AUTHOR=Alcantar Marina W. , Hetrick Jeff , Ramsay Jacqueline , Kelley Amanda L. 

TITLE=Examining the impacts of elevated, variable pCO2 on larval Pacific razor clams (Siliqua patula) in Alaska

JOURNAL=Frontiers in Marine Science

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2024.1253702

DOI=10.3389/fmars.2024.1253702

ISSN=2296-7745

ABSTRACT=<p>An increase in anthropogenic carbon dioxide is driving oceanic chemical shifts resulting in a long-term global decrease in ocean pH, colloquially termed ocean acidification (OA). Previous studies have demonstrated that OA can have negative physiological consequences for calcifying organisms, especially during early life-history stages. However, much of the previous research has focused on static exposure to future OA conditions, rather than variable exposure to elevated <italic>p</italic>CO<sub>2</sub>, which is more ecologically relevant for nearshore species. This study examines the effects of OA on embryonic and larval Pacific razor clams (<italic>Siliqua patula</italic>), a bivalve that produces a concretion during early shell development. Larvae were spawned and cultured over 28 days under three <italic>p</italic>CO<sub>2</sub> treatments: a static high <italic>p</italic>CO<sub>2</sub> of 867 μatm, a variable, diel <italic>p</italic>CO<sub>2</sub> of 357 to 867 μatm, and an ambient <italic>p</italic>CO<sub>2</sub> of 357 μatm. Our results indicate that the calcium carbonate polymorphism of the concretion phase of <italic>S. patula</italic> was amorphous calcium carbonate which transitioned to vaterite during the advanced D-veliger stage, with a final polymorphic shift to aragonite in adults, suggesting an increased vulnerability to dissolution under OA. However, exposure to elevated <italic>p</italic>CO<sub>2</sub> appeared to accelerate the transition of larval <italic>S. patula</italic> from the concretion stage of shell development to complete calcification. There was no significant impact of OA exposure to elevated or variable <italic>p</italic>CO<sub>2</sub> conditions on <italic>S. patula</italic> growth or HSP70 and calmodulin gene expression. This is the first experimental study examining the response of a concretion producing bivalve to future predicted OA conditions and has important implications for experimentation on larval mollusks and bivalve management.</p>