National Institute of Marine science and Technologies

of Marine, Tunisia

National Institute of Marine science and Technologies

of Marine, Tunisia
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Abdennadher M.,National Institute of Marine science and Technologies | Zouari A.B.,National Institute of Marine science and Technologies | Sahnoun W.F.,National Institute of Marine science and Technologies | Alverca E.,Portuguese Environment Agency | And 2 more authors.
Harmful Algae | Year: 2017

In the last few decades, the frequency of the toxic benthic dinoflagellate Ostreopsis cf. ovata proliferation has increased in the Mediterranean Sea. These blooms are associated with harmful effects on human health and the environment. The present work provides the first long term study on the spatio-temporal distribution of O. cf. ovata in relation to physical parameters in the Gulf of Gabès coastal waters (south-eastern Mediterranean Sea), as well as its morphological, molecular and physiological features. The strains of O. cf. ovata were identified morphologically by light and epifluorescence microscopy. The morphology and the size range of cultured strains were similar to those described regarding O. cf. ovata isolated from the Mediterranean Sea. The ultrastructural analysis of O. cf. ovata cells using the transmission electron microscopy showed the presence of numerous vesicles (VE) containing spirally coiled fibers (SCFs) connected to the mucus canal (CH). The phylogenetic tree based on the internal transcribed spacer region containing the 5.8S rDNA (ITS-5.8S rDNA) revealed that O. cf. ovata strains were placed into the Mediterranean/Atlantic clade. In addition, O. cf. ovata toxicity was evaluated by the mouse bioassay and a dose level ≥ 4 × 104 cells was found to be lethal to mice. The examination of the O. cf. ovata occurrence in the Gulf of Gabès at a large temporal scale (1997–2012) revealed a clear seasonal pattern with dominance from midsummer (July) to late autumn (November). Furthermore, a positive correlation was found between the abundance of O. cf. ovata and salinity, whereas no correlation was found as regards temperature. The occurrence of O. cf. ovata was only detected at salinity above 35 and the highest concentrations were observed at 45. Laboratory experiments confirmed such a result and showed that isolated O. cf. ovata strains had optimal growth at salinity ranging between 35 and 45, with its peak at 40. © 2017 Elsevier B.V.

SaiDi S.A.,University of Sfax | Azaza M.S.,National Institute of Marine science and Technologies | Abdelmouleh A.,National Institute of Marine science and Technologies | Pelt J.V.,University Hospitals Leuven | And 2 more authors.
Aquaculture Research | Year: 2010

A 45-day feeding trial was conducted to study the effect of replacing dietary fish meal (FM) with a tuna by-product meal (TBM) on the growth, feed efficiency, carcass composition and stress oxidative status of juvenile Nile tilapia, Oreochromis niloticus L.). Triplicate groups of fish (2.21 ± 0.01 g) were fed on four iso-nitrogenous and iso-energetic diets. The control diet (A0) used FM as the sole source of animal protein. In the other three diets (A10-A30), 33%-100% of FM was substituted by TBM at 10% increments. There were no significant differences (P>0.05) in growth performance among fish fed on diets A0, A10 and A20. Fish fed these experimental diets (i.e., A0, A10 and A20) showed significantly (P<0.05) better daily mass gain, specific growth rate and protein efficiency ratio than those fed on diet A30. Feed conversion ratio increased with increasing TBM content, but only the value found in fish fed on diet A30 differed significantly (P<0.05) from the other treatments. The fish accumulated increasing quantities of lipids and decreasing levels of ash in their carcasses with increasing levels of dietary TBM. At the end of the experimental period, a significant increase (P<0.001) in catalase and glutathione S-transferase activities was seen only in groups fed on diet A30. Similarly, a significant enhancement in glutathione peroxidase and superoxide dismutase activities was observed in groups fed on diets A20 and A30 compared with the other groups. The results show that this product can be included up to 20% in practical Nile tilapia diets without any detrimental effects. © 2010 The Authors. Aquaculture Research © 2010 Blackwell Publishing Ltd.

Saidi S.A.,University of Sfax | Saidi S.A.,University Hospital Gasthuisberg | Azaza M.S.,National Institute of Marine science and Technologies | Windmolders P.,University Hospital Gasthuisberg | And 2 more authors.
Experimental and Toxicologic Pathology | Year: 2013

Heavy metals can accumulate in organisms via various pathways, including respiration, adsorption and ingestion. They are known to generate free radicals and induce oxidative and/or nitrosative stress with depletion of anti-oxidants. Tuna by-product meal (TBM) is rich in proteins and can, therefore, offer an attractive protein source for animals. This study was undertaken to assess the effects of metals present in TBM, namely cadmium (Cd), lead (Pb), and mercury (Hg), separately or in combination with oxidative stress, on cell viability. Three cell models: rat liver FTO2B, human hepatoma HepG2, and human hepatic WRL-68, were used. Cell viability was determined following exposure to various concentrations of the metals. Two antioxidant genes, catalase (CAT) and superoxide dismutase (SOD), were measured to obtain a better understanding of oxidative stress-associated gene expression. Among the metals present in TBM, only Cd at a concentration of 30μM was noted to exhibit cytotoxic effects. This cytotoxicity was even more pronounced after co-stimulation with H2O2, used to mimic systemic oxidative stress. At non-toxic concentrations, Hg and Pb were noted to aggravate oxidative stress toxicity. The results further revealed that exposure to Cd, Pb, and a co-stimulation of H2O2 with Hg resulted in the increased expression of antioxidant gene SOD. A risk assessment of toxic contaminants in TBM indicated that food safety objectives should consider the human health impacts of foods derived from animals fed on contaminated meal and that much care should be taken when TBM is used in animal diet. © 2013 Elsevier GmbH.

Azaza M.S.,National Institute of Marine science and Technologies | Khiari N.,National Institute of Marine science and Technologies | Dhraief M.N.,National Institute of Marine science and Technologies | Aloui N.,National Institute of Marine science and Technologies | And 2 more authors.
Aquaculture Research | Year: 2015

The effect of various dietary starch to proteins ratios (STA/P) on growth performance, oxidative status and liver enzyme activities involved in intermediary metabolism in juvenile Nile tilapia was evaluated. Four isocaloric-practical diets (12.73 MJ kg-1 digestible energy) with increasing STA/CP ratios were formulated. These were designated D0 (344 g crude protein (CP) and 163.5 g starch (STA) kg-1), D1 (310 g CP and 243 g STA kg-1), D2 (258 g CP and 322 g STA kg-1) and D3 (214 g CP and 401 g STA kg-1). Each diet was fed to triplicate groups of 60 fish (2.7 g) for 45 days. Compared with the control diet (D0), significantly (P < 0.05) depressed growth and feed efficiency were observed only in the groups fed on diet D3. The activities of hepatic enzymes involved in glycolysis and lipogenesis pathways were significantly enhanced in groups fed on diet D3 compared with other diets. A significant (P < 0.05) increase in catalase activity was detected only in groups fed on diet D3. Similarly, a significant (P < 0.05) enhancement in superoxyde dismutase, glutathione S-transferases and glutathione peroxidise was observed in groups fed on diets D2 and D3 compared with other diets. Results demonstrate the ability of juvenile Nile tilapia to spare protein by dietary carbohydrate. © 2013 John Wiley & Sons Ltd.

Boulares M.,Higher Institute of Food Industries of Tunis ESIAT 58 Alain Savary Street | Mankai M.,Higher Institute of Food Industries of Tunis ESIAT 58 Alain Savary Street | Sadok S.,National Institute of Marine science and Technologies | Hassouna M.,Higher Institute of Food Industries of Tunis ESIAT 58 Alain Savary Street
Journal of Food Safety | Year: 2017

The inhibition capacity of four combinations of three lactic acid bacteria (LAB) (Lactococcus lactis, Lactobacillus plantarum and Carnobacterium piscicola) has been demonstrated against Listeria monocytogenes in fresh farmed sea bass fillets artificially contaminated. The four combinations gave promising results, having a significant bacteriostatic effect against all tested microflora, during 21 days of vacuum storage at 4 °C. Throughout storage, biochemical alteration appeared more pronounced in farmed sea bass fillets inoculated with pure Listeria, with significantly higher levels of total volatile bases (TVB-N) and trimethylamine (TMA-N). Moreover, the inoculation of LAB combinations was efficient in preventing the decrease of lipid and protein contents and preserving a good content of ω-3 fatty acids, particularly the eicosapentaenoic acid (C20:5N3) and docosahexaenoic acid (C22:6N3). Besides, the proteolytic activity on sarcoplasmic proteins (SP) and myofibrillar proteins (MP) was determined by Sodium dodecyl sulphate–poly-acrylamide gel electrophoresis, comparing the protein profile of control fish fillets with those inoculated with LAB strains or/and L. monocytogenes, during vacuum refrigerated storage. Practical Applications: Due to the increase of interest in food-grade preservatives of biological origin, food preservation became a challenge since several foodborne pathogens pose a health risk to consumers and cause serious hazard in food products. Listeria monocytogenes is an important food poisoning pathogen that can survive in lightly preserved seafood products stored at low temperatures. Considering this, biopreservation of fresh farmed sea bass (Dicentrarchus labrax) fillets during 21 days of vacuum storage at 4 °C using four combinations of LAB strains originating from fresh seafood and having important antagonistic effect, and low proteolytic and lipolytic activities, is a promising way to inhibit the growth of pathogenic bacteria such as L. monocytogenes without changing the quality of the product and to guarantee adequate product safety. © 2016 Wiley Periodicals, Inc.

Gualdi S.,Italian National Institute of Geophysics and Volcanology | Somot S.,Meteo - France | Li L.,French National Center for Scientific Research | Artale V.,ENEA | And 20 more authors.
Bulletin of the American Meteorological Society | Year: 2013

A number of scientific initiatives and projects were undertaken to assess the possible changes that anthropogenic global warming potentially induced in the climate of the European continent and of the Mediterranean region. Scenario simulations were specifically conducted with the aim of quantifying the possible future climate change in the European and Mediterranean region. These scenario simulations were designed and performed in the framework of European Union EU) projects, such as the Prediction of Regional Scenarios and Uncertainties for Defining European Climate Change Risks and Effects (PRUDENCE) and Ensemble-Based Predictions of Climate Changes and Their Impacts (ENSEMBLES). Coordinated studies were also performed to investigate and to assess the climate change signal in the Mediterranean region projected by regional and global models.

Azaza M.S.,National Institute of Marine science and Technologies | Dhraief M.N.,National Institute of Marine science and Technologies | Kraiem M.M.,National Institute of Marine science and Technologies | Baras E.,IRD Montpellier
Aquaculture | Year: 2010

This study aimed at determining the food particle sizes (diameter) that produce the fastest growth (Sopt) in juvenile Nile tilapia, and modeling the growth penalties for particles departing from Sopt. Three 14-day experiments were run with 3, 7 and 11g juveniles, which were raised in 120-L flow-through cylindro-conical tanks at 29±1°C, fed at the optimum feeding level (Ropt) and weighed at weekly intervals. In each experiment, four different sizes of pellets (diameter) were evaluated (0.5-mm intervals, 1.0-3.5mm; three replications per pellet size). At the end of each experiment, food intake and gastric evacuation rate were determined by radiographic methods following the use of ballotini labelled feed.The results indicate that i) in all experiments, specific growth rates (SGRs) are significantly depressed for the largest particles; ii) Sopt increases with increasing fish size (1.4mm at 3g, to 2.5mm at 20g); iii) the optimum particle size relative to mouth width (MW) varies only slightly with fish size (28 to 25% MW from 3 to 20g); iv) growth heterogeneity is proportional to food particle size; and, v) food intake and gastric evacuation rates are inversely proportional to food particle size. A growth model (SGR) was constructed with a stepwise multiple-regression analysis against fish size, feeding level and food particle size (R2=0.853, df=71). For a particular fish size, the growth-to-particle size relationship is a log-log second order polynomial, which implies that the growth penalty is more severe when fish are fed small than large particles. By contrast, application of food particles slightly smaller than Sopt tends to minimize growth heterogeneity. As fish size increases, the width of the SGR-to-S relationship broadens; so, the penalty for distributing particles departing from Sopt is lower, and feeding strategies are facilitated. © 2010 Elsevier B.V.

Stoch F.,Health Science University | Korn M.,DNA Laboratory | Turki S.,National Institute of Marine science and Technologies | Naselli-Flores L.,University of Palermo | Marrone F.,University of Palermo
Hydrobiologia | Year: 2016

The influence of spatial and environmental factors in explaining the structure of large branchiopod assemblages at different spatial scales is still poorly explored. We hypothesized that the extent of actual spatial connectivity, and thus the spatial distribution of a metacommunity, may depend on the environmental conditions as represented by climatic gradients and the structural characteristics of the landscape. To test this hypothesis, the distributional patterns of 14 large branchiopod species in a set of 177 temporary water bodies repeatedly sampled across Tunisia and on its main islands were analysed. Physical, chemical, morphological and climatic characteristics of the studied water bodies were collected as well, and spatial structures were described using distance-based Moran’s Eigenvector Maps. Distance-based Redundancy Analysis and variance partitioning explained more than one-half of total variation. Mantel’s autocorrelograms demonstrated that species composition was spatially autocorrelated at shorter distances in the Mediterranean part of the country than in the southern, more arid part. These results suggest that both dispersal limitation and species response to spatially structured environmental gradients might be involved in determining large branchiopod distribution in Tunisia and that these patterns may greatly vary on a regional basis. © 2016 Springer International Publishing Switzerland

Messaoudi S.,National Institute of Marine science and Technologies | Bejaoui B.,National Institute of Marine science and Technologies | Akrout F.,National Institute of Marine science and Technologies | Bel Hassen M.,National Institute of Marine science and Technologies | Sammari C.,National Institute of Marine science and Technologies
International Journal of Quantum Chemistry | Year: 2013

The heterogeneous uptake of N2O5 on mineral dust particles may play an important role in the removal of nitrogen oxides from the atmosphere. However, the reaction of N2O5 with the mineral particles is not well understood. The reaction of N2O5 with two Si(OH)4 monomers is explored using theoretical methods. This study represents a first step towards understanding the interaction of N 2O5 with the hydroxyl groups of silica particles. Energies are calculated using MP2 single point calculations on the B3LYP optimized geometries and including B3LYP thermodynamic corrections. Four mechanisms are considered for the formation of two HNO3 and one H6Si 2O7. The rate limiting activation barrier of the most favorable path is found to be 12.5 kcal mol-1. This reaction appears to be more favorable than the hydrolysis of N2O5 with one water molecule. These results are in agreement with experimental observations, which show that N2O5 reacts with OH groups of Saharan dust to form nitrate. © 2012 Wiley Periodicals, Inc.

Fathallah S.,National Institute of Marine science and Technologies | Medhioub M.N.,National Institute of Marine science and Technologies | Medhioub A.,National Institute of Marine science and Technologies | Kraiem M.M.,National Institute of Marine science and Technologies
Soil and Sediment Contamination | Year: 2012

This paper aims to assess the marine sediment quality along the Tunisian coast using clam Ruditapes decussatus embryos and larval bioassays tests. Elutriate samples prepared with sediment from four sites (Monastir Lagoon, Chebba, Mahres, and Zarat) were used for chemical analysis and clam bioassays tests (embryogenesis, larval growth. and metamorphosis). For embryogenesis test, five elutriates concentrations (12%, 25%, 50%, 75%, and 100%) were prepared. Metal concentrations were highest at the Mahres and Monastir Lagoon sites. Clam embryogenesis success was significantly (p < 0.05) reduced in all elutriates preparations at concentrations up to 50% except Chebba, where inhibition was evident at only the highest concentration (100%). Compared to the control (9.4 μm day-1), larval growth rate was significantly (p < 0.05) reduced only in two sites, Monastir Lagoon (6.8 μm day-1) and Zarat (5.6 μm day-1). However, larval survival was lower (42.9%) in elutriates prepared from Mahres sediment compared to other studied sites and control treatment. We did not note any significant (p > 0.05) effect of elutriate preparations on clam metamorphosis; conversely, survival in this stage was significantly affected in three sites (Monastir: 59.0 ± 6.7%; Zarat: 52.1 ± 6.3%, and Mahres: 64.1 ± 5.4%) compared to the control (83.2 ± 4.7%). This work shows that both clam embryos and larvae are sensitive to contaminants and can be used to evaluate sediment contamination and monitor pollution. © 2012 Copyright Taylor and Francis Group, LLC.

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