Meeting Abstract
75.1 Tuesday, Jan. 6 Biophysical factors affecting gas exchange in sea turtle nests O’CONNOR, M.P.*; HONARVAR, S.; SOTHERLAND, P.R.; SPOTILA, J.R.; Drexel Univ.; Drexel Univ.; Kalamazoo Coll.; Drexel Univ. mike.oconnor@drexel.edu
The sandy environment of developing sea turtle eggs creates a significant resistance to both diffusive and convective exchanges of respiratory gases. Data suggest that the resulting relative hypoxia and hypercarbia affect egg metabolism, development times, and hatching success. Unfortunately, the magnitudes of the induced resistances are not clear and quantiative dependences on nest depth and density or tidal convection are unknown. We modeled the effects of several environmental factors on concentrations and fluxes of O 2 and CO 2 by numerically solving the Stokes equations for creeping flow in a porous substrate. Models argue that: 1) Convection caused by metabolism with a low RQ will slightly increase both O 2 and CO 2 concentrations. 2) Forced convection due to tidal fluctuation in the underlying water table can provide moderate increases in mean O 2 and decreases in CO 2 levels, but that gas concentrations will vary cyclically with trough O 2 concentrations approximating those without tidal forcing. 3) Hypoxia and hypercarbia vary approximately linearly with egg metabolism. 4) Crowding of nests in arribada nesting species could limit O 2 concentrations and nesting success. 5) The deeper nests constructed by larger sea turtle species provide larger resistances to gas exchange. 6) Time constants for approach to equilibrium can be long enough to prevent thermal (and to a lesser extent, gaseous) equilibrium in developing nests with metabolic rates that increase with weekly half times. Such models are computationally intensive, but can be used to predict under which circumstances gaseous exchanges might limit metabolism and development.
