Assessment of carbamazepine acute toxicity in the cockle Cerastoderma edule through chemical, physiological and biochemical tools

The cockle Cerastoderma edule was exposed to four concentrations (5, 10, 20 and 70 μg L-1) of carbamazepine (CBZ). This anticonvulsant was found to alter the mussel behavior of by reducing its clearance rate (CR). Analysis of CBZ accumulation in tissues of C. edule was carried out using HPLC-UV after 48 or 96 hours of exposure. In addition, an overproduction of H2O2 by the bivalves was detected following exposure to CBZ but nitrite levels remained unchanged. Moreover, superoxide dismutase and catalase activities showed a significant increase in relation to their contact with CBZ. The activity of the biotransformation enzyme gluthatione-S-transferase did not change during exposure. Malondialdehyde (MDA) levels indicating cellular damage, increased when bivalves were exposed to 20 and 70 μg l-1 of carbamazepine for 96 h CBZ. The results also indicate that acetylcholinesterase activity (AChE) was inhibited in all CBZ concentrations during the 48 h exposure period. However, during the 96 h exposure period, AChE was only inhibited at the highest concentration. Further studies are needed now for more exploration of the toxicity of CBZ since it could be bioaccumulable throughout the food web and may affect non-target organisms.

Effects of permethrin on biomarkers in Mediterranean clams (Ruditapes decussatus)

The present study was focused on the assessment of Catalase (CAT) and Acetylcholinesterase (AChE) activities in Mediterranean clams (Ruditapes decussatus) exposed to 50, 100 and 150 μg/L of Permethrin for 5, 10, 15, 20 and 25 days. In water, the measured concentrations of Permethrin in the treated aquariums were respectively 16.66, 38.24 and 55.61 μg/L. Results showed that CAT activity was increased after 5 days of exposure to high concentration reaching maximum value of 10.14 μmol/min/mg proteins after 25 days. However, no significant changes in AChE activity after 5 days of exposure were detected in all treated groups. AChE activity was significantly inhibited after 10 days with 100 and 150 μg/L and still depending on concentration and time. Maximum inhibition of AChE activity was reached after 25 days with the highest concentration of Permethrin. Our data indicated that exposure to Permethrin modifies biomarker profiles inducing oxidative stress and reducing AChE activity in Mediterranean clams.

Characterization of aerobic polycyclic aromatic hydrocarbon-degrading bacteria from Bizerte lagoon sediments, Tunisia

AIMS

To characterize polycyclic aromatic hydrocarbon (PAH)-degrading bacteria from sediments of the Bizerte lagoon, and to determine their ability to resist other pollutants such as antibiotics and heavy metals.

METHODS AND RESULTS

More than 100 strains were isolated for their ability to use fluoranthene as the sole carbon and energy source. Most of them showed antibiotic and heavy metal resistance; 20 representative strains were selected for further analysis. 16S rRNA coding sequences analysis showed that the majority of the selected bacteria (75%) were affiliated to the Gammaproteobacteria. The selected strains also utilized high molecular weight PAHs containing up to four benzene rings and showed different profiles of PAH substrate usage suggesting different PAH degradation pathways. These results are consistent with the fact that nah-like genes and idoA-like genes, involved in PAH degradation, were detected in 6 and 1 strains respectively.

CONCLUSIONS

The Bizerte lagoon, polluted by many human activities, leads to the co-selection of strains able to cope with multiple contaminants.

SIGNIFICANCE AND IMPACT OF THE STUDY

Polluted areas are often characterized by the concomitant presence of organic pollutants, heavy metals and antibiotics. This study is one of the first showing bacterial strains adapted to multiple contaminants, a promising potential for the development of bioremediation processes.

Responses of Hexaplex (Murex) trunculus to selected pollutants

Cadmium, copper and zinc concentrations (in whole soft body and in tissues) were measured in Hexaplex trunculus collected from the Bizerta lagoon in Tunisia. An evaluation of the biological effects of the most toxic metals (cadmium and copper) and of two organics (carbofuran and lindane), present in the sediments of the Bizerta lagoon, was attempted by measuring biomarkers (acetylcholinesterase: AChE, catalase: CAT and glutathione S-transferase: GST activities) in animals experimentally exposed for 48 or 72 h. The concentration ranges as follows: Zn>Cu>Cd. Copper concentrations are highly variable (8.0 to 235 microg g(-1) d.w.) whereas cadmium (range 1.35-4.86 microg g(-1)) and zinc (range 360-1320 microg g(-1)) concentrations are less variable. The digestive gland and the gill take up more metal than the muscle. AChE activity in H. trunculus is decreased by exposure to carbofuran or the mixture carbofuran and cadmium, in the digestive gland and muscle and by copper and by lindane in the digestive gland. AChE is generally inhibited by carbamates but some other compounds may also decrease this activity as observed in this paper. An increase in CAT activity associated with a decrease in GST activity is noted in the muscle of H. trunculus exposed to cadmium, to carbofuran and to the mixture of cadmium and carbofuran, and in the digestive gland of animals exposed to lindane. These pollutants may act upon glutathione and decrease the GST activity that cannot detoxify them and CAT activity has a protective effect. On the contrary, copper increases CAT and GST activities in the digestive gland of exposed gastropods; these enzymes seem to cooperate and play together their rôle of anti-oxidant enzymes. If H. trunculus is not a bioindicator species for metal concentrations, due to a high variability in metal concentrations, nevertheless the biochemical responses to pollutants (cadmium, copper, carbofuran and lindane) represented by AChE, CAT and GST activities may act as biomarkers of exposure in this species.

The use of acetylcholinesterase activity in Ruditapes decussatus and Mytilus galloprovincialis in the biomonitoring of Bizerta lagoon

The variations of acetylcholinesterase activity, considered to be a biochemical biomarker of organophosphorus and carbamate compounds, was followed in Mediterranean clams (Ruditapes decussatus) and mussels (Mytilus galloprovincialis) as a function of season and sampling sites in the lagoon of Bizerta (Tunisia). Results show that acetylcholinesterase activity in clams collected from station A was the lowest and was so throughout the year. This low activity may be due to the input of non-treated waste waters in the lagoon. Heavy metal contamination has been reported in the sediments of this area, suggesting that acetylcholinesterase activity in clams may be inhibited by this type of pollution. Clams harvested from station F, a site adjacent to an agricultural area, were characterized by a decrease in acetylcholinesterase activity, especially after rain periods. Clams from station J presented the highest activity throughout the greater part of the year. This phenomenon may imply that this location is less affected by pollutants inhibiting AChE activity than the others. In the mussels from station C, located in the channel from the lagoon to the Mediterranean and submitted to pollutants (urban wastes from Bizerta and hydrocarbons from the maritime traffic), acetylcholinesterase activities were lower than in those from station J. In conclusion, the variations in acetylcholinesterase activity observed between stations in both species may be the result of pollution and of the environmental conditions.