Effect of salinity on valves morphology in freshwater diatoms

Increased salt concentration is one of the most widespread problems affecting freshwater worldwide. Aquatic communities, and in particular periphytic diatoms, react to this alteration in water quality by modifying their structural parameters and physiology at the individual level, which is commonly manifested by the appearance of teratological forms. The present work presents the results of an experimental laboratory study in which a biofilm grown on artificial substrates was subjected to a gradient of water conductivities for 4 weeks. The results show an increase in the number of deformed valves over time proportionally to the increase in conductivity for each experimental treatment. These effects are also verified by analyzing the concentration of chlorophyll-a in the experimental biofilms, which demonstrate a metabolic response to the induced osmotic stress. No changes were recorded; however, in species richness or diversity of taxa present in the treatments. Our results, therefore, confirm at the experimental level numerous previous field observations about the harmful effect of salinity on periphytic diatoms, and also their ability to reintegrate with the new stress conditions.

First evidence of plastic pollution in beach sediments of the Skikda coast (northeast of Algeria)

This study is the first attempt to provide original data on plastics debris occurrence in beach sediments of the Gulf of Skikda in Algeria (southwestern Mediterranean). Sediment samples from seven beaches were collected to extract, quantify and characterize mesoplastics and microplastics. Particles were classified by size into mesoplastics (5-25 mm) and large microplastics (1-5 mm). Overall, microplastics were the most abundant size fraction in terms of number of items. The average mass of mesoplastics was twice that of microplastics, revealing a notable reservoir of plastics that is scarcely ever reported in the literature. The predominant types were fragments and pellets, white/transparent in color. The average concentrations of total plastic were 1067.19 ± 625.62 items/m², 106.98 ± 62.39 items/kg, and 50.65 ± 9.82 g/m², showing variability between beaches and within sampling sites. Thus, the Skikda coast has high levels of pollution compared to other areas of the Mediterranean Sea.

Abundance and spatial distribution of the structure supporting the nest of White Stork Ciconia ciconia in Guerbes-Sanhadja wetland eco-complex, northeastern of Algeria

In the present investigation, the spatial distribution of the nest of White Stork Ciconia ciconia was examined. Spearman's rank-order correlations test and the principal component analysis (PCA) were applied to a total of 227 nests recorded in the Guerbes-Sanhadja wetland eco-complex, northeastern of Algeria, over seven sites, for which the percentage of occupied nests reaches 89% (202 nest were occupied). Our goals are twofold: to explore the variation and distribution of the structure supporting the nest and to explain their spatial variability. The Spearman's rank-order correlation test show that steel electricity poles had non-significant correlations with tree, and only concrete electricity poles structure had statistically significant positive correlation with mobile phone antennas structure (R = 0.757; at p < .05), and the roofs of houses had statistically significant positive correlation with mobile phone antennas structure (R = 0.825; at p < .05). According to the PCA results, it was observed that the PC1, which explains 50.86% of the total inertia, further represents and synthesizes the dominant structure supporting the nest, i.e., tree, steel electricity poles, and concrete electricity poles, which were strongly correlated with PC1, having a component loading nearly equal to 0.766, 0.821, and - 0.929, respectively, while the PC2, which explains 30.30% of the total inertia, includes the structure rarely recorded in the studied region, i.e., wooden electricity poles and the roofs of houses.