Assessment of sediment physiochemical properties, microbial and predicted functional diversity in mangrove eco-restoration sites of Hamata, Mangrove Bay, and Saffaga along the Egyptian Red Sea coast

Microbial communities perform important roles in nutrient cycling, degradation of environmental pollutants, and support of various life forms on Earth. Mangroves live in very harsh environments, and if not for the existence of several microbial species in their ecosystems, they would not survive. The Egyptian Red Sea coast is dominated by two mangrove species, Avicennia marina and Rhizophora mucronata, which serve as breeding grounds for marine organisms and aid in carbon sequestration. Despite their ecological significance, comparative studies examining the physiochemical properties and heavy metal concentration of mangrove sediments of two dominant species along the Egyptian Red Sea coast (Hamata, Mangrove Bay, and Saffaga) and their relationship to microbial and functional diversity are scarce. Our findings revealed significant differences in sodium ions, potassium ions, organic carbon, and bulk density at 30-50 cm depth across the locations. Heavy metal analysis revealed significantly lower concentrations of zinc and manganese and high concentrations of copper in sediment samples collected from Mangrove Bay at all sampling depths. Metagenomics analysis revealed that the dominant phyla across the three sites were Pseudomonadota, Bacillota, and Bacteroidota, along with Actenomycetota, and Chloroflexota, and unclassified bacteria. Within the phylum Bacillota, several major classes were identified, including Bacillota_A_368345, Bacillota_I, and Bacillota_C. Functional prediction revealed a higher abundance of microbes involved in energy metabolism and carbon cycle, whereas a lower abundance of microbes involved in sulfur and nitrogen cycles was noted across the sites. In conclusion, the identification of different microbial communities in sediments collected along the Egyptian Red Sea coastal areas suggests the role of different mangrove species and human activities in recruiting unique microbial species involved in promoting their survival under different environmental factors.