Effects of seawater salinity and pH on cellular metabolism and enzyme activities in biomineralizing tissues of marine bivalves

Temperature but not ocean acidification affects energy metabolism and enzyme activities in the blue mussel,Mytilus edulis

“…CA activity remained unchanged in response to OA in mantle edge of M. edulis. Previous studies have shown variable CA responses to OA in bivalves including mussels (Ivanina et al, 2020).…”

“…Mantle edge tissue was homogenized and activities of Ca 2+ -ATPase (EC 3.6.3.8) and H + -ATPase (EC 3.6.3.6) was assayed as described in Ivanina et al, 2020. Inorganic phosphate (Pi) was measured using malachite green assay kit (ab65622, Abcam) and ATPase activities were expressed as µmol of Pi µg protein -1 hr -1 .…”

“…As a consequence of maintaining acid−base balance, OA may change concentrations of H + , HCO3 -Ca 2+ , Mg 2+ , and Cl − in calcifiers (Fitzer et al, 2014;Ramesh et al, 2017). Ion transport is an important contributor to energy budget of biomineralization because Ca 2+ transport and removal of excess protons from the site of biomineralization are ATP-dependent (Ivanina et al, 2020). In GOM mussels, activity of H + -ATPase and Ca 2+ -ATPase-in the mantle remained stable under moderate warming and OA (except for a modest but significant decline in Ca 2+ -ATPase under OWA).…”

“…Elevated PCO2 shifts the acid-base balance of organisms (Melzner et al, 2009) and most calcifiers have limited capacity to counteract OA-induced extracellular acidosis (Pörtner, 2008). This in turn can increase the energy costs to maintain cellular and organismal homeostasis in animals (Ivanina et al, 2020;Pörtner, 2008;Sokolova et al, 2012;Stapp et al, 2018;Stumpp et al, 2012) .…”

Decoupling salinity and carbonate chemistry: Low calcium ion concentration rather than salinity limits calcification in Baltic Sea mussels

“…At a cellular level, low seawater Ca 2+ availability may impact calcification by reduced rates of calcium transport across the mantle epithelia by plasma membrane Ca 2+ ATPases (PMCAs) (Niggli, 1982;McConnaughey and Whelan, 1997). Although PMCA activity and gene expression has not been shown to be impacted by salinity in Mercenaria mercenaria and Crassoestrea gigas, respectively, actual rates of Ca 2+ transport across the mantle epithelia have been shown to decrease at salinities of 14 compared to 28 in C. gigas (Ivanina, et al, 2020;Sillanpää, et al, 2020). This suggests that the reduced calcification rates observed in this study at low [Ca 2+ ] may stem from a reduced supply of Ca 2+ to the calcification site.…”