MCR LTER: Coral Reef: Priority effects in coral-macroalgae interactions can drive alternate community paths in the absence of top-down control, data for Adam 2022 Ecology

These data were generated in support of the manuscript: Adam TC, Holbrook SJ, Burkepile DE, Speare KE, Brooks AJ, Ladd MC, Shantz AA, Thurber RLV, and Schmitt RJ, Ecology The outcomes of species interactions can vary greatly in time and space with the outcomes of some interactions determined by priority effects. On coral reefs, benthic algae rapidly colonize the disturbed substrate. In the absence of top-down control from herbivorous fishes, these algae can inhibit the recruitment of reef-building corals, leading to a persistent phase shift to a macroalgae-dominated state. Yet, corals may also inhibit colonization by macroalgae, and thus the effects of herbivores on algal communities may be strongest following disturbances that reduce coral cover. Here, we report results from experiments conducted on the fore reef of Moorea, French Polynesia, where we: 1) tested the ability of macroalgae to invade coral-dominated and coral-depauperate communities under different levels of herbivory, 2) explored the ability of juvenile corals (Pocillopora spp.) to suppress macroalgae, and 3) quantified the direct and indirect effects of fish herbivores and corallivores on juvenile corals. We found that macroalgae proliferated when herbivory was low but only in recently disturbed communities where coral cover was also low. When coral cover was < 10%, macroalgae increased 20-fold within one year under reduced herbivory conditions relative to high herbivory controls. Yet, when coral cover was high (50%), macroalgae were suppressed irrespective of the level of herbivory despite ample space for algal colonization. Once established in communities with low herbivory and low coral cover, macroalgae suppressed recruitment of coral larvae, reducing the capacity for coral replenishment. However, when we experimentally established small juvenile corals (2 cm diameter) following a disturbance, juvenile corals inhibited macroalgae from invading local neighborhoods, even in the absence of herbivores, indicating a strong priority effect in macroalgae coral interactions. Surprisingly, fishes that initially facilitated coral recruitment by controlling algae had a net negative effect on juvenile corals via predation. Corallivores reduced growth rates of corals exposed to fishes by ~ 30% relative to fish exclosures despite increased competition with macroalgae within the exclosures. These results highlight that different processes are important for structuring coral reef ecosystems at different successional stages and underscore the need to consider multiple ecological processes and historical contingencies to predict coral community dynamics. This material is based upon work supported by the U.S. National Science Foundation under Grant No. OCE 16-37396 (and earlier awards) as well as a generous gift from the Gordon and Betty Moore Foundation. Research was completed under permits issued by the French Polynesian Government (Délégation à la Recherche) and the Haut-commissariat de la République en Polynésie Francaise (DTRT) (Protocole d'Accueil 2005-2022). This work represents a contribution of the Moorea Coral Reef (MCR) LTER Site.

本数据集为支撑下述论文而生成：Adam TC、Holbrook SJ、Burkepile DE、Speare KE、Brooks AJ、Ladd MC、Shantz AA、Thurber RLV与Schmitt RJ发表于《生态学（Ecology）》的研究。物种互作的结果随时间与空间存在显著差异，部分互作的结果由优先效应（priority effects）决定。在珊瑚礁生态系统中，底栖藻类（benthic algae）会快速定植于受扰动的基质之上。若无植食性鱼类的下行控制（top-down control），这类藻类会抑制造礁珊瑚（reef-building corals）的定植，最终导致生态系统持续向大型藻类主导的（macroalgae-dominated）状态发生相变。但珊瑚同样可以抑制大型藻类的定植，因此在降低珊瑚覆盖度的扰动事件发生后，植食动物对藻类群落的调控作用可能最为显著。本研究报告了在法属波利尼西亚茉莉雅岛（Moorea）礁前带（fore reef）开展的实验结果，实验内容包括：1）测试不同植食压力水平下，大型藻类入侵珊瑚主导与珊瑚缺失群落的能力；2）探究幼龄珊瑚（juvenile corals，杯形珊瑚属Pocillopora spp.）抑制大型藻类的能力；3）量化植食性鱼类与食珊瑚动物（corallivores）对幼龄珊瑚的直接与间接影响。研究发现，仅在近期受扰动且珊瑚覆盖度较低的群落中，低植食压力下大型藻类会大量增殖。当珊瑚覆盖度低于10%时，相较于高植食压力对照组，低植食压力组的大型藻类在一年内生物量增长可达20倍。但当珊瑚覆盖度较高（50%）时，无论植食压力水平如何，大型藻类的生长均受到抑制，即便藻类定植有充足的空间。一旦在低植食压力、低珊瑚覆盖度的群落中定植，大型藻类会抑制珊瑚幼虫的定植，降低珊瑚种群的补充能力。然而，当我们在扰动后通过实验定植小型幼龄珊瑚（直径2 cm）时，即便无植食动物存在，幼龄珊瑚仍可抑制大型藻类入侵其周边区域，这表明大型藻类与珊瑚的互作存在显著的优先效应。令人意外的是，最初通过调控藻类促进珊瑚定植的鱼类，却会通过捕食作用对幼龄珊瑚产生净负面效应。与鱼类排除组相比，暴露于鱼类环境中的珊瑚，其生长速率会降低约30%——尽管排除组内珊瑚与大型藻类的竞争压力更高。本研究结果表明，在珊瑚礁生态系统的不同演替阶段，塑造群落结构的关键生态过程存在差异；同时也强调，若要预测珊瑚群落动态，需综合考量多种生态过程与历史偶然性事件。本研究工作得到美国国家科学基金会（Grant No. OCE 16-37396及此前的资助项目）以及戈登与贝蒂·摩尔基金会的慷慨资助。本研究的开展获得了法属波利尼西亚政府（Délégation à la Recherche）与法国驻波利尼西亚高级专员公署（DTRT，Protocole d'Accueil 2005-2022）签发的许可。本成果为茉莉雅珊瑚礁（Moorea Coral Reef, MCR）长期生态研究（Long-Term Ecological Research, LTER）站点的贡献内容。