Calcification, a physiological process to be considered in the context of the whole organism

Abstract

Abstract. Marine organisms that produce calcium carbonate structures are predicted to be most vulnerable to a decline in oceanic pH (ocean acidification) based on the understanding that calcification rates will decrease as a result of changes in the seawater carbonate chemistry thereby reducing carbonate ion concentration (and associated saturation states). Coastal seas are critical components of the global carbon cycle yet little research has been conducted on acidification impacts on coastal benthic organisms. Here, a critical appraisal of calcification in six benthic species showed, contrary to popular predictions, calcification can increase, and not decrease, in acidified seawater. Measuring the changes in calcium in isolated calcium carbonate structure as well as structures from live animals exposed to acidified seawater allowed a comparison between a species' ability to calcify and the dissolution affects across decreasing levels of pH. Calcium carbonate production is dependant on the ability to increase calcification thus counteracting an increase in dissolution. Comparison with paleoecological studies of past high carbon dioxide (CO2) events presents a similar picture. This conclusion implies that calcification may not be the critical process impacted by ocean acidification; particularly as all species investigated displayed physiological trade offs including reduced metabolism, health, and behavioural responses, in association with this calcification upregulation, which possess as great a threat to survival as an inability to calcify.

Towards a meaningful assessment of marine ecological impacts in life cycle assessment (LCA)

“…Counter-intuitive results are also found: several studies have shown increased calcification rates under reduced pH (Wood et al, 2008;Findlay et al, 2009). This has been attributed to up-regulation of calcification rates at the expense of other physiological processes, such as metabolic rates (Findlay et al, 2009).…”

“…This has been attributed to up-regulation of calcification rates at the expense of other physiological processes, such as metabolic rates (Findlay et al, 2009). Also, ocean acidification has been shown to positively affect carbon fixation rates in some calcifying photosynthetic organisms (Kroeker et al, 2010;Pandolfi et al, 2011;Ries et al, 2009).…”

Calcification and inducible defence response of a calcifying organism could be maintained under hypoxia through phenotypic plasticity

“…Since calcification is an energy-demanding process (Palmer, 1992), the impaired aerobic metabolism under hypoxia could be the underlying mechanism causing the reduced calcification as previously observed (e.g. Cheung et al, 2008;Findlay et al, 2009;Wijgerde et al, 2014).…”

Changing mineralogical properties of shells may help minimize the impact of hypoxia-induced metabolic depression on calcification

“…It has been suggested that carbonate saturation state does not necessarily influence calcification since calcifying organisms may be able to use bicarbonate ions for this process (Ries, 2011a;Bach, 2015). Instead, growing evidence reveals that calcification is mainly driven by the energy metabolism of calcifying organisms since this process is energy-dependent (Findlay et al, 2009;Wijgerde et al, 2014).…”