In an era of global change, the fate and form of reef habitats will depend on shifting assemblages of organisms and their responses to multiple stressors. Multiphyletic assemblages of calcifying and bioeroding species contribute to a dynamic balance between constructive and erosive processes, and reef-framework growth occurs only when calcium-carbonate deposition exceeds erosion. Each contributing species exhibits a unique combination of environmental sensitivities, trophic needs, and competitive abilities, making the net outcome of their habitat-altering behavior difficult to predict. In this study, standardized blocks of clean, massive Porites were placed at six reef sites in the eastern tropical Pacific, in the strongly and more-weakly upwelling Gulfs of Panamá (GoP) and Chiriquí (GoC), respectively. Sites were chosen to characterize the unique thermal and carbonate-chemistry conditions of each gulf. Satellite products were used to examine differences in sea-surface productivity, and surveys were conducted to quantify the abundance of important grazing taxa. After two years in situ, the Porites blocks were collected and scanned using high-resolution computed tomography to volumetrically quantify both endolithic and epilithic habitat alteration. Scan-volumes were further classified into functional groups according to morphology to quantify external bioerosion by fish and sea urchins, as well as the calcifying and bioeroding activity of crustose coralline algae, scleractinian corals, mollusks, annelids, and barnacles. The GoP, which has higher productivity, cooler temperatures, and periodically lower pH conditions, had higher rates of macroboring, but also higher rates of calcification. These unexpectedly higher rates of calcification in the GoP were a result of high recruitment of suspension-feeding taxa, particularly barnacles and vermiform fauna that have poor reef-forming potential. External bioerosion by grazers was the dominant process influencing these dead coral substrates across both gulfs, contributing to higher rates of net erosion in the GoC and underscoring the important roles that urchins and fish play in not just removing algae on reefs, but also eroding reef habitat. Ultimately these findings reveal that the trophic requirements of habitat-altering taxa are closely tied to reef-framework stability, and that environmental conditions conducive to carbonate precipitation are not necessarily those that will lead to habitat persistence.

中文翻译：

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东热带太平洋珊瑚礁框架的上升流和持久性

在全球变化的时代，珊瑚礁栖息地的命运和形式将取决于生物群落的变化及其对多种压力的反应。钙化和生物侵蚀物种的多系组合有助于建设性和侵蚀性过程之间的动态平衡，只有当碳酸钙沉积超过侵蚀时，珊瑚礁框架才会生长。每个贡献物种都表现出环境敏感性、营养需求和竞争能力的独特组合，这使得它们改变栖息地行为的最终结果难以预测。在这项研究中，标准化的干净、巨大的Porites块被放置在热带太平洋东部的六个珊瑚礁地点，分别位于巴拿马湾（GoP）和奇里基湾（GoC）的强烈和较弱的上升流中。选择地点来表征每个海湾独特的热和碳酸盐化学条件。卫星产品用于检查海面生产力的差异，并进行调查以量化重要放牧类群的丰度。在原位两年后，Porites使用高分辨率计算机断层扫描收集和扫描块，以体积量化内石和石上栖息地的改变。扫描体积根据形态进一步分为功能组，以量化鱼类和海胆的外部生物侵蚀，以及硬壳珊瑚藻、石珊瑚、软体动物、环节动物和藤壶的钙化和生物侵蚀活动。GoP 具有较高的生产率、较低的温度和周期性较低的 pH 条件，具有较高的大孔率，但也有较高的钙化率。GoP 中这些出乎意料的较高钙化率是悬浮摄食类群大量补充的结果，特别是具有较差成礁潜力的藤壶和蠕虫动物群。食草动物的外部生物侵蚀是影响这两个海湾这些死珊瑚基质的主要过程，导致 GoC 净侵蚀率更高，并强调了海胆和鱼类不仅在去除珊瑚礁上的藻类，而且在侵蚀珊瑚礁栖息地方面发挥的重要作用. 最终，这些发现表明，改变栖息地的分类群的营养需求与珊瑚礁框架的稳定性密切相关，有利于碳酸盐沉淀的环境条件不一定会导致栖息地持续存在。