|Amy Maas, Brad A. Seibel and Patrick J. Walsh, |
Effects of elevated ammonia concentrations on survival, metabolic rates and glutamine synthetase activity in the antarctic pteropod mollusk Clione limacina antarctica, Polar Biology, 2012
Information on the effects of elevated ammonia on invertebrates in general, and polar Molluscs in particular is scant. In the present study, we sought to examine the effects of elevated exogenous ammonia on several key aspects of the physiology and biochemistry of the pteropod mollusc, Clione antarctica limacina and further to examine a possible link between elevated lipid/ trimethylamine oxide (TMAO) levels and ammonia tolerance. We determined that the 96-hour LC50 value for this species is 7.465 mM total ammonia (Upper 95% CL = 8.498 mM and Lower 95% CL = 6.557 mM), or 35.75 mg/ L NH3. While comparative data for molluscs are scant, this value is at the upper end of reported values for other species. When the effects of lower ammonia concentrations (0.07 mM total ammonia) on oxygen consumption and ammonia excretion rates were examined, no effects were noted. However, total ammonia levels as low as 0.1 mM (or 0.48 mg/ L NH3) were sufficient to elevate the activity of the ammonia detoxification enzyme glutamine synthetase by approximately 1.5 fold. These results are discussed relative to regulations for permissible aquatic ammonia concentrations and potential sources of ammonia exposure in polar regions.