Data from: Ocean acidification and temperature increase impacts mussel shell shape and thickness: problematic for protection?

Ocean acidification threatens organisms that produce calcium carbonate shells by potentially generating an under-saturated carbonate environment. Resultant reduced calcification and growth, and subsequent dissolution of exoskeletons, would raise concerns over the ability of the shell to provide protection for the marine organism under ocean acidification and increased temperatures. We examined the impact of combined ocean acidification and temperature increase on shell formation of the economically important edible mussel Mytilus edulis. Shell growth and thickness along with a shell thickness index and shape analysis were determined. The ability of M. edulis to produce a functional protective shell after 9 months of experimental culture under ocean acidification and increasing temperatures (380, 550, 750, 1000 μatm pCO2, and 750, 1000 μatm pCO2 + 2°C) was assessed. Mussel shells grown under ocean acidification conditions displayed significant reductions in shell aragonite thickness, shell thickness index, and changes to shell shape (750, 1000 μatm pCO2) compared to those shells grown under ambient conditions (380 μatm pCO2). Ocean acidification resulted in rounder, flatter mussel shells with thinner aragonite layers likely to be more vulnerable to fracture under changing environments and predation. The changes in shape presented here could present a compensatory mechanism to enhance protection against predators and changing environments under ocean acidification when mussels are unable to grow thicker shells. Here, we present the first assessment of mussel shell shape to determine implications for functional protection under ocean acidification.

海洋酸化可通过形成碳酸盐不饱和环境，对分泌碳酸钙外壳的海洋生物构成威胁。由此引发的钙化作用与生长速率下降，以及后续外壳溶解现象，将引发学界对海洋酸化与升温情境下外壳能否为海洋生物提供有效防护能力的担忧。本研究针对海洋酸化与升温的联合胁迫，对具有重要经济价值的可食用贻贝（Mytilus edulis）的外壳形成过程展开了影响探究。研究测定了外壳的生长与厚度参数，同时计算了外壳厚度指数并开展了形态学分析。本研究评估了紫贻贝在海洋酸化与升温条件下（设置梯度为380、550、750、1000 μatm二氧化碳分压（pCO₂），以及750、1000 μatm pCO₂ + 2℃的实验组）经过9个月人工培育后，形成具备防护功能外壳的能力。与环境对照条件（380 μatm pCO₂）下培育的贻贝外壳相比，海洋酸化组培育的贻贝外壳出现了文石（aragonite）层厚度、外壳厚度指数的显著降低，同时外壳形态发生改变（对应750、1000 μatm pCO₂实验组）。海洋酸化会使贻贝外壳变得更趋圆扁，且文石层更薄，这类外壳在环境变化与捕食压力下更易发生破裂。当贻贝无法增厚外壳时，本研究观测到的形态变化可能是一种补偿机制，用于在海洋酸化情境下提升对捕食者与环境变化的防护能力。本研究首次通过分析贻贝外壳形态，探究其在海洋酸化情境下对防护功能的潜在影响。