Potential impacts of environmental bacteria on the microbiota of loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtle eggs and their hatching success

• Published in: MicrobiologyOpen (Weinheim) 2023-06, Vol.12 (3), p.e1363-n/a
• Main Authors: McMaken, Colleen M., Burkholder, Derek A., Milligan, Rosanna J., Lopez, Jose V.
• Format: Article
• Language: English
• Subjects: Animals; Bacteria - genetics; beach sand; eggs; hatching success; Microbiota - genetics; Nesting Behavior; Original; Pseudomonas; Sand; sea turtle; Turtles
• ISSN: 2045-8827; 2045-8827
• DOI: 10.1002/mbo3.1363

Sea turtle hatching success can be affected by many variables, including pathogenic microbes, but it is unclear which microbes are most impactful and how they are transmitted into the eggs. This study characterized and compared the bacterial communities from the (i) cloaca of nesting sea turtles (ii) sand within and surrounding the nests; and (iii) hatched and unhatched eggshells from loggerhead (Caretta caretta) and green (Chelonia mydas) turtles. High throughput sequencing of bacterial 16S ribosomal RNA gene V4 region amplicons was performed on samples collected from 27 total nests in Fort Lauderdale and Hillsboro beaches in southeast Florida, United States. Significant differences were identified between hatched and unhatched egg microbiota with the differences caused predominately by Pseudomonas spp., found in higher abundances in unhatched eggs (19.29% relative abundance) than hatched eggs (1.10% relative abundance). Microbiota similarities indicate that the nest sand environment, particularly nest distance from dunes, played a larger role than the nesting mother's cloaca in influencing hatched and unhatched egg microbiota. Pathogenic bacteria potentially derive from mixed‐mode transmission or additional sources not included in this study as suggested by the high proportion (24%–48%) of unhatched egg microbiota derived from unknown sources. Nonetheless, the results suggest Pseudomonas as a candidate pathogen or opportunistic colonizer associated with sea turtle egg‐hatching failure. Here we used 16S rRNA gene sequencing to characterize and compare the bacterial communities of hatched and unhatched eggshells from loggerhead and green sea turtles to those in the cloaca of nesting sea turtles and sand within and surrounding the nests. Significant differences were identified between hatched and unhatched egg microbiota with the differences associated predominately with Pseudomonas spp., found in higher abundances in unhatched eggs than hatched eggs. Microbiota similarities indicate that the nest sand environment played a larger role than the nesting mother's cloaca in influencing egg microbiota. However, additional unknown sources may contribute to pathogenic bacteria introduction into unhatched eggs.