Goforth, K. M. and R.R. Carthy. 2022. Tidally-driven gas exchange in beaches: implications for sea turtle nest success. Journal of Coastal Research. 38 (3): 523–537, https://doi.org/10.2112/JCOASTRES-D-21-00082.1
The success of individual sea turtle nests is influenced by nest location on the beach and the resulting incubation environment. Several abiotic factors affect nest incubation, and thus nest success, but tides and gas exchange are two of the most important. The effects of tides on nest success have been well documented in regard to overwash and inundation events. However, the possible effect of tidally-driven gas exchange has received little attention. The incursion and retreat of the saltwater wedge may cause substantial movement of gases through the beach during the tidal cycle. This study quantifies the differences in tidally-driven gas exchange among beach types and shoreline elevation levels. Carbon dioxide (CO2) efflux was used as a means of measuring gas movement through the beach to examine tidal effects across different beach zones and among different beach types. CO2 efflux was measured throughout the tidal cycle at three distinct beaches (accreting, eroding, and nourished) at Cape San Blas, Florida. There was a general pattern of CO2 efflux rising and falling throughout the tidal cycle on each beach and a difference in the CO2 efflux observed among beaches and beach zones. Efflux patterns at the nourished and eroding beaches were similar, but the nourished beach exhibited a decreased and dampened CO2 efflux pattern throughout the course of the tidal cycle. Analyses of the hatchling turtle emergence success data from 2011 to 2014 for the three beaches found that emergence success differed among the three beaches. The highest emergence success was on the nourished beach, which exhibited a relatively consistent efflux pattern. These results suggest that tidally-driven gas exchange may have implications on nest incubation and survival and are a consideration in beach restoration management and best practices for coastline conservation.