Potential impacts of sea level rise and beach flooding on reproduction of sea turtles

Climate change scenarios predict an increase in global temperature and sea level rise. For sea turtles, the association between sea level rise, nest water content and temperature along the beach may influence embryo development and offspring survival. Over three consecutive years (2016 – 2018), a field experiment was conducted on Boa Vista island, Cabo Verde, to assess the potential impacts of tidal inundation on hatching success and hatchling phenotype in loggerhead sea turtles (Caretta caretta). Ninety-three groups of three nests each (N = 279) were relocated to a 5 km stretch of the same beach. Nests in each group were placed at regular intervals of 30 to 60 m across three zones of the beach: the lower “wet” zone, where tidal inundation was a risk, a middle zone, and the upper vegetated zone. Mean emergence and hatching success in the wet treatment was 12.0% and 18.9% respectively. In the middle zone it was 25.6% and 39.5%. In the vegetated zone it was 47.2% and 57.1%. Male hatchling production was severely reduced in the wet zone, probably by nest inundation, with the few hatchlings produced being predominantly male. Female body size and clutch size both had a significant impact on hatchling production and hatchling phenotype. In response to increased global temperatures, male hatchling production may continue in nests laid in areas of high flooding risk. The relocation of clutches to the upper beach areas as a conservation plan could be implemented to reduce the mortality of nests by high tide.