The influence of gradual water acidification on the acid/base status and plasma hormone levels in carp

Abstract

Carp ( Cyprinus carpio ) fitted with arterial catheters were subjected to gradual water acidification (from pH 7.6 to 4.0 in 4 h), and then monitored for 48 h. The measured blood parameters showed little or no disturbance; there was no ionoregulatory disturbance, no hyperglycemia, increase in plasma lactate, hypoxemia, or swelling of red blood cells. Only a slight transient decrease of plasma pH was found. Plasma catecholamine levels remained at control level. The plasma cortisol concentration showed a transient increase, and was returned to the control level 24 h after beginning water acidification. Our results contrast with literature data on carp where exposure to pH 4.0 caused severe blood electrolyte disturbance. We conclude that the rate of water acidification (gradual in our study as compared to acute in the literature) rather than the pH level itself determines the early effects of water acidification.