Exploring aberrant bivalve shell ultrastructure and geochemistry as proxies for past sea water acidification
Exploring aberrant bivalve shell ultrastructure and geochemistry as proxies for past sea water acidification
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DOI：
10.1111/sed.12107
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发表时间：
2014-10-01
期刊：
影响因子：
3.5
通讯作者：
Immenhauser, Adrian
中科院分区：
文献类型：
--
作者：
Hahn, Sabine;Griesshaber, Erika;Immenhauser, Adrian
纵观地球的大部分历史，海洋碳酸盐代表了环境变化的最重要的地质档案之一。显生宙期间的几个关键事件，如大灭绝或过热事件，最近被认为与海洋酸化有关。然而，对于过去的海洋酸化事件来说，定义明确的地质代用物，充其量是稀缺的。本实验探讨了双壳类动物的超微结构和同位素地球化学（C-13、O-18和Mg-26）对应激环境的响应，特别是对海水酸化的响应。在本研究中，对普通蓝贻贝（Mytilus edulis）在4种pH（pH(NBS) 72至pH 80）条件下（从幼年早期到1岁）进行了培养。比较了不同处理的贝壳生长速率和主要钙化部分的超微结构。暴露在低ph环境下的标本显示，在结构良好的外壳中，有一块块无序的钙质纤维取向。此外，电子背散射衍射分析表明，在酸化条件下，方解石棱镜的c轴呈现双峰或多峰分布模式。据报道，在自然酸化的海水条件下保存的足脂虫也有类似的外壳紊乱模式。相比之下，本研究发现没有证据表明不同的pH值制度会影响壳的碳、氧或镁同位素比率。基于这些观察结果，我们提出：(1)压力环境，在这种情况下，低海水pH，可预测地影响双壳类生物矿化模式；（ii）这些发现有可能作为古代海水酸化的新（岩石学）代用物。评估这些数据对来自选定时间间隔的保存完好的化石壳材料的适用性需要额外的工作。
Throughout much of Earth's history, marine carbonates have represented one of the most important geological archives of environmental change. Several pivotal events during the Phanerozoic, such as mass extinctions or hyperthermal events have recently been associated with ocean acidification. Nevertheless, well-defined geological proxies for past ocean acidification events are, at best, scarce. Here, experimental work explores the response of bivalve shell ultrastructure and isotope geochemistry (C-13, O-18 and Mg-26) to stressful environments, in particular to sea water acidification. In this study, the common blue mussel, Mytilus edulis, was cultured (from early juvenile stages to one year of age) at four pH regimes (pH(NBS) 72 to pH 80). Shell growth rate and ultrastructure of mainly the calcitic portion of the shells were compared between experimental treatments. Specimens exposed to low-pH environments show patches of disordered calcitic fibre orientation in otherwise well-structured shells. Furthermore, the electron backscattered diffraction analyses reveal that, under acidified conditions, the c-axis of the calcite prisms exhibits a bimodal or multi-modal distribution pattern. Similar shell disorder patterns have been reported from mytilids kept under naturally acidified sea water conditions. In contrast, this study found no evidence that different pH regimes affect shell carbon, oxygen or magnesium isotope ratios. Based on these observations, it is proposed that: (i) stressful environments, in this case low sea water pH, predictably affect bivalve biomineralization patterns; and (ii) these findings bear potential as a novel (petrographic) proxy for ancient sea water acidification. An assessment of the applicability of these data to well-preserved fossil shell material from selected time intervals requires additional work.