Figure 4

The relationship between net ammonia flux rates (J^Amm_net) and unidirectional Na⁺ uptake rates (J^Na_in) of adult zebrafish in different exposure conditions in ion-poor water (IPW).

Means ± 1 SEM. Gray circles represents flux rates of both J^Amm_net and J^Na_in of zebrafish under the acclimation conditions (i.e. IPW – pH 7.0 or IPW + DOC – pH7.0; 0–3 h) and then acutely exposed to either IPW + DOC – pH 7.0, or IPW – pH 4.0 or IPW + DOC – pH 4.0 (3–6 h), followed by a recovery period in which they were again exposed to their acclimation condition (IPW – pH 7.0 or IPW + DOC – pH 7.0). Note that the two black circles (not used in the regression) represent data from fish acutely exposed to IPW – pH 4.0 (no DOC) and these same fish during the recovery period at IPW – pH 7.0, where J^Amm_net was entirely uncoupled from J^Na_in. Nonlinear regression analysis was performed using Sigma Plot v 11.0. r² = 0.639; p = 0.001, F = 19.531.