Fig. 7. Enzyme activities for glutamine synthetase (GSase), ornithine transcarbamylase (OTCase), arginase and carbamoyl phosphate synthetase III (CPSase III) were measured in juvenile toadfish exposed to 0, 500 and 1000 µmol N l^–1 ammonia for 96 h. Data are presented as means + S.E.M. Juveniles were reared from eggs harvested in Biscayne Bay and were used within 1 week of yolk-sac absorption. OTCase was the only enzyme group with a significant difference (P<0.05) among ammonia treatments. The sample size was N=4 for all categories except for the OTCase control and 500 µmol N l^–1 treatment (N=6). Statistically different groupings (a,b) from the one-way ANOVA post-hoc analysis are presented above bars for each OUC enzyme. Note that CPSase III activity is expressed as nmol min^–1 g^–1 (y₂ axis).