Quantifying Attributes of Boring Bivalve Populations in Corals Using Micro-Computed Tomography

Bioerosion plays a crucial factor in shaping the structure and function of coral reef ecosystems, with bioeroders actively altering both the physical and ecological dynamics of coral substrates.Despite their importance, studying internal bioeroders in corals presents significant challenges owing to their cryptic nature within the skeletal structures. Additionally, invasive methods are often required to reveal the subtle and microscopic bioerosive alterations they induce in calcium carbonate substrates. Here, we demonstrate the effectiveness of high-resolution micro-computed tomography (μCT) in quantifying the abundance, size, distribution, and growth directions of coral bioeroders such as cryptic calcareous bivalves in the northern Red Sea. We scanned three coral species inhabited with by bioeroders, followed by the utilization of three-dimensional image analysis software to identify, count, and measure each bivalve within the coral skeleton, along with quantifying boring cavity volumes. We revealed that μCT captures small boring cavities (< 1mm), providing more accurate abundance estimates of live and dead boring bivalves than the skeleton decalcification technique, with the added benefits of being rapid and non-destructive in contrast to traditional methods. Furthermore, measurements of empty cavity volumes enabled the estimations of the contribution of bioeroders to the overall coral skeletal porosity. Overall, our study highlights μCT as a practical and effective tool for studying cryptic coral bioeroders, providing novel ecological insights into bioeroder population ecology and coral-bioeroder interactions.

生物侵蚀（Bioerosion）在塑造珊瑚礁生态系统的结构与功能中发挥着关键作用，生物侵蚀者（bioeroders）会主动改变珊瑚基质的物理与生态动态。尽管其重要性不言而喻，但对珊瑚体内的生物侵蚀者开展研究却面临显著挑战——这源于它们隐匿于珊瑚骨骼结构中的特性。此外，要观测它们在碳酸钙基质中诱发的细微微观侵蚀改变，往往需要采用侵入性实验方法。本研究证实了高分辨率微计算机断层扫描（micro-computed tomography，μCT）在量化红海北部珊瑚生物侵蚀者（如隐匿性钙化双壳类）的丰度、体型、分布及生长方向方面的有效性。我们对三种被生物侵蚀者定植的珊瑚物种进行了扫描，随后借助三维图像分析软件识别、计数并测量珊瑚骨骼内的每一只双壳类，同时量化了钻洞空腔的体积。研究表明，μCT可捕捉到尺寸小于1毫米的小型钻洞空腔，相较于骨骼脱钙技术（skeleton decalcification technique），其对活体与死亡钻洞双壳类的丰度估算更为精准，且相比传统方法还具备快速、无损的额外优势。此外，通过对空腔体积的测量，可估算出生物侵蚀者对珊瑚整体骨骼孔隙率的贡献程度。总体而言，本研究凸显了μCT作为研究隐匿性珊瑚生物侵蚀者的实用高效工具的价值，为生物侵蚀者种群生态学以及珊瑚-生物侵蚀者互作关系提供了全新的生态学认知。