Multiple biomarkers of pollution effects in Solea solea fish on the Tunisia coastline

This field study investigates the morphological indices (condition index, hepatosomatic index) and biochemical (catalase (CAT), glutathione S-transferase (GST), acetylcholinesterase (AChE), metallothionein (MT), lipid peroxidation) parameters in liver, gills and kidney of common sole (Solea solea) originating from different sites of the Tunisian coast area impacted by different anthropogenic activities. Differences among sites and tissues for AChE, GST, CAT, MT and TBARS were found and possibly related to known sources of domestic and industrial discharges in the studied sites. Liver, gills and kidney CAT, liver and kidney MT and brain AChE were key biomarkers to discriminate fish of different sites. So, we suggest using these biomarkers in future biomonitoring.     

Acute effects of chlorpyryphos-ethyl and secondary treated effluents on acetylcholinesterase and butyrylcholinesterase activities in Carcinus maenas

The acute effects of commercial formulation of chlorpyrifos-ethyl (Dursban(r)) and the secondary treated industrial/urban effluent (STIUE) exposure on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities in hepatopancreas and gills of Mediterranean crab Carcinus maenas were investigated. After 2 d of exposure to chlorpyriphos-ethyl, the AChE activity was inhibited in both organs at concentrations of 3.12 and 7.82 μg/L, whereas the BuChE was inhibited only at higher concentration 7.82 μg/L of commercial preparation Dursban(r). The exposure of crabs to Dursban(r) (3.12 μg/L) showed a significant decrement of AChE activity at 24 and 48 h, whereas the BuChE was inhibited only after 24 h and no inhibition for both enzymes was observed after 72 h. Moreover, a significant repression of AChE activity was observed in both organs of C. maenas exposed to 5% of STIUE. Our experiments indicated that the measurement of AChE activity in gills and hepatopancreas of C. meanas would be useful biomarker of organophosphorous (OP) and of neurotoxic effects of STIUE in Tunisia.     

Is the reproduction of Donax trunculus affected by their sites of origin contrasted by their level of contamination?

The reproductive cycle of bivalves is regulated by several natural environmental factors but exposure to chemical pollutants can also interfere and may result in advanced or delayed spawning season. To our knowledge, the gametogenic cycle of the suspension-feeder bivalve Donax trunculus has not yet been used as biomonitoring tool in ecotoxicological surveys. The aim of this study was to examine over a year physiological reproductive endpoints (sex-ratio, gametogenic and energy reserve cycles) and biological indices (condition index, allometry) in D. trunculus originating from two sites differing by their level of contamination. Specimens were collected bimonthly from November 2008 to October 2009 from a polluted site (Radès Méliane) and a comparatively reference site (Sidi Jehmi) in the Gulf of Tunis (Tunisia). Five stages were depicted by histological examination of gonads: undifferentiated, developing, mature, spawn and spent. Differences in the gametogenic cycle according to the site of origin of bivalves were observed. The spawning period began in March and was maximum in May in bivalves from both sites, but the percentage of spawning animals was higher in the polluted site vs the reference site. The spawning period was shorter in animals from the polluted site comparatively to the reference site. Energy reserves (glycogen, lipids) were higher in March and May comparatively to the other studied periods in bivalves from both sites. Lower energy reserves levels were usually observed in animals from the polluted site compared to the reference site. Seasonal variations of the condition index were associated to the reproductive and nutritive status of bivalves. Differences in allometry were depicted between bivalves from both studied sites. If we try to link allometry, energy reserves and reproduction, it can be hypothesized that for bivalves from the reference site, energy reserves are allocated to gametogenesis and length growth. For bivalves from the polluted site, energy reserves could be devoted to tolerance to chemical stress and to reproductive processes. Therefore, D. trunculus appears as a suitable sentinel species for the assessment of the ecotoxicological risk of contaminants such as endocrine disruptors.     

Metals bioaccumulation and histopathological biomarkers in Carcinus maenas crab from Bizerta lagoon,Tunisia

Metals concentrations and histolopathological lesions of gills and digestive gland were investigated in Carcinus maenas crabs sampled from Bizerta Lagoon and Kuriat Island (Tunisia) as control site. The concentrations of trace metals varied between tissues, sites and sampling time. The highest levels of the analysed metals in gills and digestive gland were noted in Menzel Bourguiba and Cimentery sites at both sampling times (February and July). The higher metals loads were associated with severe and various tissues alterations in contaminated crabs. We particularly noted in the gills a haemocytic infiltration, distension and enlargement of the lamellae, lifting of lamellar epithelium, necrotic lesions and fusion of lamellae in the most polluted sites (Menzel Bourguiba and Cimentery). Moreover, others pathological alterations were observed in digestive gland of crabs collected from polluted sites and with a severity site dependent. We observed necrotic tubules containing tissue debris in the lumen with more intensity in crabs collected from Cimentery site in both sampling times. The thickened basal laminae and the walling off of the tubules by haemocytes around the thickened basal laminae were more abundant at Menzel Bourguiba than at others sites. The coagulation in the thickened basal laminae was observed only at Cimentery in February. Tissues histopathological lesions were sensitive to discriminate crabs of different sites and demonstrated its usefulness in this biomonitoring study. We recommend the association of histopatholocial lesions to biochemical biomarkers in future biomonitoring studies.     

Effects of increasing temperatures on biomarker responses and accumulation of hazardous substances in rope mussels (Mytilus galloprovincialis) from Bizerte lagoon

This study examined the influence of increasing temperatures in spring and summer on biochemical biomarkers in Mytilus galloprovincialis mussels sampled from Bizerte lagoon (northern Tunisia). Spatial and seasonal variations in a battery of seven biomarkers were analyzed in relation to environmental parameters (temperature, salinity, and pH), physiological status (condition and gonad indexes), stress on stress (SoS), and chemical contaminant levels (heavy metals, polycyclic aromatic hydrocarbons (PAHs), and PCBs) in digestive glands. Integrated biological response (IBR) was calculated using seven biomarkers (acetylcholinesterase (AChE), benzo[a]pyrene hydroxylase (BPH), multixenobiotic resistance (MXR), glutathione S-transferase (GST), catalase (CAT), malondialdehyde (MDA), and metallothioneins (MT). Seasonal variations in biological response were determined during a critical period between spring and summer at two sites, where chemical contamination varies by a factor of 2 for heavy metals and a factor 2.5 for PAHs. The analysis of a battery of biomarkers was combined with the measurement of physiological parameters at both sites, in order to quantify a maximum range of metabolic regulation with a temperature increase of 11 °C between May and August. According to our results, the MT, MDA, CAT, and AChE biomarkers showed the highest amplitude during the 11 °C rise, while the BPH, GST, and MXR biomarkers showed the lowest amplitude. Metabolic amplitude measured with the IBR at Menzel Abdelrahmen—the most severely contaminated station—revealed the highest metabolic stress in Bizerte lagoon in August, when temperatures were highest 29.1 °C. This high metabolic rate was quantified for each biomarker in the North African lagoon area and confirmed in August, when the highest IBR index values were obtained at the least contaminated site 2 (IBR = 9.6) and the most contaminated site 1 (IBR = 19.6). The combined effects of chemical contamination and increased salinity and temperatures in summer appear to induce a highest metabolic adaptation response and can therefore be used to determine thresholds of effectiveness and facilitate the interpretation of monitoring biomarkers. This approach, applied during substantial temperature increases at two sites with differing chemical contamination, is a first step toward determining an environmental assessment criteria (EAC) threshold in a North African lagoon.     

Monitoring pollution in Tunisian coasts using a scale of classification based on biochemical markers in worms Nereis (Hediste) diversicolor

This paper aims to assess the marine environment quality along the Tunisian coasts using a statistical approach based on biomarkers response in the polychaete worms Nereis (Hediste) diversicolor. Worms were collected from six sites: Bizerta Lagoon, Gargour, Nakta, Mahres, Skhira and from Teboulba considered as a reference site. The biomarkers selected in this work were (1) the activities of cytochrome P450-dependent NADPH cytochrome c reductase (NADPH red) as phase I enzyme, (2) glutathione S-transferase as phase II enzyme and (3) the acetylcholinesterase activity as neurotoxicity marker. Oxidative stress was evaluated using catalase activity and malondialdehyde accumulation. For each biomarker, a discriminatory factor was calculated and a response index was allocated. For each site, a multi-marker pollution index was calculated as the sum of the response index of each of the five more discriminating biomarkers. The results show differences between sites compared with the reference samples. The multi-marker approach confirms that worms from Bizerta and Mahress have been submitted to highly polluted environment. Mahress shows the highest multi-marker pollution index, indicating a highly contamination status.     

Oxidative DNA damage levels and catalase activity in the clam Ruditapes decussatus as pollution biomarkers of Tunisian marine environment

Levels of the oxidative DNA damage 7, 8-dihydro-8-oxo-2′-deoxyguanosine (8-oxodG) and catalase (CAT) activity were measured in the digestive gland and gills of clams Ruditapes decussatus, related to the presence of pollutants along Tunisian marine environment. Increased levels of CAT were observed in tissues of clams from all the sites studied, compared to control values, and elevated 8-oxodG levels were observed at specific sites. Results obtained in this work indicate that the measurement of 8-oxodG levels and CAT activity in tissues of R. decussatus is promising in pollution monitoring studies of the Tunisian marine environment.     

Polychlorinated biphenyls (PCBs) and Polybrominated Diphenyl Ethers (PBDEs) in surface sediments from Monastir Bay (Tunisia,Central Mediterranean): Occurrence,distribution and seasonal variations

An assessment of PCB and PBDE contamination of surface sediments in Monastir Bay was carried out in two contrasted seasons of the year. Samples were collected from 5 sites and analyzed for the ∑₇ marker PCBs (i.e. PCBs 28, 52, 101, 118, 138, 153 and 180) and ∑₄ PBDE congeners (PBDEs 47, 99, 119 and 153) by GC/ECD. Concentrations of both PCBs and PBDEs showed seasonal variations. PCB concentrations were in the range of 3.1–9.3 ng g⁻¹ and 1.1–8.1 ng g⁻¹ in wet and dry season respectively, and sediments were considered moderately contaminated with PCBs. All PCBs analyzed were detected in surface sediments. PCB 153 and 52 congeners showed the highest relative abundance in both winter and summer. PBDE concentrations ranged from not detect to 0.1 ng g⁻¹, with only BDE-47 congener detected in sediments and only in winter. Analysis of spatial and seasonal variations indicated that PCB distribution is governed by hydrodynamics and temporal variability of inputs. While the PCB contamination appeared to be mainly land-based, PBDEs are suspected to originate from atmospheric deposition.