Fig. 1. The effects of external injections of CO₂-enriched sea water (4 % CO₂; white symbols; N=11) or CO₂-free acidified sea water (pH 6.3; grey symbols; N=7) on cardiac output (_b) and cardiac frequency (fH) in dogfish (Squalus acanthias). The effects of (A) CO₂ or (B) acidified water are depicted as representative traces and as mean values (C). Control fish (black symbols; N=11) received bolus injections of sea water. The shaded box represents the 20 s period of injection. (D) The changes in fH (fH) at the 20 s time point. Data are shown as means +1 standard error of the mean (S.E.M.). An asterisk denotes a statistically significant difference from the final pre-injection value (time zero). A double dagger denotes a statistically significant difference from the control and low-pH seawater groups. C, control. 1 mmHg=0.133 kPa.

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