Meeting Abstract

52.1  Thursday, Jan. 6  Tidal ventilation of sea turtle nests HONARVAR, Shaya; O’CONNOR, Michael*; Drexel Univ.; Drexel Univ. mike.oconnor@drexel.edu

Sea turtles bury their nests as much as 70-80 cm deep and the sand above the nest represents an important resistance to respiratory gas exchange. Tidal movements of the water table under the nest can ventilate the nest, reducing hypoxia/hypercapnia. We have previously modeled nest gas exchanges, using previously measured tidal water table movements, and found the effects on nest gas concentrations to be of limited importance. We recently measured tidal water table fluctuations on nesting beaches in Bioko, Equatorial Guinea. Unexpectedly large water table movements suggest that tides can ventilate nests more vigorously than previously estimated. The amplitude and timing of water table fluctuations varied with distance of the nest from the water, with lunar phase, and between successive tides. Amplitude of the tidal water table fluctuations was attenuated with increased distance from the water. Simulations using our measured tidal fluctuations, show the potential to decrease time averaged oxygen deficits and carbon dioxide concentrations by 25-30%. Peak predicted oxygen deficits were also ameliorated, in contrast to predictions with smaller water table fluctuations. Thus, water table movements and potential effects on respiratory gas exchange, metabolism, and developmental rates all increase in nests laid closer to the water. Effects on nest metabolism and development are unclear because tidal ventilation also induces cycles of nest gas concentrations, whose effects on eggs are unexplored. Trough water table levels lagged 2-3 hr behind low tides. Simulations suggest that peak and trough gas concentrations can also be temporally offset from extremes of water table movements. Thus, measuring nest pressures or gas concentrations at the times of low and high tide may obscure the effects of tidal ventilation of sea turtle nests.