Furthermore, there are several reports showing that calcification is improved in today's less alkaline/high CO2 conditions in tested calcifiers. Experiments showing that ocean "acidification" is damaging to calcifiers have all used experimental pH levels that are not projected to be reached in the oceans until the next century. In this review we assess the evidence concerning both criticisms and find that both are scientific myths. (ii) The biological calcification reaction that precipitates CaCO3 crystals into the shells is itself "…the major way by which CO2 is returned to the atmosphere". Two criticisms are made about the use of this straightforward biotechnology as a carbon sequestration tool: (i) ocean acidification which has already occurred has allegedly been shown to cause reduced shell formation in calcifiers. Consequently, these organisms could serve as a biotechnological carbon capture and storage mechanism, contributing to control of climate change.
Today's marine calcifiers (coccolithophore algae, Foraminifera (protists), Mollusca, Crustacea, corals) remove carbon dioxide (CO2) from the atmosphere, converting it into solid calcium carbonate (CaCO3) which is stable for geological periods of time. Finally, important bias in research efforts included most experiments on adult corals (68.5%), in 27 out of 150 (18%) coral ecoregions and exclusively from shallow-waters. The diversity in experimental designs prevented deciphering the modulating role of coral life stages, genera or duration of exposure. When exposed to pH 7.6-7.8 (compared to higher pH), 49% of endpoints were affected. The relative number of affected endpoints increased with pH intensity (particularly for endpoints associated to calcification and reproduction).
We identified 141 articles (published between 19) and separated endpoints into 22 biological categories to identify global trends for mitigation and gaps in knowledge and research priorities for future investigators. This review aimed at synthesizing the literature on the effects of seawater acidification on tropical scleractinians under laboratory-controlled conditions. Ocean acidification has emerged as a major concern in the last fifteen years and studies on the impacts of seawater acidification on marine organisms have multiplied accordingly.
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