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Bosch-Belmar M.,University of Salento | Bosch-Belmar M.,Consorzio Nazionale Interuniversitario per le Science Del Mare | M'Rabet C.,National Agronomic Institute of Tunis | Dhaouadi R.,Ecole Nationale de Medecine Veterinaire | And 6 more authors.

Jellyfish are of particular concern for marine finfish aquaculture. In recent years repeated mass mortality episodes of farmed fish were caused by blooms of gelatinous cnidarian stingers, as a consequence of a wide range of hemolytic, cytotoxic, and neurotoxic properties of associated cnidocytes venoms. The mauve stinger jellyfish Pelagia noctiluca (Scyphozoa) has been identified as direct causative agent for several documented fish mortality events both in Northern Europe and the Mediterranean Sea aquaculture farms. We investigated the effects of P. noctiluca envenomations on the gilthead sea bream Sparus aurata by in vivo laboratory assays. Fish were incubated for 8 hours with jellyfish at 3 different densities in 300 l experimental tanks. Gill disorders were assessed by histological analyses and histopathological scoring of samples collected at time intervals from 3 hours to 4 weeks after initial exposure. Fish gills showed different extent and severity of gill lesions according to jellyfish density and incubation time, and long after the removal of jellyfish from tanks. Jellyfish envenomation elicits local and systemic inflammation reactions, histopathology and gill cell toxicity, with severe impacts on fish health. Altogether, these results shows P. noctiluca swarms may represent a high risk for Mediterranean finfish aquaculture farms, generating significant gill damage after only a few hours of contact with farmed S. aurata. Due to the growth of the aquaculture sector and the increased frequency of jellyfish blooms in the coastal waters, negative interactions between stinging jellyfish and farmed fish are likely to increase with the potential for significant economic losses. © 2016 Bosch-Belmar et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Gsim K.,National Agronomic Institute of Tunis | Romdhane M.S.,National Agronomic Institute of Tunis | Jupsin H.,University of Liege | Vasel J.L.,University of Liege | Marouani L.,National Sanitation Utility ONAS
Desalination and Water Treatment

Korba’s wastewater treatment plant is a conventional activated sludge, followed by three maturation ponds in series. During this study, pH, temperature, dissolved oxygen (DO), chemical oxygen demand, biochemical oxygen demand, suspended solid, and feacal bacteria were monitored.The interactions between the physicochemical and biological parameters involved in the natural disinfection process are presented and discussed. In situ analyses were also conducted to study the seasonal variation of phytoplankton, zooplankton, and daily fluctuations of physicochemical parameters. This work shows the efficiency of the maturation ponds to improve the quality of treated water from existing activated sludge treatment plants. Light has a main role in the removal of feacal coliform in maturation ponds. It has a synergistic effect with pH, DO and temperature in the ponds. Regarding the influence of the operating conditions on the decay of Escherichia coli and streptococci in the ponds, a predominance of high pH, DO, and temperature was observed. The results show a direct relationship between DO increase and pH. Improving abiotic conditions in the spring (rise in temperature, photoperiod, and light intensity) and the presence of nutrients in summer promote more algal diversity and density of Cyanobacteria (Oscillatoria), chlorophyceae (Chlamydomonas sp.), Euglenophyceae (phacus), and Diatoms (Cyclotella). © 2014, © 2014 Balaban Desalination Publications. All rights reserved. Source

Guettaya I.,National Agronomic Institute of Tunis | El Ouni M.R.,National Agronomic Institute of Tunis
Frontiers of Structural and Civil Engineering

The present paper examines the evaluation of liquefaction potential of an earth dam foundation in Tunisia. The assessment of soil liquefaction was made using deterministic and probabilistic simplified procedures developed from several case histories. The data collected from the field investigation performed before and after the vibrocompaction are analyzed and the results are reported. The obtained results show that after vibrocompaction, a significant improvement of the soil resistance reduces the liquefaction potential of the sandy foundation. Indeed, in the untreated layers, the factor of safety FS drops below 1 which means that the soil is susceptible for liquefaction. However, in the compacted horizons, the values of FS exceed the unit which justifies the absence of liquefaction hazard of the foundation. © 2014, Higher Education Press and Springer-Verlag Berlin Heidelberg. Source

Ben Ammar I.,University of Lorraine | Ben Ammar I.,National Agronomic Institute of Tunis | Teletchea F.,University of Lorraine | Milla S.,University of Lorraine | And 4 more authors.
Fish Physiology and Biochemistry

The effect of a constant photoperiod on the inhibition of male and female reproductive cycles was studied in pikeperch Sander lucioperca. Over a 153-day period, batches of pikeperch (2 years, 950 g) breeders were kept under either under natural or artificial photoperiod conditions (24L:0D) (30–35 fish/tank, triplicate) and sampled in late June (start of the photoperiod decrease in natural conditions), late August (start of temperature decrease) and late November (exogenous vitellogenesis) (7–10 fish/tank/sampling date). Morphological parameters, sexual steroids, alkaline-labile phosphate (µg/mL) levels and gamete developmental stages were investigated. Gonado-somatic index (%), developmental stages and sexual steroid levels (17β-estradiol, testosterone and 11-ketotestosterone, ng/mL) in both sexes and oocyte diameter (µm) and plasma alkaline-labile phosphate (µg/mL) in females were lower in response to a continuous lighting (24L:0D). In both sexes, continuous lighting applied in June for 153 days totally inhibited or delayed the onset of the reproductive cycle. In conclusion, photoperiod manipulation can be used to delay the pikeperch reproductive cycle, even if temperature decreases. This is the first report of the inhibitory effect of photoperiod on the onset of the reproductive cycle in pikeperch. © 2014, Springer Science+Business Media Dordrecht. Source

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