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Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCover“Sea hares” such as the Aplysia punctata (Cuvier, 1803) specimen from Yorkshire, England, pictured on the cover, are coastal marine gastropods that have distinctive, pointed rhinophores that resemble the ears of terrestrial hares. Its congener A. californica is a model organism for neurobiology. All marine species, Aplysia included, face challenges from climate warming and ocean acidification, the process of decreasing seawater pH caused by increased levels of dissolved atmospheric CO2. One of the most prominent potential impacts of ocean acidification is that lower seawater pH will weaken calcium carbonate shells through dissolution, or increase the energy required to build and maintain them. Ocean acidification has also been shown to cause changes in the metabolic rates of many marine species, with further implications for the energetics of building and maintaining shells.On pages 142–151 of this issue, Nicholas Carey, Sam Dupont, and Julia Sigwart, in the first study of the effects of ocean acidification in sea hares, report the effects of extreme low pH on metabolism and shell calcification in A. punctata. They determined that low pH caused metabolic depression in these species, at least in the short term. But despite the low pH conditions, there was no impact on calcification in its internal shell. In the mollusc, shell growth occurs in two stages; first, a proteinaceous matrix is laid down, and then calcification occurs within this scaffolding, as long as acid-base balance is maintained by the animal. However, there was evidence that the lower metabolic rates resulted in reduced growth of the proteinaceous matrix, which would eventually result in reduced overall shell growth.The results of this work suggest that the prominence given to impacts of ocean acidification upon calcification may be overstated; the ability of marine invertebrates to maintain the proper conditions for calcification may be more common than previously thought. Calcification can occur even under extreme low pH conditions, as long as the supporting matrix is present. Instead, future studies should consider the overall impacts of ocean acidification on the energetics of calcifying organisms; impacts to shell growth may be due to energetic constraints, rather than the common perception of an acidic ocean dissolving away the shells of marine organisms.Credits: Photo, © Ian F. Smith, http://bit.ly/aplysia; cover design: LianneDunn.com Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 231, Number 2October 2016 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/690097 © 2016 by Marine Biological Laboratory. All rights reserved.PDF download Crossref reports no articles citing this article.