No abstract

Algeria is facing an endemic drought spread over 40 years and the lack of rainfall makes us fear the worst for the country's water security. The variability in the amount of rainfall and its irregularities in time and space are the main causes of the behavior of a climatic regime.This work focuses on the analysis of climatic data provided by the google earth engine platform in order to detect temporal changes in the hydrometeorological series.The climatic results of our Mekerra watershed show a very irregular hydrometeorological system, a long dry season, an LST that reaches 54 C°, an average annual rainfall amount is 390.41 mm and a rainfall deficit estimated at 30%, a very low rainfall deficit of a maximum value of 0.42 and an NDWI globally negative.

Our work consists in characterizing the phytoplanktonic biodiversity of lake Sidi Mhamed Benali, also, biotic parameters were employed to assess lake trophic conditions, by Multivariate Analysis and by the ecological indices, during the period which extends from March to May 2021.The results of the phytoplankton analysis allowed us to list 89 species divided into 6 classes (Diatoms, Chlorophyceae, Euglenophyceae, Cyanophyceae, Cryptophyceae and Dinophyceae).The general composition of the phytoplankton of the lake is dominated by Diatoms with 34 taxa, or 36.62% of the phytoplankton community, represented mainly by the following genera: Cyclotella, Nitzschia and Fragilaria, followed respectively by Chlorophyceae with 25 taxa, or 31.81% of the total population, they are represented mainly by Oocystis, Tetraspora and Closterium, Eugenophyceae with 13 taxa, a proportion of 12. 82%, the Cryptophyceae: groups 5 taxa, with a proportion of 10.44%, the Cyanophyceae: counts 9 taxa, with a proportion of 6.88%, the Dinophyceae which groups 3 taxa, with a proportion of 1.42%. Moreover, the waters of the lake are classified as waters of average quality and are in as hypereutrophic state.

This study was accomplished with the intention of developing a new strategy of conflict against the grubs of C pipiens, vectors of parasitical diseases, by bringing a major interest in the use of essential oils of plants as bio-insecticide. The method of job which we adopted, aimed at the valuation of the larvicide activity of the plant material of R officinalis in this species of mosquito collected from the MEKKERA wadi of the city of SIDI BEL ABBES. The results obtained show that the essential oil extracted from R officinalis manifested toxicity towards fourth-stage larvae in Culex pipiens, with a concentration-response relationship. Analysis of the data shows that R. officinalis causes a reduction in several morphometric parameters such as the width of the thorax, the weight and the body volume of the larval stage 4 individuals of C pipiens compared to the controls.

The aim of our work is to evaluate the antioxidant activity of two parts (leaves and roots) of a methanolic extract of Urtica dioica L. The study of the chemical composition revealed that the leaf extract is richer in polyphenols, flavonoids and tannins than the root extract. The evaluation of the antioxidant effect showed that the inhibition reached its maximum at the highest concentration (initial DPPH concentration = 5000 μg/ml) equal to 89.25 ± 0.0022% for ascorbic acid against 67.17 ± 0.0013% (p<0.05) for the methanolic extracts of the leaves and 17.36 ± 0.0040% (p<0.001) of the roots. The methanolic extract of the leaves has a strong scavenging power of the ABTS˙+ radical with an IC50 equal to 6.59 ± 0.0060 μg/ml, equal (p> 0, 05) to that of ascorbic acid (4.67± 0.0044 μg/ml) and pyrogallol (IC50= 548.7 ± 0.084 μg/ml), with an IC50 of 481.2 ± 0.34 μg/ml for roots, against the latter. Keywords: Urtica dioica L., antioxidant activity, a, leaves, roots.