Blood chemistry response to acid exposure in yellow perch (Perca flavescens): comparison of populations from naturally acidic and neutral environments
To test whether blood chemistry of an acid-tolerant fish species is affected by the history of environmental H$^\textrm+\$$ exposure, we studied blood acid-base, ion, and metabolite status in a population of yellow perch from a naturally acidic lake (acid-lake perch, ALP). Measurements were taken after 16 h of moderate swimming in either pH 4.0 or pH 7.8 water. Responses of ALP were compared with those of conspecifics from a circumneutral lake (neutral-lake perch, NLP) and from a slightly alkaline lake (hard-water-lake perch, HLP). In addition, results from fish exercised to exhaustion, or exercised and allowed to recover 6 h, are presented. The ALP maintained a higher base excess (BE) and  than conspecifics from neutral environments at pH 7.8, and ALP had higher BE and  levels atpH 4.0 than at pH 7. 8; in contrast, NLP and HLP had less BE and at low pH. The ALP had significantly lower plasma  than NLP or HLP, but apparent losses at pH 4.0 were similar among populations. Plasma  at pH 4.0 was similar in ALP and NLP, but higher in HLP. Exhaustive exercise at low pH favored the appearance of base deficit relative to blood lactate, whereas base deficit and blood lactate increases were similar at pH 7.8. Our results show that physiological responses to low pH are determined at the population level, that exposing yellow perch to low pH while swimming elicits many of the same physiological disturbances seen in less acid tolerant fish species, and that postexercise blood chemistry in yellow perch depends on environmental water chemistry.