Rice University, BioSciences at Rice, Houston, Texas, United States of America.
Oregon State University, Department of Microbiology, Corvallis, Oregon, United States of America.
PLoS One. 2018 Jun 20;13(6):e0199462. doi: 10.1371/journal.pone.0199462. eCollection 2018.
Bioerosion, the removal of calcium carbonate from coral frameworks by living organisms, influences a variety of reef features, from their topographic complexity to the net balance of carbonate budgets. Little is known, however, about how macroborers, which bore into reef substrates leaving traces greater than 0.1 mm diameter, are distributed across coral reefs, particularly reef systems with high (>50%) stony coral cover or at mesophotic depths (≥30 m). Here, we present an accurate and efficient method for quantifying macroborer densities from stony coral hosts via image analysis, using the bioeroding barnacle, Lithotrya dorsalis, and its host coral, Orbicella franksi, as a case study. We found that in 2014, L. dorsalis densities varied consistently with depth and host percent cover in two Atlantic reef systems: the Flower Garden Banks (FGB, northwest Gulf of Mexico) and the U.S. Virgin Islands (USVI). Although average barnacle density was nearly 4.5 times greater overall in the FGB than in the USVI, barnacle density decreased with depth in both reef regions. Barnacle density also scaled negatively with increasing coral cover in the study areas, suggesting that barnacle populations are not strictly space-limited in their distribution and settlement opportunities. Our findings suggest that depth and host coral cover, and potentially, local factors may strongly influence the abundance of macroborers, and thus the rate of CaCO3 loss, in a given reef system. Our image analysis method for quantifying macroborers can be standardized across historical and modern reef records to better understand how borers impact host growth and reef health.
生物侵蚀，即生物从珊瑚框架中去除碳酸钙，会影响到各种珊瑚礁特征，从地形复杂性到碳酸盐预算的净平衡。然而，人们对大型穿孔生物（在珊瑚礁基质上钻孔留下直径大于 0.1 毫米的痕迹）在珊瑚礁中的分布情况知之甚少，特别是在高（>50%）石珊瑚覆盖率或中光层（≥30 米）的珊瑚礁系统中。在这里，我们提出了一种通过图像分析从石珊瑚宿主中准确、高效地量化大型穿孔生物密度的方法，以生物侵蚀藤壶 Lithotrya dorsalis 和其宿主珊瑚 Orbicella franksi 为例。我们发现，在 2014 年，L. dorsalis 的密度在两个大西洋珊瑚礁系统（墨西哥湾西北部的花园银行群岛和美属维尔京群岛）中与深度和宿主百分比覆盖度呈一致变化。尽管藤壶的平均密度在花园银行群岛比美属维尔京群岛总体上高出近 4.5 倍，但在这两个珊瑚礁区域，藤壶密度都随深度的增加而降低。藤壶密度也与研究区域中珊瑚覆盖度呈负相关，这表明藤壶种群在其分布和定居机会方面并不严格受到空间限制。我们的研究结果表明，深度和宿主珊瑚覆盖率，以及潜在的局部因素可能会强烈影响大型穿孔生物的丰度，从而影响给定珊瑚礁系统中 CaCO3 的损失速度。我们用于量化大型穿孔生物的图像分析方法可以在历史和现代珊瑚礁记录中标准化，以更好地了解穿孔生物如何影响宿主的生长和珊瑚礁的健康。
