title: The influence of calcium on the physiological responses of the rainbow trout, Salmo gairdneri, to low environmental pH.
abstract: The physiological responses of 1- to 2-year-old rainbow trout to low pH are dependent on the environmental calcium concentration. Trout, maintained for 5 days in moderately hard water ([Ca2+] = 1.6-2.7 m-equiv/l) at a mean pH of 4.3, developed a major blood acidosis but exhibited only a minor depression in plasma ion levels. In acidified soft water ([Ca2+] = 0.3 m-equiv/l), only a minor acidosis occurred, but plasma ion levels fell and there were substantially greater mortalities. Lethal bioassays performed on fingerling trout over a range of pH levels (3.0-4.8) revealed an important influence of external [Ca2+] on resistance to acid exposure. Terminal physiological measurements on adult fish succumbing to low pH in soft water indicate the singular importance of iono-regulatory failure as the toxic mechanism of action under these circumstances.
mesh_terms: D000136:Acid-Base Equilibrium / Q000187:drug effects; D000222:Adaptation, Physiological; D000693:Anaerobiosis; D000818:Animals; D001810:Blood Volume; D002118:Calcium / Q000494:pharmacology*; D004734:Energy Metabolism; D005618:Fresh Water; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000097:blood; D012487:Salmonidae / Q000502:physiology*; D014337:Trout / Q000502:physiology*; D014882:Water-Electrolyte Balance / Q000187:drug effects
chemical_list: D010100:Oxygen; D002118:Calcium