Our study attempted to monitor the quality of water in Medjarda basin (Northeastern Algeria) and to provide baseline information of heavy metals in the water as well as in a potential amphibian biosentinel, the spiny toad, Bufo spinosus. We measured pH, temperature, dissolved oxygen and biological oxygen demand of water and levels of heavy metals in toad skin using an atomic absorption flame spectrophotometer. Lead (Pb) concentration in water and in toad skin at all sites exceeded respectively 60 and 96 times the standard reference values. The heavy metal concentrations, in descending order, in water and in male toad skin were as follows: Pb > Fe > Cu > Zn and Fe > Pb > Zn > Cu respectively. This study highlights the ecological status of the surrounding areas upstream of the Medjarda basin as being a point source of heavy metal pollution. It is further stated that a non-invasive skin removal is an ethically sound technique to evaluate heavy metal accumulation in aquatic animals like toad, without euthanizing the specimens and making any loss to biodiversity of the species.

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Annaba is famous as an agricultural region. The main crops are water melon and tomatoes. These crops grow in the summer, thus need intensive irrigation that requires an overexploitation of water, which leads to an imbalance of freshwater-saltwater interface. To explain the marine intrusion and its extension, we examined the information given by geomorphologic, hydrochemistric and hydrodynamic studies. The studied area is characterized by horst and graben structures. The effects well localized of those faults allow to explain the presence of preferential areas of flow. The calculated ratio values were compared to critical level values (Mg/Ca = 4.5, SO 4 /Cl = 0.1 and Cl -/conductivity < 0.30). The obtained results show that the ratio values are over the limits, presenting a possible marine intrusion. This intrusion could particularly be from the Salines, regions in the North to Besbes in the South, which explains the water's salinity in this region, despite its distance from the sea.

Résumé :La nappe côtière de Guerbes est contenue dans les sables dunaires, ces formations très perméables facilitent les échanges entre la nappe et son environnement. Les nombreux marécages présents peuvent influencer le chimisme des eaux. Les eaux des puits présentent une certaine minéralisation, caractérisée par des valeurs importantes de la conductivité électrique de l'ordre de 4000 µS cm -1 .La zone d'étude est caractérisée par une pluviosité importante de l'ordre de 1000 mm an -1 , cet apport en eau douce n'atténue pas beaucoup la salinité des eaux dont la valeur reste considérablement influencée par la mer. Les échanges directs ou indirects s'effectuant entre la nappe et la mer semblent influencer cette salinité. Par le biais de ce travail, nous allons essayer de mettre en évidence cette relation de cause à effet entre la salinité des eaux de la nappe et la mer.