Effects of temperature and carbon dioxide on green sturgeon blood-oxygen equilibria

There are three Northeast Pacific Rivers still supporting spawning populations of green sturgeon, Acipenser medirostris, but all have been modified hydrologically and thermally by dam construction. Age 1- to 3-year-old green sturgeon, progeny of artificially spawned, wild-caught Klamath River adults, were used to assess the effects of temperature and carbon dioxide on critical hematological parameters related to evolutionary adaptations of this species to its physical environment. In vitro measurement of the effect of temperature and carbon dioxide on blood-oxygen affinity and equilibrium curve shape yielded the following data for the respective temperature treatments (11, 15, 19, and 24 degrees C): half-saturation values (P-50's, kPa, a measure of affinity) 1.26, 1.44, 1.63, 1.69 for low-PCO2 treatments and 2.08, 2.41, 2.74, 2.94 for high-PCO2 treatments; Bohr factors -0.322, -0.327, -0.366, -0.536; and non-bicarbonate buffer values (slykes) -6, -3, -5, -8. Temperature sensitivities (Delta H, kJ mol O-2(-1)) between these respective temperatures were -34.20, -15.24, -6.74 for low-PCO2 treatments and -20.05, -27.00, and -11.55 for the high-PCO2 treatments. These data suggest that juvenile green sturgeon may tolerate moderate environmental hypoxia, moderate aerobic activity, low to moderate hypercapnia, and moderate temperature changes in their environments.