Accumulated carbon dioxide in the atmosphere is one of the driving factors in ocean acidification as oceanic absorption of carbon dioxide alters ocean chemistry. Lower concentrations of carbonate ions and higher concentrations of hydrogen ions in the water adversely affect marine organisms, including sea urchin larvae, that use calcium carbonate in their skeletal structures. While there is a wide body of literature demonstrating an impact of lowered pH on sea urchin larval development and survival, it is unclear if the method of pH manipulation and the species being studied influences the results. To address this, we compared two commonly employed pH manipulation methods, hydrochloric acid addition and carbon dioxide bubbling, for impacts on sea urchin development in Lytechinus variegatus. We also compared the effects of projected acidic ocean pH on larval development in L. variegatus and Arbacia punctulata. Regardless of species and pH manipulation method survivorship and aspects of skeletal features decreased as pH decreased. Counts of developmental abnormalities increased with decreasing pH. However, changes in size of specific skeletal features and prevalence of types of abnormalities observed varied with both pH manipulation method and species. Our results are consistent with previous studies showing a decrease in survivorship and skeletal size with lowered pH but indicate that the methods used to study effects of acidification on sea urchin larval development can affect the experimental outcomes and hinder making broad conclusions.


We would like to acknowledge S. Ashcraft for help with this project. We would also like to acknowledge funding given to E. Pace from a USG STEMIV grant and grant from the John and Mary Franklin foundation awarded to J. Leyba.

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