risks associated with the consumption of the fish from Gaotang Lake were acceptable. The results suggest that metal bioaccumulation in wild fish is not high in this coal mining area.

Trace metal distribution in crab organs and human health risk assessment on consumption of crabs collected from coastal water of South East coast of India.

The concentrations of nine heavy metals accumulated in different organs of two crab species collected from the South East coast of India were estimated. The order of trace metal concentration in different organs of Portunus pelagicus was Cu > Mn > Cd > Ni > Pb > Co > Hg = Cr = U in gills, Cu > Mn > Cd > Ni > Pb = Co > Hg > Cr = U in hepatopancreas, and Cu > Cr > Ni > Mn > Cd > Pb > Co > Hg > U in muscles, whereas that for Portunus sanguinolentus was Cu > Mn > Cd > Ni > Pb > Co > Hg > Cr = U in gills, Cu > Mn > Cd > Ni > Pb = Co > U > Cr = Hg in hepatopancreas, and Cr > Cu > Ni > Mn > Cd > Co > Pb > Hg = U in muscles. The order of trace metal uptake for different organs was gills > hepatopancreas > muscles. Individual mean bioaccumulation index (IMBI) values varied between 0.0 and 0.52, 0.0 and 0.28, and 0.06 and 0.30 for gills, hepatopancreas, and muscles, respectively. Cr in muscles of P. sanguinolentus and Cu and Cd in all organs of both the species were found to be higher than the maximum permitted concentration recommended by food safety guidelines. Target hazard quotient (THQ) results suggested that there is a potential risk due to Co, Cd, and Cr, particularly for children, if the crab consumption frequency is more than once a month.

Assessment of pollution biomarker and stable isotope data in Mytilus galloprovincialis tissues.

Superoxide dismutase (SOD) is one of the antioxidant defense enzymes in mussels and converts the superoxide anion into hydrogen peroxide and this enzyme is used as biomarkers of oxidative damage. As well as many topics in ecology, stable isotopes are also signature for organic and heavy metal pollution in aquatic ecosystems. This study aims to compare the stable carbon and nitrogen values of different mussel tissues and the changes on the SOD values of the same tissues in order to understand the relationship between two mechanisms of bioindicator processes of physiological response of mussel to pollution. The changes in SOD activity in the gill, hepatopancreas, and mantle tissues of Mytilus galloprovincialis with δ13C and δ15N isotopes were assessed in two locations (Kepez and Güzelyali) in Çanakkale. The SOD values of mussel samples were found as the gill > hepatopancreas > mantle collected from Kepez and the gill > hepatopancreas collected from Güzelyali. There were no significant differences among the mean SOD values of different tissues. There was enrichment both in nitrogen and carbon isotope values of hepatopancreas tissues both in Kepez and Güzelyali samples. There was a negative correlation between both isotope values and SOD values of samples. As well as SOD values, the isotopic composition of particularly hepatopancreas tissue is a good indicator for evaluation of pollution.

An assessment of the ability to ingest and excrete microplastics by filter-feeders: A case study with the Mediterranean mussel.

Plastic debris has been recognized as a growing threat to marine biota due to its widespread distribution and possible interactions with marine species. Concerns over the effects of plastic polymers in marine ecosystems is reflected in the high number of toxicological studies, regarding microplastics (<5 mm) and marine fauna. Although several studies reported that organisms ingest and subsequently eliminate microplastics (MP), the potential effects at organ and tissue level remain unclear, especially considering exposure to different microplastic sizes and concentrations. The present study aimed at investigating potential pathophysiological effects of the ingestion of MP by marine filter-feeders. For the purpose, Mediterranean mussel (Mytilus galloprovincialis) was exposed to spherical polystyrene MP (2 and 10 µm Ø) over short- and medium-term exposure periods, under single and combined concentrations that represent high, yet realistic doses (10 and 1000 MP mL-1). Overall, results suggest rapid MP' clearance from water column by filtering, regardless of MP size. Ingestion occurred, identified by MP in the lumen of the gut (mostly in midgut region), followed by excretion through faeces. However, no MP were found in gills or digestive gland diverticula. Biochemical indicators for oxidative stress were generally irresponsive regardless of organ and time of exposure. Small foci of haemocytic infiltration in gastric epithelia were found, albeit not clearly related to MP ingestion. Globally, no evident histopathological damage was recorded in whole-body sections of exposed animals. The present findings highlight the adaptative ability of filter-feeding bivalves to cope with filtration of suspended MP, resulting in rapid elimination and reduced internal damage following ingestion of spherical MP. Nevertheless, the fact that the animals are able to translocate MP to the gut reveals that filter feeding organisms may indeed became a target of concern for fragmented materials with smaller, mixed sizes and sharper edges.

Baseline assessment of heavy metals content and trophic position of the invasive blue swimming crab Portunus segnis (Forskål, 1775) in the Gulf of Gabès (Tunisia).

This study provides a baseline assessment of cadmium, copper, iron, manganese, lead, and zinc concentrations in muscles, gills, and exoskeleton of the Lessepsian blue swimming crab Portunus segnis captured in the Gulf of Gabès (Southern Mediterranean Sea, Tunisia) in November 2015. Furthermore, the species' trophic position is estimated using CN stable isotope analysis. The exoskeleton showed the lowest metal contents; in soft tissues, the essential Cu, Fe, and Zn and the non-essential Cd, Mn, and Pb showed the highest and lowest concentrations, respectively. The crab was characterized by a trophic position of 3.32, confirming its carnivorous trophic habits. Compared with literature data on invertebrate and fish species from the same area, Cd and Pb resulted remarkably low in the crab's soft tissues, while a food web-scale dilution effect was indicated. The need of a comprehensive assessment of the ecological impact of Portunus segnis in invaded Mediterranean waters is discussed.