Heavy Metal Bioaccumulation and Oxidative Stress Profile in Brachidontes pharaonis (Bivalvia: Mytilidae) from the Tunisian Coast: Insight into Its Relevance as Bioindicator of Marine Pollution.

This study aims to verify the relevance of Brachidontes pharaonis to assess the ecotoxicological status of polluted sites. For this, the levels of some heavy metals (i.e. Zn, Cu, Pb, and Cd) and a battery of biomarkers including metallothionein (MT), malondialdehyde (MDA), reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) were assessed in mussels collected from the harbor of Rades (North), and the harbor of Zarzis (South). Moreover, abiotic parameters including temperature, salinity, pH, and dissolved oxygen were assessed. Results from the ICP-OES showed that the southern population exhibited a higher metal pollution index with significantly higher Zn, Cu, and Pb concentrations. Moreover, the specimens from Zarzis displayed significantly higher levels of MDA, MT, GSH, GPx, SOD, and CAT reflecting higher levels of oxidative and chemical stress. These results emphasize the potential utility of B. pharaonis for the monitoring of heavily impacted sites.

Impacts of engineered iron nanoparticles on oxidative stress, fatty acid composition, and histo-architecture of the smooth scallop Flexopecten glaber.

Engineered iron nanoparticles are widely used in environmental remediation, yet their potential toxic effects on marine biota remain poorly elucidated. This study aimed to gain insight into the nanoscale zero-valent iron (NZVI) toxicity mechanisms for marine invertebrates. Aside from the effect on oxidative status and histopathology, the effect of NZVI on lipid metabolism in bivalves was studied for the first time. To this end, specimens of Flexopecten glaber were exposed to ascending concentrations (0.5, 1, and 1.5 mg/L) of NZVI for 96 h. Results illustrate differential patterns of iron accumulation in the gills and the digestive gland. By increasing NZVI concentrations, the total iron level tended to markedly increase in the gills and decrease in the digestive gland, reaching 132 and 37.6 µg/g DW, respectively, in the specimens exposed to 1.5 mg/L. Biochemical and cellular biomarkers highlighted that NZVI caused oxidative stress (measured as hydrogen peroxide, malondialdehyde, and advanced oxidation protein product levels) and alterations of antioxidant defense systems, including reduced glutathione, non-protein thiol, glutathione peroxidase, superoxide dismutase, and catalase. Modulation of lipid metabolism with changed fatty acid compositions (mainly an increase in the saturation and a decrease in unsaturation levels) was also observed in both gills and digestive gland. Moreover, several histological damages, including lipofuscin accumulation, infiltrative inflammations, and digestive tubule alterations, were observed in the two studied organs, providing supplementary evidence regarding the toxic effect of NZVI. This study adds to the growing body of evidence pointing to the hazardous impacts of iron NPs on aquatic ecosystems.

Glyphosate exposure modulates lipid composition, histo-architecture and oxidative stress status and induces neurotoxicity in the smooth scallop Flexopecten glaber.

Glyphosate is the most sprayed pesticide across the globe. Its toxicity to non-target marine organisms has recently piqued the scientific community's interest. Therefore, the purpose of this study is to investigate the potentially toxic effects of glyphosate on scallops, an ecologically and economically important bivalve group. To do that, specimens of the smooth scallop Flexopecten glaber were exposed to different concentrations (10, 100, and 1000 µg L-1) of the technical-grade glyphosate acid (GLY) for 96 h. The detrimental effects of this pollutant were assayed at cellular and tissular levels. The obtained results showed that the GLY was able to induce oxidative stress in the gills and the digestive gland of F. glaber as revealed by the enhanced hydrogen peroxide (H2O2), protein carbonyls (PCO), malondialdehyde (MDA), and lipid peroxides (LOOH) levels and the altered antioxidant defense system (the glutathione GSH content and the superoxide dismutase (SOD) activity). Additionally, GLY was found to alter the fatty acid profile, to exert a neurotoxic effect through the inhibition of the acetylcholinesterase (AChE) activity, and to provoke several histopathological damages in the two organs studied. The obtained results revealed that the pure form of GLY may exert toxic effects on F. glaber even at relatively low concentrations.

Acute toxicity and teratogenicity of carbaryl (carbamates), tebufenpyrad (pyrazoles), cypermethrin and permethrin (pyrethroids) on the European sea bass (Dicentrarchus labrax L, 1758) early life stages.

The toxicity of carbaryl, tebufenpyrad, cypermethrin and permethrin was evaluated in European sea bass Dicentrarchus labrax during the embryonic and larval development using six different concentrations per chemical. The order of the toxicity effectiveness was carbaryl > tebufenpyrad > cypermethrin > permethrin. The larvae were more sensitive to all tested chemicals than embryos. The LC50 of carbaryl, tebufenpyrad, cypermethrin and permethrin was determined as 13.88, 43.96, 92 and 142 ppm and 9.27, 25.67, 48.4 and 72.7 ppm in embryo and larvae, respectively. Furthermore, the tested pesticides exhibited teratogenic effects on D. labrax embryo-larval stages. The observed malformations were coagulation, no spherical egg, unhatched egg, pericardial oedemata, yolk oedemata, lordosis, kyphosis, scoliosis, no eye, cranial deformation and body atrophy. Malformations were induced with 0.5 ppm carbaryl, 10 ppm tebufenpyrad and 50 ppm cypermethrin and permethrin; the highest rates of malformation were noted with 16 ppm carbaryl, 160 ppm tebufenpyrad, 400 ppm cypermethrin and 400 ppm permethrin as 34.5%, 28%, 17.5% and 16%, respectively. A positive correlation between the incidence of malformation and the increase of pesticide concentration was established.

Assessment of the heavy metal levels and biomarker responses in the smooth scallop Flexopecten glaber from a heavily urbanized Mediterranean lagoon (Bizerte lagoon).

Marine heavy metal pollution is a worldwide serious issue. Like almost all Mediterranean lagoons, the Bizerte lagoon is highly urbanized and suffers from intensive anthropogenic pressure. In the present study, we screened the metal contamination and biomarker responses in the smooth scallop Flexopecten glaber inhabiting this vulnerable ecosystem. To this end, the concentrations of six heavy metals (HM) (i.e., Cu, Pb, Zn, Cd, Hg, and Fe) and a panel of biochemical endpoints including malondialdehyde (MDA), metallothioneins (MT), reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) were determined in the gills and digestive gland across seasons (warm and cold) and sites (S1 and S2). The distribution of almost all analyzed metals in F. glaber tissues varied significantly between sites, seasons, and organs. The highest levels were recorded at S2 during the warm period. Moreover, the digestive gland was found to accumulate greater concentrations of HM than the gills. Marked spatio-temporal variations were also observed for oxidative stress biomarkers, mainly in the gills, while the digestive gland seems to be rather sensitive to seasonal variability. Particularly, we noticed that among the used biomarkers, MT did not show significant variations in the two tested organs across seasons and sites. From the obtained results, F. glaber appears as a sensitive organism to anthropogenic metal contamination and can be proposed as a promising bioindicator species for marine pollution.

Azithromycin effects on the European sea bass (Dicentrarchus labrax) early life stages following acute and chronic exposure: Laboratory bioassays.

The purpose of this study was to assess the acute and chronic effects of the macrolide azithromycin (AZI) on the European sea bass (Dicentrarchus labrax) early life stages. Azithromycin is a semi-synthetic antibiotic frequently detected in the aquatic environment, despite this few information about its effects on aquatic organisms were reported. Investigations of AZI acute toxicity on D. labrax early life stages were made using six increasing concentrations (0.625, 1.25, 2.5, 5, 10 and 20 mg/l) during 96 h of exposure. The chronic toxicity was tested at one year old juveniles using two sublethal concentrations (C1 = 0.05 µg/l and C2 = 0.8 µg/l) during 4 and 14 days. Malondialdehyde (MDA), glutathione S-transferase (GST), catalase (CAT) and acetylcholinesterase (AChE) activities were measured in gill and liver tissues of juveniles. The half lethal concentration (LC50), 96 h value of AZI for the European sea bass was determined as 31 mg/l. Results showed that short-time exposure to 20 mg/l of azithromycin induces 18% and 7.5% of larvae mortality and morphological abnormalities, respectively. Azithromycin provoked oxidative stress, peroxidative damage, and neurotoxicity in juveniles D. labrax. Overall, the CAT and AChE activities decreased in gill and liver tissues, while dissimilarity in response in both organs depending on AZI concentrations and time of exposure was observed in MDA and GST levels.

The detoxifying effect of Polygonum equisetiforme extracts against dichlorvos (DDVP)-induced oxidative stress and neurotoxicity in the commercial clam Ruditapes decussatus.

Effects of Polygonum equisetiforme extracts against dichlorvos were investigated in the commercial clam Ruditapes decussatus. The toxicity of this pesticide was firstly tested in R. decussatus gill and digestive gland tissues using five doses varying from 0.05 to 1 mg/l during 2, 4, and 7 days. Results showed that 0.05 mg/l of DDVP induced oxidative stress and neurotoxicity in R. decussatus after 2 days of exposure. Investigations of the effects of P. equisetiforme extracts in R. decussatus exposed to 0.25 mg/l of DDVP were made in clams receiving three concentrations (0.009, 0.045, and 0.09 g/l) during 4 and 7 days. Antioxidant enzymes SOD and CAT as well as H2O2 content and AChE were quantified by colorimetric method. Four days of exposure to DDVP increased SOD and CAT activities and enhances H2O2 content. AChE levels decreased considerably following DDVP exposure, although a restoration in the enzyme activity was observed with P. equisetiforme extract (E3 = 0.09 g/l). Overall, P. equisetiforme extract at concentration (E1 = 0.009 g/l) prevents oxidative stress caused by DDVP, while 0.09 g/l of P. equisetiforme extract induced an effect similar to that obtained with DDVP alone. Nevertheless, this concentration was found effective for the restoration of the AChE activity.

Ecological risk assessment of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in marine environment using Isochrysis galbana, Paracentrotus lividus, Siriella armata and Psetta maxima.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are anthropogenic substances classified as persistent bioaccumulative compounds and are found in various environmental compartments throughout the world, from industrialized regions to remote zones far from areas of production. In this study, we assessed the effects of PFOA and PFOS on early life stages of marine test species belonging to three different trophic levels: one microalga (Isochrysis galbana), a primary consumer (Paracentrotus lividus) and two secondary consumers (Siriella armata and Psetta maxima). Acute EC(50) values for PFOS were 0.11 mg L(-1) in P. maxima, 6.9 mg L(-1) in S. armata, 20 mg L(-1) in P. lividus and 37.5 mg L(-1) in I. galbana. In the case of PFOA, the toxicity was lower but the ranking was the same; 11.9 mg L(-1) in P. maxima, 15.5 mg L(-1) in S. armata, 110 mg L(-1) in P. lividus and 163.6 mg L(-1) in I. galbana. The Predicted No Effect Concentration (PNEC) for PFOS and PFOA in marine water derived from these acute toxicity values are 1.1 µg L(-1) for PFOS and 119 µg L(-1) for PFOA. This study established a baseline dataset of toxicity of PFOS and PFOA on saltwater organisms. The data obtained suggest that PFOA pose a minor risk to these organisms through direct exposure. In the perspective of risk assessment, early life stage (ELS) endpoints provide rapid, cost-effective and ecologically relevant information, and links should be sought between these short-term tests and effects of long-term exposures in more realistic scenarios.

Acute toxicity of polybrominated diphenyl ethers (PBDEs) for turbot (Psetta maxima) early life stages (ELS).

BACKGROUND, AIM AND SCOPE: The environmental presence of polybrominated diphenyl ethers (PBDEs), among which BDE-47 and BDE-99 are particularly abundant, makes toxicity data necessary to assess the hazard risk posed by PBDE to aquatic organisms. This study examines the effects of BDE-47 and BDE-99 on embryo-larval stages of the marine flatfish turbot. MATERIALS AND METHODS: The turbot embryos were exposed at nominal concentrations of BDE-47 and BDE-99 for 6 days. Selected dose levels were relevant for investigating sublethal and lethal effects. RESULTS: Both tested compounds caused lethal toxicity as well as non-lethal malformations during embryo development. We found a high toxic potency of BDE-47 compared to BDE-99 (LC50 values for embryos and larvae, respectively, BDE-47: 27.35 and 14.13 µg L⁻¹; BDE-99: 38.28 and 29.64 µg L⁻¹). DISCUSSION: The present study shows high sensitivity of fish early life stages (ELS) to PBDE compounds. Based on environmental concentrations of dissolved PBDEs from various aquatic ecosystems, waterborne BDE-47 and BDE-99 pose little risk of acute toxicity to marine fish at relevant environmental concentrations. CONCLUSIONS: Turbot fish ELS proved to be an excellent model for the study of ecotoxicity of contaminants in seawater. The results demonstrate harmful effects of PBDE on turbot ELS at concentrations in the range of parts per billion units. RECOMMENDATIONS AND PERSPECTIVES: In the perspective of risk assessment, ELS endpoints provide rapid, cost-effective and ecologically relevant information, and links should be sought between these short-term tests and effects of long-term exposures in more realistic scenarios.