RAPID: Here we go again - The fate of Diadema antillarum and Caribbean reefs in the 21st century

珊瑚礁底栖生物群落的组合和功能在一定程度上受到以藻类为食的食草动物的控制，藻类与包括珊瑚和海绵物种在内的各种分类群竞争空间。据推测，在加勒比地区，黑海胆（Diadema antillarum）是一种重要的食草动物，它将大型藻类的种类组成和生物量控制在较低水平，并促进造礁珊瑚的补充和生存，从而导致珊瑚礁以珊瑚为主的状态。最近的海胆死亡为了解这种食草动物自上而下的控制作用提供了自然清除实验条件，特别是通过量化底栖动物功能群在海胆丰度上的空间排列进展。本研究评估了这一关键物种的消失对珊瑚礁群落结构和功能的影响，利用创新的成像工具量化了加勒比地区Diadema灭绝初期，波多黎各Culebra珊瑚礁上的D. antillarum、优势珊瑚物种（Porites）、草地藻类和大型藻类的群落结构、大小分布和空间分散的精细变化。整个加勒比地区的D. antillarum的死亡凸显了了解食草动物如何以及何时在塑造珊瑚礁群落中发挥作用的重要性。该RAPID奖正在创建一个丰富的数字数据集，将用于评估多种生态问题，并为本科生和研究生的研究提供大量机会。这一关键物种的消失预计将影响整个珊瑚礁群落的结构和功能，以及珊瑚草坪藻和大型藻的丰度和分布。该项目使用创新的空间明确工具，量化了加勒比地区Diadema灭绝初期，波多黎各库莱布拉珊瑚礁上的D. antillarum、Porites astreoides（优势珊瑚物种）、草地藻类和大型藻类（Dictyota spp.）的群落结构、大小分布和空间分散的精细时空变化。基于自上而下的控制、竞争和渗透理论，研究人员假设（H1） D. antillarum与珊瑚礁的群落结构之间存在很强的关系；（H2）大型藻类/草皮藻类覆盖的增加始于藻团的不均匀分散，随后藻团在珊瑚礁和P. asteroides菌落周围聚集，这将导致（H3） P. asteroides的人口统计学参数（如生长、大小-结构、分布和分布）的减少。由于窒息，遮阳和与藻类的相互作用而导致的招募。他们假设（H4）珊瑚礁的营养动态将发生变化，特别是由于基础资源的多样化和消费者营养生态位的扩大。调查人员正在使用动态结构软件来创建大面积的图像，再现珊瑚礁区域的数字重建。他们利用了cullebra（波多黎各）现有项目的数据，该项目自2020年以来收集了90多张高分辨率（厘米尺度）、大面积图像（LAIs， 100平方米）。他们正在生成双月lai（8个时间点），以评估作为灭绝函数的精细和快速反应。正在收集不同基础资源和营养行业/水平的样本，进行稳定同位素分析和贝叶斯混合模型，以量化由于珊瑚礁群落对海胆死亡的反应而导致的营养动力学变化。这些研究活动遵循基于前后实验方法和高分辨率时间趋势的分析框架。正在将不同的统计建模技术纳入这一框架，以处理项目的假设和协同活动。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Coral reef benthic community assemblage and functioning are controlled in part by herbivores that graze on algae, which compete for space with various taxa, including coral and sponge species. In the Caribbean, it is hypothesized that the black sea urchin, Diadema antillarum, is a keystone grazer that controls macroalgae species composition and biomass at low levels and facilitates the recruitment and survival of reef-building corals, leading to a coral-dominated state of reefs. The recent D. antillarum die-off provides the conditions of a natural removal experiment useful to understand the top-down control exertion of this herbivore, especially by quantifying the spatial arrangement progression of benthic functional groups across urchin abundances. This study is assessing the impact of the loss of this keystone species on reef community structure and function using innovative imaging tools to quantify the fine-scale changes in the community structure, the size distribution, and spatial dispersion of D. antillarum, the dominant coral species (Porites), and turf-algae and macroalgae on the reefs of Culebra, Puerto Rico, during the initial phase of the Diadema die-off in the Caribbean. The Caribbean-wide D. antillarum die-off highlights the importance of understanding how and when herbivores play a role in shaping reef communities. This RAPID award is creating a rich digital dataset that will be leveraged to assess multiple ecological questions and provide numerous opportunities for undergraduate and graduate research studies.The loss of this keystone species is expected to impact overall reef community structure and function and the abundance and distribution of coral turf-algae and macroalgae. The project uses innovative spatially explicit tools to quantify the fine-scale spatiotemporal changes in the community structure, size distribution, and spatial dispersion of D. antillarum, Porites astreoides (dominant coral species), and turf-algae and macroalgae (Dictyota spp.) on the reefs of Culebra, Puerto Rico, during the initial phase of the Diadema die-off in the Caribbean. Based on top-down control, competition, and percolation theory, the investigators hypothesize (H1) a strong relationship between D. antillarum and the community structure of reefs, (H2) an increase in macroalgae/turf algae cover starting with a non-uniform dispersion of algae clumps, followed by the coalescing of algae clumps percolated across the reefs and around P. asteroides colonies, which will result in (H3) a decrease of P. asteroides demographic parameters (e.g., growth, size-structure, recruitment) due to smothering, shading, and interactive effects with algae. They hypothesize (H4) that the trophic dynamics of reefs will shift, especially by the diversification of basal resources and expansion of trophic niches of consumers. The investigators are using Structure-from-Motion software to create large-area images that reproduce a digital reconstruction of reef plots. They leverage data from an existing project in Culebra (Puerto Rico) that has collected over 90 high resolution (cm-scale), large-area images (LAIs, 100 m2) since 2020. They are generating bi-monthly LAIs (8 time points) to assess the fine-scale and fast responses as a function of the die-off. Samples across different basal resources and trophic guilds/levels are being collected to perform stable isotope analysis and Bayesian mixing models to quantify shifts in trophic dynamics due to the response of the reef community to the urchin die-off. These research activities follow an analytical framework based on a before-and-after experimental approach and high-resolution temporal trends. Different statistical modeling techniques are being incorporated in this framework to address the projects' hypotheses and synergistic activities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.