海洋地质与环境重点实验室知识库

贻贝广泛分布于深海冷泉、热液及近海环境，环境适应性较强。贻贝利用环境中的物质和能量进行新陈代谢生成碳酸钙矿物介壳，保护内部软体组织。贻贝介壳作为一种生物矿物，矿化过程受多种因素影响，可以敏感记录生存环境。前人研究焦点集中在生物矿化的机制及介壳的微观结构等方面，传统技术手段需要复杂的样品预处理，会对介壳造成损害。激光拉曼光谱技术作为一种特殊“分子指纹”光谱，其具备原位无损、无需样品预处理、多组分探测等优点，对物质结构分析具有独特的优势，非常适合贻贝介壳矿物的研究。本文利用共聚焦显微拉曼光谱仪对不同环境 (近海、冷泉、热液)中生存的贻贝介壳进行对比分析，基于拉曼光谱数据分析了不同环境中贻贝介壳矿物的显著变化，获得以下几点结论：

(1) 近海贻贝介壳成矿存在差别，矿物组成上紫贻贝 (Mytilus galloprovincialis)中出现有机质，三种贻贝的结晶度有差别。长偏顶蛤 (Modiolus elongatus)及远东偏顶蛤 (Modiolus kurilensis)介壳棱柱层为方解石，珍珠层为文石。紫贻贝棱柱层为方解石，珍珠层矿物主要为文石，生长区含方解石，且发现有机分子多烯，多烯的拉曼位移在1019、1131、1301、1519、2235和2635 cm⁻¹。多烯的拉曼信号强度与生长区的颜色有正比例关系。介壳中的有机质多烯与成矿密切相关。半峰宽大小反映结晶度变化，对三种贻贝介壳珍珠层文石的碳酸钙主峰1085 cm^-1半峰宽进行统计，紫贻贝最大生长方向及与其垂直方向的结晶度没有明显差别，个体间无差别。长偏顶蛤最大生长方向文石结晶度高于其垂直方向，个体间无明显差别。远东偏顶蛤整体结晶度高于青岛近海两种贻贝，最大生长方向文石结晶度高于其垂直方向，远东偏顶蛤的生存环境可能更有利于其介壳矿化。不同生长方向的结晶度不同，初步判断与生物大分子严格控制介壳成矿有关。

(2) 冷泉平端深海偏顶蛤(Bathymodiolus platifrons)介壳矿物以文石与方解石为主。采自台西南福尔摩沙脊冷泉区的平端深海偏顶蛤棱柱层矿物为方解石，珍珠层矿物为文石，两种矿物的拉曼位移与近海环境的贻贝无差别。碳酸钙主峰半峰宽与长偏顶蛤及紫贻贝相近，且最大生长方向结晶度比垂直方向结晶度高，贻贝个体间结晶度不同，初步判断与其所处生长阶段有关。平端深海偏顶蛤适应了深海冷泉环境，在甲烷浓度高的区域，贻贝介壳矿化与近海无明显区别。

(3) 热液环境对深海偏顶蛤介壳矿物有较为显著的影响。采自马努斯热液区的深海偏顶蛤(Bathymodiolus manusensis)棱柱层矿物为方解石，珍珠层为文石。贻贝珍珠层矿物的半峰宽比其他环境贻贝珍珠层大，个体间有显著差别。珍珠层文石结晶度比其他环境差，热液环境的复杂性与介壳成矿关系密切，深海热液温度梯度大，重金属离子种类多、浓度高，影响了偏顶蛤的生存，介壳矿化不稳定，矿物结晶度较其他海洋环境差。

Mussels are widely distributed in the deep-sea (cold springs and hydrothermal fields) and offshore areas because of their strong adaptabilities to these environments. Mussels consume materials and energies in the environments to sustain the metabolism and to secrete calcium carbonate minerals to form shells for protecting the soft tissues. As a biomineral, the mineral shell is sensitive to environments ,which results in the shells ideal subjects to study the physiochemical changes of their living environments during the formation processes. Generally, the previous researches mainly focus on the mechanism of the biomineralization processes and the microstructure of the shells, based on the traditional technical methods that require complex sample pretreatments, and cause damages to the shell samples. Here, we introduce laser Raman spectroscopy, a kind of "fingerprint" spectroscopy, to study the material structures of the shells. The laser Raman spectroscopy has many advantages, such as in-situ measurements, non-destructive to the samples, no need of sample pretreatment, and multi-component detection at a time, etc. Therefore, it is very suitable for the study of mussel shells minerals. In this paper, confocal micro-Raman spectroscopy was used to analyze and compare the mussel shells in different environments (offshore areas, cold seeps, hydrothermal fields). Based on the characteristics of the Raman spectra, significant changes in the minerals of mussel shells in different environments were revealed and the following conclusions are obtained:

(1) Differences exist in the mineralization of mussel shells of offshore areas. Organic matters appear in the shells of Mytilus galloprovincialis. The crystallinity of three mussel shells are different. The prism layers of the shells of the Modiolus elongatus and Modiolus kurilensis are calcite, while the nacre layers is composed of aragonite. The prism layer of Mytilus galloprovincialis in Qingdao-offshore is calcite, the nacre layer is dominated with aragonite. The growth area contains calcite, and the organic molecule polyene is found with the Raman shift at 1019, 1131, 1301, 1519、2235 and 2635 cm⁻¹. The polyene in the shell is closely related to mineralization and the Raman intensity directly proportional to the color of the growing area. The FWHM (full width at half maximum) of calcium carbonate at 1085 cm^-1 of three types of mussel shells nacre aragonite was counted. The FWHM reflects the change of crystallinity. No obvious differences between the maximum growth direction and the vertical crystallinity of Qingdao Mytilus galloprovincialis were observed within and between individuals. The maximum growth direction of the aragonite in Modiolus elongatus is higher than that of the vertical direction, and no obvious differences between individuals were displayed. The crystallinity of Modiolus kurilensis is higher than that of above mentioned two types of mussels in Qingdao-offshore, and the aragonite crystallinity of the maximum growth direction is higher than that of the vertical direction. Different crystallinity in different growth directions may result from the strict control of shell mineralization by biological macromolecules.

(2) The minerals of Bathymodiolus platifrons in the cold seep in the Fomosa Ridge (Site F) are aragonite and calcite. The mineral in the prism layer of Bathymodiolus platifrons is calcite, and the nacre layer is aragonite. The Raman shifts of the two minerals are not different from those of mussels in offshore environment. There is no obvious difference in the FWHM of the main peak of calcium carbonate between Bathymodiolus platifrons and Modiolus elongatus, Mytilus galloprovincialis. The crystallinity of the maximum growth direction is higher than that of the vertical direction. Bathymodiolus platifrons adapt to the cold seep environment. In the areas with high methane concentrations, the growth rate is comparable with that in the offshore areas. No obvious differences in mineralization were observed.

(3) The hydrothermal environment has a significant influence on the minerals of Bathymodiolus manusensis. The mineral in the prism layer of Bathymodiolus manusensis in DESMOS hydrothermal is calcite, and the nacre layer is aragonite. The FWHM of nacre layer in the mussel shells is larger than that in other environments. And there are significant differences among individuals. The crystallinity of aragonite is poor, and the mineralization of shells is closely related to the complexity of hydrothermal environment. The temperature gradient of hydrothermal field is large. Various kinds and different concentrations of heavy metal ions affect the survival of the mussels.