Effect of pH on growth rate, oxygen consumption rate, and histopathology of gill and kidney tissue for juvenile greenlip abalone, Haliotis laevigata donovan and blacklip abalone, Haliotis rubra leach

Juvenile greenlip abalone, Haliotis laevigata, (mean whole mass 2.30 ± 0.73 g, mean ± SD, n = 561) and juvenile blacklip abalone, Haliotis rubra, (mean whole mass 1.56 ± 0.64 g, mean ± SD, n = 559) were grown for 50-68 days in bioassay tanks at a range of pH levels adjusted using hydrochloric acid (HCl) or sodium hydroxide (NaOH). For greenlip abalone, specific growth rate (SGR) was significantly affected by pH, whether measured on a length or whole mass basis (P < .001). For blacklip abalone, SGR was significantly affected by pH whether SGR was measured on a length or whole mass basis. For growth, expressed on a whole mass basis, the EC₅ values (5% growth reductions) were at pH 7.78 and 8.77 for greenlip abalone, and at 7.93 and 8.46 for blacklip abalone. The EC₅₀ values (50% growth reductions) were at pH 7.39 for greenlip abalone, and 7.37 and 9.02 for blacklip abalone. Survival of both species was significantly reduced at pH 6.79, and survival of blacklip abalone was also significantly reduced at pH 7.76. At the end of the bioassay, groups of abalone were transferred to respiratory chambers. A significant reduction in respiratory activity was observed at both high and low pH values for greenlip abalone (P < .001). Greenlip abalone exposed to pH 7.16 showed alterations in kidney definition, tubule and lumen size, and an increase in gill hyperplasia and abnormalities. Blacklip abalone exposed to pH 7.16 demonstrated alterations to kidney and gill definition, and lumen size was increased.