Reconsidering the role of carbonate ion concentration in calcification by marine organisms

Abstract

Abstract. Marine organisms precipitate 0.5-2.0 Gt of carbon as calcium carbonate (CaCO 3 ) every year with a profound impact on global biogeochemical element cycles. Biotic calcification relies on calcium ions (Ca 2+ ) and usually on bicarbonate ions (HCO − 3 ) as CaCO 3 substrates and can be inhibited by high proton (H + ) concentrations. The seawater concentration of carbonate ions (CO 2− 3 ) and the CO 2− 3 -dependent CaCO 3 saturation state ( CaCO 3 ) seem to be irrelevant in this production process. Nevertheless, calcification rates and the success of calcifying organisms in the oceans often correlate surprisingly well with these two carbonate system parameters. This study addresses this dilemma through the rearrangement of carbonate system equations which revealed an important proportionality between [CO

H+ -driven increase in CO2 uptake and decrease in HCO3− uptake explain coccolithophores' acclimation responses to ocean acidification

“…F), is possibly that the uncertainties were larger than the effects. An interaction of a H + ‐driven decrease in calcification (as seen under acidification and OA ) and a ‐driven increase in calcification (as seen under carbonation ) explains the often observed pseudo‐correlation with the carbonate saturation state (Ω), which has been discussed recently (Bach ; Cyronak et al ; Rickaby et al ).…”

Echinometra sea urchins acclimatized to elevated pCO2 at volcanic vents outperform those under present‐day pCO2 conditions

“…In addition, using the relationship between test weight and test volume as a direct measure of the degree of calcification, we did not detect a difference in individuals between control and vent sites, despite the latter experiencing lower and occasionally undersaturated aragonite saturation states. While the degree of calcification in sea urchins has been related to aragonite saturation state in sea urchins, such as across latitudes (Watson et al ., ; Byrne et al ., ), a recent examination of the carbonate system suggests that calcification may not be directly related to aragonite saturation states, but to the [HCO −3 ]/[H + ] ratio (Bach, ). In addition to the external carbonate conditions, sea urchins have endoskeletons and therefore internal pH regulation may further drive independence of calcification from calcite saturations states.…”

Twenty Years of Marine Carbon Cycle Observations at Devils Hole Bermuda Provide Insights into Seasonal Hypoxia, Coral Reef Calcification, and Ocean Acidification

“…In other studies, bicarbonate ion concentration has been shown to be the primary modifier of coral calcification (e.g., Jury et al, 2010). The simplification of relationships between coral calcification and CO 2 -carbonate chemistry has many predictive uses and value for OA research (e.g., Kleypas et al, 1999;Orr et al, 2005;Dove et al, 2013;Evenhuis et al, 2015), but as Jokiel and others have pointed out (e.g., Jokiel et al, 2008;Jokiel, 2011aJokiel, ,b, 2016Comeau et al, 2013;Andersson et al, 2014;Bach, 2015), there may not be simple relationships or thresholds in ocean chemistry that are insightful for future projections.…”