Thermal sensitivity of gill Na+/K+ ATPase activity in juvenile red drum

Abstract

The red drum is a valuable coastal species distributed throughout the southeastern US where winter cold stress can vary geographically and impact survivorship. We studied the thermal sensitivity of red drum gill Na+/K+ ATPase in order to gain insight regarding temperature effects on osmoregulatory capabilities with potential implications for overwinter survival. We collected gill tissue from age-0 juvenile red drum acclimated to a temperature of 15 °C and measured Na+/K+ ATPase activity at 1, 5, 10, 15, and 25 °C to assess function over a broad thermal range. The Arrhenius plot for Na+/K+ ATPase activity indicated a breakpoint at 8.6 °C, below which greater activation energy was required for the Na+/K+ ATPase reaction. Increased gill Na+/K+ ATPase temperature sensitivity below 8.6 °C may limit the ability of age-0 red drum to maintain ionic and osmotic balance during acute exposure to extreme cold temperatures.