Ocean acidification (OA) and global warming present future challenges for shell producing organisms such as mussels through reduction in the carbonate available to produce shells in these and other valuable aquaculture species. Molluscs control their shell growth through biomineralisation, but the response of the mechanisms behind biomineralisation to OA conditions are relatively unknown. It is unclear how much carbon is taken into the shell from the environment compared to the uptake through the food source. Shell production is energetically costly to molluscs and metabolic processes and energetic partitioning may affect their ability to perform the underlying mechanisms of biomineralisation under OA. It is possible that additional food consumption might alleviate some impacts caused by acidification. We assessed the ability of extra feeding to alter the impacts of OA and increased temperatures on adult Mytilus edulis. Carbon isotopes (δ¹³C) were used to examine the change in biomineralisation pathway in mussels. OA did not alter the δ¹³C directly in separate analyses of the shell calcite and aragonite layers, mantle tissue and extrapallial fluid. However, ambient treatments with increased temperatures altered the mussel biomineralisation pathway in the shell calcite using CO₃²⁻ instead of HCO₃⁻ as the main source of carbon. The proportion of metabolic carbon uptake into the mussel shell calcite layer increased under OA, with additive effects when exposed to increased temperatures and extra feeding. The proportion of metabolic carbon uptake is higher (7%–11%) in the shell aragonite layer compared to calcite, under ambient treatments. OA initially reduced the metabolic carbon uptake into the shell aragonite, but after a period of 4-months with extra feeding, the mussels were able to adjust their metabolic carbon uptake to a level experienced under ambient treatments. This indicates that an abundance of food resources may enable changes in mussel biomineralisation pathways to compensate for any decrease in seawater inorganic carbon associated with OA. The impact of OA on phytoplankton varies from species to species, changing the structure of the community which could provide sufficient food resources to maintain metabolic carbon uptake for mussel shell growth. This study of δ¹³C isotopic values has identified changes in biomineralisation pathway relating to the mussel metabolic carbon uptake from their food source, with varying results for the aragonite and calcite shell polymorphs. The implications of these findings suggest that some bivalve species with different shell composites may cope better under OA than others, demanding further study into species-specific biomineralisation pathways.

海洋酸化（OA）和全球变暖通过减少这些和其他有价值的水产养殖物种可用于生产贝壳的碳酸盐，对贻贝等贝壳生产生物提出了未来的挑战。软体动物通过生物矿化作用来控制壳的生长，但是生物矿化作用背后的机制对OA条件的响应相对未知。与通过食物来源摄取相比，目前尚不清楚从环境中吸收多少碳。壳类生产对软体动物和代谢过程的能量消耗很高，而高能分配可能会影响它们在OA下执行生物矿化潜在机制的能力。食用额外的食物有可能减轻酸化引起的某些影响。食用菌。碳的同位素（δ ¹³ C）被用来研究在贻贝在生物矿化途径的变化。OA不改变δ ¹³在壳方解石和文石层，外套膜和extrapallial流体的单独分析直接℃。然而，随着增加的温度环境改变处理贻贝生物矿化途径在使用CO壳方解石₃ ^2-代替HCO ₃ ^-作为碳的主要来源。在OA下，贻贝壳方解石层中代谢碳的吸收比例增加，当暴露于升高的温度和额外的饲喂下时具有加和作用。在环境处理下，与方解石相比，壳文石层中代谢碳吸收的比例更高（7％–11％）。OA最初降低了壳文石的代谢碳吸收量，但经过4个月的额外摄食后，贻贝能够将其代谢碳吸收量调节至环境处理条件下的水平。这表明丰富的食物资源可能使贻贝生物矿化途径发生变化，以补偿与OA相关的海水无机碳的任何减少。OA对浮游植物的影响因物种而异，改变社区的结构，这可以提供足够的食物资源，以维持贻贝壳生长所需的代谢碳吸收。δ的研究¹³ C同位素值已确定了与食物中贻贝代谢碳的摄入有关的生物矿化途径的变化，文石和方解石壳多晶型物的结果各不相同。这些发现的含义表明，一些具有不同壳成分的双壳类物种在OA条件下可能比其他物种更好，因此需要对物种特异性生物矿化途径进行进一步研究。