Abstract
Ocean acidification is expected to negatively impact many calcifying marine organisms by impairing their ability to build their protective shells and skeletons, and by causing dissolution and erosion. Here we investigated the large predatory ‘Triton shell’ gastropod Charonia lampas in acidified conditions near CO2 seeps off Shikine-jima (Japan) and compared them with individuals from an adjacent bay with seawater pH at present-day levels (outside the influence of the CO2 seep). By using computed tomography we show that acidification negatively impacts their thickness, density and shell structure, causing visible deterioration to the shell surface. Periods of aragonite undersaturation caused the loss of the apex region, exposing body tissues. While gross calcification rates were likely reduced near CO2 seeps, the corrosive effects of acidification were far more pronounced around the oldest parts of the shell. As a result, the capacity of C. lampas to maintain their shells under ocean acidification may be strongly driven by abiotic dissolution and erosion, and not under biological control of the calcification process. Understanding the response of marine calcifying organisms and their ability to build and maintain their protective shells and skeletons will be important for our understanding of future marine ecosystems.
Highlights
Surface seawater is being altered due to increasing atmospheric carbon dioxide (CO2) concentrations, causing reductions in pH, carbonate ions [CO32−], and saturation states ( ) of calcium carbonate minerals (Raven et al, 2005; IPCC, 2013)
As calcifying organisms are a fundamental component of coastal marine communities, the effects of ocean acidification are expected to lead to profound ecological shifts (Hall-Spencer et al, 2008; Harvey et al, 2014; Nagelkerken and Connell, 2015; Sunday et al, 2017)
Organisms with calcium carbonate shells or skeletons appear to be the most vulnerable to increasing levels of seawater pCO2 (Harvey et al, 2013) and understanding their response is critical to assessments of the effects of rapidly falling carbonate saturation levels in coastal ecosystems
Summary
Surface seawater is being altered due to increasing atmospheric carbon dioxide (CO2) concentrations, causing reductions in pH, carbonate ions [CO32−], and saturation states ( ) of calcium carbonate minerals (Raven et al, 2005; IPCC, 2013) This fundamental change to sea water chemistry is termed ocean acidification (Caldeira and Wickett, 2003) and can make seawater corrosive to carbonates. Over this century, many calcifying marine organisms may be negatively impacted by ocean acidification as it is expected to impair their ability to build and maintain protective shells and skeletons (Harvey et al, 2013; Kroeker et al, 2013; Gattuso et al, 2015). It is thought that the effects of ocean acidification on calcification are not an issue of [CO32−] substrate limitation (Bach, 2015; Cyronak et al, 2016; Waldbusser et al, 2016); instead representing a physiological constraint
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