Meeting Abstract
72.5 Sunday, Jan. 6 Tidal ventilation and sea turtle O’CONNOR, M. P.*; HONARVAR, S.; SPOTILA, J. R.; Drexel Univ.; Drexel Univ.; Drexel Univ. mike.oconnor@drexel.edu
Developing sea turtle embryos experience relative hypoxia and hypercarbia because the sand around their deep nests impedes gas transport. Thus oxygen absorbed and carbon dioxide released by the embryos leads to local decreases in O2 concentration and increases in CO2 concentration. This hypoxia/hypercarbia has been implicated in embryonic mortality. In addition to intra-nest factors that affect gas transport, we have recently shown that nest density (nests per unit area) can affect gas concentrations. To assess under what beach conditions and nest densities gas concentration can become limiting, we sought to predict gas concentrations for different nest densities. Tidally induced gas flows are potentially important in ventilating nests, but the magnitude of the ventilatory effects remains controversial, uncertain, and difficult to measure or estimate. Thus, we explicitly modeled gas and heat exchanges for developing turtle embryos via both classically considered diffusive pathways and via tidally induced convection. To estimate convective exchanges, we numerically solved the Stokes equations for creeping flow through porous materials using sand properties and tidal water table changes culled from the literature. Simulation results suggest that 1) tidal water table changes like those measured on sea turtle nesting beaches can significantly affect gas concentrations (O2, CO2 , N2) at the nest, 2) tidal ventilation has a smaller effect on nest temperatures because of the volumetric heat capacity of air is much smaller than that of sand, and 3) nest density (distance between nests) can significantly affect nest gas concentrations. Previously considered intra-nest factors (nest depth, clutch mass, metabolic rate) also appear important. Our results also suggest that low RQ ratios could create problems for diffusion only models of nest gas exchange because they can lead to changes in the total pressure at the nest.
