Effectiveness of strategies at reducing sand temperature to mitigate potential impacts from changes in environmental temperature on sea turtle reproductive output

Sea turtle reproduction is heavily influenced by environmental temperature. Thus, projected changes in global temperatures are predicted to alter their reproductive output (e.g. hatchling sex ratio and success). Management strategies to mitigate potential threats have been identified, but little is known about their effectiveness. We tested how effective sprinkling nests with water and shading is at reducing sand temperature. We compared sand temperature at average green turtle (Chelonia mydas) nest depth in a controlled environment with 5 different treatments: (1) shade (S), (2) shade with sprinkling during the day (SD) and (3) at night (SN), and (4) sprinkling during the day (ED) and (5) at night (EN) both exposed to sunlight. Not all strategies reduced the sand temperature; treatments with sprinkling during the day and shading on rainy days had warmer temperatures (0.83 ± 1.20 °C and 0.96 ± 0.41 °C respectively) than control treatments. Sprinkling during the night at an exposed and shaded setting were most effective at reducing sand temperature (with sand temperature on average 2.23 ± 0.66 °C and 1.43 ± 0.94 °C lower than control, respectively). These strategies could potentially be effective in counteracting increases in temperature at nesting grounds used by the northern Great Barrier Reef green turtle by 2030, where predictions are for an increase of 0.2–1.8 ± 0.01–0.37 °C. The effectiveness of strategies will likely vary regionally depending on the beach environment and setting used for the strategy.