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2016
Lebrato, M, Andersson AJ, Ries JB, Aronson RB, Lamare MD, Koeve W, Oschlies A, Iglesias-Rodriguez MD, Thatje S, Amsler M, Vos SC, Jones DOB, Ruhl HA, Gates AR, McClintock JB.  2016.  Benthic marine calcifiers coexist with CaCO3-undersaturated seawater worldwide. Global Biogeochemical Cycles. 30:1038-1053.   10.1002/2015GB005260   Abstract

Ocean acidification and decreasing seawater saturation state with respect to calcium carbonate (CaCO3) minerals have raised concerns about the consequences to marine organisms that build CaCO3 structures. A large proportion of benthic marine calcifiers incorporate Mg2+ into their skeletons (Mg-calcite), which, in general, reduces mineral stability. The relative vulnerability of some marine calcifiers to ocean acidification appears linked to the relative solubility of their shell or skeletal mineralogy, although some organisms have sophisticated mechanisms for constructing and maintaining their CaCO3 structures causing deviation from this dependence. Nevertheless, few studies consider seawater saturation state with respect to the actual Mg-calcite mineralogy (ΩMg-x) of a species when evaluating the effect of ocean acidification on that species. Here, a global dataset of skeletal mole % MgCO3 of benthic calcifiers and in situ environmental conditions spanning a depth range of 0 m (subtidal/neritic) to 5600 m (abyssal) was assembled to calculate in situ ΩMg-x. This analysis shows that 24% of the studied benthic calcifiers currently experience seawater mineral undersaturation (ΩMg-x < 1). As a result of ongoing anthropogenic ocean acidification over the next 200 to 3000 years, the predicted decrease in seawater mineral saturation will expose approximately 57% of all studied benthic calcifying species to seawater undersaturation. These observations reveal a surprisingly high proportion of benthic marine calcifiers exposed to seawater that is undersaturated with respect to their skeletal mineralogy, underscoring the importance of using species-specific seawater mineral saturation states when investigating the impact of CO2-induced ocean acidification on benthic marine calcification.

2011
Andersson, AJ, Mackenzie FT.  2011.  Technical comment on Kroeker et al. (2010) Meta-analysis reveals negative yet variable effects of ocean acidification on marine organisms. Ecology Letters, 13, 1419–1434. Ecology Letters. 14:E1-E2.: Blackwell Publishing Ltd   10.1111/j.1461-0248.2011.01646.x   AbstractWebsite

Meta-analysis of experimental results has been interpreted to imply that the calcification response of organisms depositing high Mg-calcite is more resilient to ocean acidification than organisms depositing aragonite/calcite. This conclusion might be biased by inadequate recognition and categorisation of high Mg-calcite according to mineral solubility.

2007
Andersson, AJ, Bates NR, Mackenzie FT.  2007.  Dissolution of carbonate sediments under rising pCO(2) and ocean acidification: Observations from Devil's Hole, Bermuda. Aquatic Geochemistry. 13:237-264.   10.1007/s10498-007-9018-8   AbstractWebsite

Rising atmospheric pCO(2) and ocean acidification originating from human activities could result in increased dissolution of metastable carbonate minerals in shallow-water marine sediments. In the present study, in situ dissolution of carbonate sedimentary particles in Devil's Hole, Bermuda, was observed during summer when thermally driven density stratification restricted mixing between the bottom water and the surface mixed layer and microbial decomposition of organic matter in the subthermocline layer produced pCO(2) levels similar to or higher than those levels anticipated by the end of the 21st century. Trends in both seawater chemistry and the composition of sediments in Devil's Hole indicate that Mg-calcite minerals are subject to selective dissolution under conditions of elevated pCO(2). The derived rates of dissolution based on observed changes in excess alkalinity and estimates of vertical eddy diffusion ranged from 0.2 mmol to 0.8 mmol CaCO3 m(-2) h(-1). On a yearly basis, this range corresponds to 175-701 g CaCO3 m(-2) year(-1); the latter rate is close to 50% of the estimate of the current average global coral reef calcification rate of about 1,500 g CaCO3 m(-2) year(-1). Considering a reduction in marine calcification of 40% by the year 2100, or 90% by 2300, as a result of surface ocean acidification, the combination of high rates of carbonate dissolution and reduced rates of calcification implies that coral reefs and other carbonate sediment environments within the 21st and following centuries could be subject to a net loss in carbonate material as a result of increasing pCO(2) arising from burning of fossil fuels.