Table 4. Summary of some studies examining the effect of pH on abalone physiology

Species Stressor levels and duration Duration Parameters General findings References
Pacific abalone (Haliotis discus hannai) pH 7.3, 7.6, 7.9, and 8.2 (control). Eggs: 15 hHatched larvae: 48 h Hatching rate and time, shell length, malformation and metamophosis rate. Reductions of 0.6–0.9 units in pH level had a negative impact on abalone early development. Li et al., 2013
Donkey ear’s abalone (Haliotis asinina) pH 8.15, 7.85, and 7.65 24 h Shell length and malformation rate. Shell length decreases and malformation increases at low pH. Santander-De Leon & Sayno, 2018
European abalone (Haliotis tuberculata) pH 8.0 (460 µatm pCO2, control) and 7.7 (1,000 µatm pCO2) 5 mon Survival, growth, phagocytosis, pHT of hemolymph, metabolism, gene expression, shell strength, nano-indentation measurements, SEM. The hemolymph pH was reduced. Immunity and metabolism were not impacted. Mechanical characteristics, calcification, and shell growth were all negatively impacted. Avignon et al., 2020
European abalone (Haliotis tuberculata) pH 7.9, 7.7, and 7.4 15 d Survival and growth, Hemolymph pH, total alkalinity, pCO2, HCO3, Saturation state (Ω), and total protein content of hemolymph. Survival, growth, and protein content were not significantly different. The other parameters were reduced at pH 7.4. Auzoux-Bordenave et al., 2021
European abalone (Haliotis tuberculata) pH 8.0 (control) and 7.7 5 d Hatching rate, % swimming larvae, malformation rate, shell length, shell birefringence, SEM, swimming behavior, respiration rate, and larval settlement. Low pH significantly impacts the shell and tissue formation, shell length, and birefringence. Kavousi et al., 2022
Pacific abalone (Haliotis discus hannai) and Many-colored abalone (Haliotis diversicolor) 560 μatm (control), 880 μatm (pH 7.9) and 1,600 μatm (pH 7.7). 1 y Shell surface, growth, crushing force, microstructure, hardness, composition, and Calcium carbonate (CaCO3) morphology. Ocean acidification (OA) altered many-colored abalone shell CaCO₃ morphology, microstructure, and hardness, reducing shell breaking force. Pacific abalone had unchanged CaCO₃ morphology and microstructure, and OA did not diminish nacre layer hardness. Due to reduced calcification, shell resistance to crushing force was still inadequate. Guo et al., 2023
Pacific abalone (Haliotis discus hannai) pH 8.1 and 7.5 combination with temperature 15°C, 20°C, and 25°C 5 d Hemolymph H2O2 and MDA level, gene expression of CAT, SOD, and caspase-3 in hepatopancreas, in situ hybridization for SOD mRNA expression, and apoptosis level in the hepatopancreas. H2O2, MDA, SOD, CAT, and caspase-3 increased at low pH and/or low/high water temperature. Apoptosis level was also high at high temperatures and low pH. Kim et al., 2023
SEM, scanning electron microscope; CAT, catalase; SOD, superoxide dismustase; MDA, Malondialdehyde.