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

## TL;DR

This study reviews gut bacteria in wild and captive green sea turtles, finding differences that could impact their health and conservation.

## Contribution

The study systematically characterizes microbial shifts between wild and captive green sea turtles, linking them to environmental factors.

## Key findings

- Bacillota is the most abundant phylum in captive turtles but ranks second in wild turtles.
- Pseudomonadota is more prevalent in wild turtles compared to captive ones.
- Microbial shifts may be influenced by environmental differences between wild and captive settings.

## Abstract

Gut bacteria are a critical determinant of health, but they are not fully defined in green sea turtles (Chelonia mydas). This review determined what constituted dominant gut bacterial phyla in green sea turtles; probable microbial shifts between wild and captive populations were identified. These potential microbial shifts that are likely to be shaped by environmental factors are important in guiding management, rehabilitation, and conservation of green sea turtles.

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.