Seasonal variation of oxidative stress biomarkers in clams Ruditapes decussatus sampled from Tunisian coastal areas

Seven (7) sites from to the Tunisian coastal area were monitored through four seasons using several oxidative stress biomarkers including lipid peroxidation. Catalase (CAT) specific activity was determined in clam Ruditapes decussatus digestive gland. Lipid peroxidation was assessed in the same tissues using malondialdehyde (MDA) concentration, neutral lipid (NL) and lipofuscin accumulation. Results show that catalase specific activity varies between sites and fluctuates in time. The highest CAT activities were recorded in sites from Bizerta Lagoon and sites neighbouring Sfax city. Malondialdehyde accumulation in digestive gland cells seems to be very pronounced in animals sampled in summer and autumn. Digestive gland sections of clams sampled from reported heavy metal polluted sites exhibited higher volume density of residual bodies. Our results showed that the neutral lipids and lipofuscin content in clam's digestive gland are more sensitive to general stress as compared to other biomarkers, and could be used successfully in clams as early warning tools in field biomonitoring programs.     

Integrated assessment of biochemical responses in Mediterranean crab (Carcinus maenas) collected from Monastir Bay, Tunisia

The biochemical response of Mediteranean Crab (Carcinus maenas) collected at five stations of Monastir Bay and from Kuriat station as control was studied using a set of complementary biomarkers. The catalase, glutathione S-transferase, lactate dehydrogenase, acetycholinesterase activities; and metallothionein and malonediladehyde levels in gills were evaluated. Results revealed differences among sites in relation to each specific biomarker. Hence, a suite of biomarkers can be used to discriminate sampling sites according to types of pollution, reflecting differing conditions of anthropogenic impact. Based on Integrated Biomarker Response, the highest values and critical biochemical alteration were observed at Khniss and Ksibat in response to urban and industrial discharges and the lowest IBR value was found at reference site. The current study has shown clearly that a biomarker-based index is usefulness tool in the monitoring Tunisian coast using C. maenas as sentinel specie. Further studies in progress to investigate the seasonal variations of IBR levels and its relationship to pollutants concentrations in the sediment, gills and digestive gland of Carcinus maenas from Monastir Bay.     

Multimarker approach analysis in common carp Cyprinus carpio sampled from three freshwater sites

The aim of this study is to assess the response of a multimarker approach in common carp Cyprinus carpio sampled from three Tunisian dam lakes selected according to different environmental and ecological characteristics. Glutathione-S-transferase (GST) activity was analyzed in carp liver and used as a phase II detoxification enzyme, hepatic metallothionein content (MTs) was used as a metallic stress indicator, and cholinesterase activities were analyzed in muscle and brain and used as neurotoxicity biomarker. Micronucleus frequency test (MN) as a genotoxicity marker. GST and MT levels showed an increase in fish from the Bir Mcherga site and a decrease in Sidi Saâd site with respect to fish from Nebhana site. Results showed a strong inhibition of cholinesterase activities in fish from Bir Mcherga and Sidi Saâd sites compared to Nebhana site. Relatively high level of MN is reported specially in fish blood from the Bir Mcherga site.     

Biochemical effects in crabs (Carcinus maenas) and contamination levels in the Bizerta Lagoon: an integrated approach in biomonitoring of marine complex pollution

The biochemical effects in Carcinus maenas and contamination levels in seawater and sediments of Bizerta Lagoon (northeast of Tunisia) were investigated. The levels of metals and hydrocarbons were higher in seawater and sediments in Menzel Bourguiba and Cimentery in February and July than in the other sampling sites. Differences among sites for glutathione S-transferase, catalase, acetylcholinesterase activities, and the content of lipid peroxidation and metallothioneins in two important organs which accumulated contaminants (the gills and the digestive gland) of the C. maenas were found and possibly related to differences in metal and hydrocarbon levels. The seasonal variation of biomarkers was possibly associated with chemical contamination and also with the high fluctuation of physico-chemical characteristics of the sites. The integrated biomarker response values found in the five sites is in good agreement with hydrocarbon and trace metal concentrations detected in the water and sediments of the stressful places where crabs are living.     

Electrostatic precipitation in atmospheric aerosols

The use of electrostatic force mechanisms can make a substantial contribution to control the pollution from air solids arising naturally, or from human development. In the present investigation we discuss the efficiency of a technique to precipitate the atmospheric aerosol of a size <5 µm, by energizing metal mesh (Por=0.7) collectors (+, N, and –) using low D.C. voltage (0–30 V or –1.224×10² Vm^–1).