The Effects of Ocean Acidification on the Development and Calcification of the Larval Shells of the Red Abalone Haliotis rufescens Swainson, 1822

This study focuses on the effects of increasing atmospheric carbon dioxide and decreasing pH on the development and calcification of larval red abalone shells. Experimental bowls were inoculated with 2 mL of a homogenous mixture of red abalone embryos. Six replicate bowls were placed inside each of four plexiglass gas chambers: a control chamber injected with 200 cc of air, a chamber injected with 200 cc of 10% CO₂, another injected with 400 cc of 10% CO₂, and a fourth chamber injected with 600 cc of 10% CO₂. After 48 hours, the chambers were opened, and the abalone larvae were transferred into culture flasks, fixed with formalin, and examined under an inverted compound microscope. Statistically significant differences between the treatments (increasing levels of CO₂ and decreasing pH) on red abalone shell development and calcification were observed even at the lowest volume of CO₂ injected (i.e., 200 cc of CO₂).

These results strongly suggest that increasing levels of CO₂ and decreasing levels of pH result in abnormal abalone larval development. The results also support the use of CO₂ injection into gas chambers to mimic the real-life processes of ocean acidification and the use of the EPA-approved red abalone chronic toxicity test protocol, which is typically used to assess toxicity of sewage and treated sewage (effluent), as an appropriate method for investigating the effects of ocean acidification on the larval development of the abalone.