Impact of seawater carbonate chemistry on the calcification of marine bivalves

Abstract

Abstract. Bivalve calcification, particularly of the early larval stages, is highly sensitive to the change in ocean carbonate chemistry resulting from atmospheric CO2 uptake. Earlier studies suggested that declining seawater [CO32−] and thereby lowered carbonate saturation affect shell production. However, disturbances of physiological processes such as acid-base regulation by adverse seawater pCO2 and pH can affect calcification in a secondary fashion. In order to determine the exact carbonate system component by which growth and calcification are affected it is necessary to utilize more complex carbonate chemistry manipulations. As single factors, pCO2 had no effects and [HCO3-] and pH had only limited effects on shell growth, while lowered [CO32−] strongly impacted calcification. Dissolved inorganic carbon (CT) limiting conditions led to strong reductions in calcification, despite high [CO32−], indicating that [HCO3-] rather than [CO32−] is the inorganic carbon source utilized for calcification by mytilid mussels. However, as the ratio [HCO3-] / [H+] is linearly correlated with [CO32−] it is not possible to differentiate between these under natural seawater conditions. An equivalent of about 80 μmol kg−1 [CO32−] is required to saturate inorganic carbon supply for calcification in bivalves. Below this threshold biomineralization rates rapidly decline. A comparison of literature data available for larvae and juvenile mussels and oysters originating from habitats differing substantially with respect to prevailing carbonate chemistry conditions revealed similar response curves. This suggests that the mechanisms which determine sensitivity of calcification in this group are highly conserved. The higher sensitivity of larval calcification seems to primarily result from the much higher relative calcification rates in early life stages. In order to reveal and understand the mechanisms that limit or facilitate adaptation to future ocean acidification, it is necessary to better understand the physiological processes and their underlying genetics that govern inorganic carbon assimilation for calcification.

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

“…This optimumcurve response pattern was explained by the interaction between HCO − 3 and protons (H + ), where HCO − 3 stimulates calcification as substrate and H + functions as inhibitor (Bach et al, 2011(Bach et al, , 2013. Similar conclusions have also been made in studies with bivalves (Thomsen et al, 2015) and corals (Jury et al, 2010), where it has been noted that the calcification response to changing carbonate chemistry could be the result of the opposing effects of and [H + ]. Jokiel (2011aJokiel ( , b, 2013 Jokiel, 2013;Jokiel et al, 2014).…”

“…A variety of studies highlighted that carbonate chemistry controls calcification through the balance of stimulation by an inorganic carbon substrate (HCO − 3 or DIC) and inhibition by protons (e.g., Bach et al, 2011;Jokiel 2011a;Thomsen et al, 2015). Other studies found that [CO 2− 3 ] or CaCO 3 are the carbonate-chemistry parameters which best predict calcification (e.g., Schneider and Erez, 2006;de Putron et al, 2011;Gazeau et al, 2011;Waldbusser et al, 2014) (9) and (12) Jokiel, 2011aJokiel, , b, 2013Jokiel et al, 2014), which are arguably the physiologically more meaningful parameters to correlate gross calcification with (Bach et al, 2013;Jokiel, 2013;Thomsen et al, 2015;Sects.…”

Persistent spatial structuring of coastal ocean acidification in the California Current System

“…While pH is a fundamental property of the carbonate system, OA can also affect organism performance through p CO 2 , HCO 3 − , and/or CO 3 2– dependent pathways 25–27 . In the CCLME, aragonite saturation state ( Ω arag ) has emerged as a highly predictive parameter for linking carbonate chemistry change to biological impacts in a number of important taxa 5, 27, 28 .…”

Seasonal variation in aragonite saturation in surface waters of Puget Sound – a pilot study

“…This condition is often described as "corrosive" (e.g., Feely et al, 2010). Recent laboratory studies indicate that impacts on sensitive species can occur at higher aragonite saturation states as organisms expend additional energy during early life stages (e.g., Thomsen et al, 2015;Waldbusser et al, 2015b). In general, surface waters of the open ocean are typically super-saturated with respect to aragonite (Ω arag > 1; e.g., Feely et al, 2009).…”