Dolomite-rich coralline algae in reefs resist dissolution in acidified conditions

TitleDolomite-rich coralline algae in reefs resist dissolution in acidified conditions
Publication TypeJournal Article
Year of Publication2013
AuthorsNash MC, Opdyke BN, Troitzsch U, Russell BD, Adey WH, Kato A, Diaz-Pulido G, Brent C, Gardner M, Prichard J, Kline DI
JournalNature Climate Change
Date Published2013/03
Type of ArticleArticle
ISBN Number1758-678X
Accession NumberWOS:000319399000023
Keywordscarbonates; magnesian calcites; nucleation; ocean acidification; polysaccharide; productivity; turbulent

Coral reef ecosystems develop best in high-flow environments but their fragile frameworks are also vulnerable to high wave energy. Wave-resistant algal rims, predominantly made up of the crustose coralline algae (CCA) Porolithon onkodes and P. pachydermum(1,2), are therefore critical structural elements for the survival of many shallow coral reefs. Concerns are growing about the susceptibility of CCA to ocean acidification because CCA Mg-calcite skeletons are more susceptible to dissolution under low pH conditions than coral aragonite skeletons(3). However, the recent discovery(4) of dolomite (Mg0.5Ca0.5(CO3)), a stable carbonate(5), in P. onkodes cells necessitates a reappraisal of the impacts of ocean acidification on these CCA. Here we show, using a dissolution experiment, that dried dolomite-rich CCA have 6-10 times lower rates of dissolution than predominantly Mg-calcite CCA in both high-CO2 (similar to 700 ppm) and control (similar to 380 ppm) environments, respectively. We reveal this stabilizing mechanism to be a combination of reduced porosity due to dolomite infilling and selective dissolution of other carbonate minerals. Physical break-up proceeds by dissolution of Mg-calcite walls until the dolomitized cell eventually drops out intact. Dolomite-rich CCA frameworks are common in shallow coral reefs globally and our results suggest that it is likely that they will continue to provide protection and stability for coral reef frameworks as CO2 rises.

Short TitleNat. Clim. Chang.
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