Grant: 22-031R
Project Title: The effects of nest temperatures on the skin microbiome of leatherback hatchlings
Project Manager: Jeanette Wyneken
Organization: Florida Atlantic University (Research and Educational Institute)
Grant Amount: $16,303.58
Completion Date: 2024-05-16
Summary: High nest productivity is critical for sea turtle population recovery. Yet, hatching success of leatherback clutches is highly variable with average clutch success often <50%. The current leatherback conservation status is due to many factors that perturb production. Here we focus on establishing baseline metrics of hatchling leatherback skin health because skin is the body's first line of defense. Warming climate likely affects skin health by changing the incubation environment and microbial ecosystem within nests. Long-term data that we collected shows that, unlike the other sea turtles nesting on the same beaches, the leatherback hatchlings, even from productive nests, appear to have a down-stream risks. This species' hatchlings are prone to developing skin infections in the nest and within a few weeks of emerging from their nests that can be life threatening. The propensity seems to be higher in clutches that incubate at warmer temperatures. Why? The answers require (i) characterizing the impact of clutch temperatures that changes from early spring (cooler) to warm summer on the hatchling skin microbiome. Microbiota are key components of survival in all living creatures, and the skin microbiota act in defense against harmful elements (e.g., pathogens, toxins). Yet, we know nothing about normal skin microbiota in leatherback turtles and have no idea how elevating temperatures shift the microbial assemblages. This study will be focused in Palm Beach County, a hotspot for leatherback nesting where we have ongoing clutch temperature monitoring. Using next generation sequencing, this study will provide essential data, allowing us to identify effects of clutch temperatures on skin microbiota. We also will partner this thermal and microbiome analysis with standard blood-based measures of health: packed cell volume (PCV); total solids (TS); white blood cells (WBC); protein electrophoresis (EPH). Across the season nest temperatures increase. We expect shifts in skin microbiota, PCV, TS, WBC, and EPH. Study results will be critical new perspectives for forthcoming nesting beach conservation as understanding how healthy beaches lead to healthy hatchling production will support Florida leatherback population recovery in a warming world.
Results: Field work occurred during the 2022 and 2023 nesting and hatching seasons. Neonate Sample Collection: Skin swabs were collected from neonates on the day of emergence and again at 3-4 weeks of age. Sampling followed the same procedure at both time points. Each neonate was rinsed with 50 mL of sterile nano-pure water four times. Then a sterile swab (rayon or polyester) was used to sample the animal's whole integument including the head, carapace, plastron and all four limbs. Swabbing was be repeated in duplicate for each neonate. As a negative control, prior to collection a sterile swab was held in the sample room for 20 seconds. Each swab was placed into sterile vial and was stored at -80C until DNA extraction. A total of 192 swabs were collected from neonatal leatherbacks. Nesting female sample collection: All nesting females were sampled from Juno Beach, Florida. Samples were collected during the 2022 and 2023 nesting seasons. In 2022 a total of 8 samples were collected from different turtles. In 2023 a total of 29 different turtles were sampled and 6 were sampled on two different occasions. Sampling began after egg deposition started, and once the nesting female was in the nesting fixed action pattern Prior to sampling, a 30 cm area on the cranial half of the carapace was rinsed with 500mL of sterile nano-pure twice. Then using sterile swabs (rayon or polyester) a 10 cm by 10 cm area in the rinsed region was swabbed twice. The rinsing and swabbing process was then repeated on the proximal region of the front flipper (left or right as available due to positioning). Samples were placed into a sterile tube and then on ice until they could be stored in a freezer at -80C.
Figure from Kuschke SG, Wyneken J, Cray C, Turla E, Kinsella M, Miller DL. Fusarium spp. an emerging fungal threat to leatherback (Dermochelys coriacea) eggs and neonates. Frontiers in Marine Science. 2023;10. Accessed August 14, 2023. frontiersin.org/articles/10.3389/fmars.2023.1170376