Bacterial Diversity of Green Turtle Eggs and Nest Sand on Samandağ Beach

Sea turtles are highly susceptible to alterations in the biological and chemical composition of their environment and are also characterized by bioaccumulation of pollutants, toxins, and pathogens. Their eggs possess flexible shells that facilitate the exchange of water with the surrounding environment, and the successful development of embryos is contingent upon a range of environmental factors and the microbial flora present in the sand. This study aimed to determine the bacterial diversity of green turtle (Chelonia mydas) unhatched dead eggs and nest sand on Samandağ Beach. High-throughput sequencing of the 16S rRNA gene V3-V4 region amplicons was conducted on nest sand and dead unhatched eggs from 8 nests on Samandağ Beach, eastern Mediterranean. The microbial composition of nest sand and unhatched dead egg samples differed significantly. Twenty-three bacterial species were more abundant in nest sand samples than in egg samples. The alpha diversity analysis revealed no statistically significant difference in hatching success (PERMANOVA, p > 0.05). However, while beta diversity exhibited a statistically significant difference (PERMANOVA, p < 0.05), these two groups demonstrated overlapping elliptical shapes with 95% confidence intervals. Many pathogenic bacterial species that may affect hatching success were detected in unhatched dead egg and nest sand samples. Achromobacter xylosoxidans and Hafnia alvei were identified for the first time in the nest sand and unhatched dead eggs of C. mydas in this study. The findings indicate that the presence of pathogenic bacteria, as well as their high abundance in the environment, is associated with the effects of hatching success. Further research is required to elucidate the role of these bacteria in shaping the egg microbiota and their impact on hatching success.