Characterisation of the Gastrointestinal Microbiome of Green Sea Turtles (Chelonia mydas): A Systematic Review

The gut microbiome of sea turtles is essential for their ecological resilience and adaptation to environmental stressors. We hypothesised that different gut microbial profiles existed between green sea turtles kept in captivity and those in the wild. The aim of this systematic review was to determine dominant bacterial phyla in the gut microbiomes of wild and captive green sea turtles. Comparison of the top four bacterial phyla revealed that Bacillota was the most abundant phylum in captive turtles (40.9–87.5%), but it only ranked second (3.5–57.8%) in wild turtles. Bacteroidota had comparable relative abundance in captive (8.7–45.6%) and wild (3.6–43.1%) populations. By contrast, the relative abundance of Pseudomonadota was higher in wild turtles (6.2–68.1%) compared to the captive population (0.1–6.6%). Verrucomicrobiota was less prevalent in wild and captive populations, with relative abundances ranging from 0.28 to 5.4% and 2.3 to 7.2%, respectively. These findings highlight a putative gut microbial shift between wild and captive green sea turtle populations. This shift may be shaped by variations in environmental factors in captivity or the wild. Nonetheless, the significance of these putative changes is still unknown; the potential to use microbial shifts to guide management, rehabilitation, and conservation of green sea turtles is promising, but remains limited.