RAPID: Resilience of Caribbean octocorals following Hurricanes Irma and Maria

干扰和随后的恢复是珊瑚礁种群动态的关键因素，但在加勒比地区，硬珊瑚的丰度一直在稳步下降，同时藻类的丰度增加。这种描述忽略了一个观察结果，即在一些有定量数据的地点，八爪珊瑚（海扇和海羽）的丰度有所增加。对这些数据的仔细检查表明，八爪珊瑚有时也在减少，但与硬珊瑚不同的是，它们恢复了，现在至少在一些地方比30年前更加丰富。这些生物丰度的变化似乎是由于八爪珊瑚具有更大的恢复力。飓风“厄玛”和“玛丽亚”对美国维尔京州圣约翰南岸造成的破坏。提供了解这些流程的窗口。在过去的30年里，我们一直在监测这些珊瑚礁上的硬珊瑚的丰度，而在过去的4年里，我们一直在跟踪观察八角珊瑚。将研究新开辟的珊瑚礁空间的殖民化，以确定是否可以预期丰度的进一步变化，并了解八珊瑚种群更大的恢复能力的基础。描述八爪珊瑚相对于硬珊瑚的恢复能力，将对加勒比珊瑚礁在一个压力水平日益增加的世界中的命运产生影响。这对决策者和管理者来说很重要，因为硬珊瑚和八角珊瑚提供的生态系统服务有很大的不同。除了对我们对珊瑚礁过程的基本理解产生影响外，这笔拨款还将支持研究生的培训。50多年来，人们一直认为珊瑚礁是扰动驱动的系统，扰动对维持珊瑚礁群落的多样性起着重要作用。然而，过去30年的特点是硬化菌的丰度下降，通常与飓风和漂白事件等急性事件有关。了解在这些事件中发生的干扰和随后的恢复的影响对于理解过去30年来发生的珊瑚礁结构变化至关重要。在有数据的地点，石珊瑚和八珊瑚相对丰度的变化似乎与干扰相一致，随后是十珊瑚恢复和缺乏石珊瑚恢复。这种变化必须反映出幼虫供应、定居和/或存活的变化，而这些差异在干扰后应该是最大的。飓风厄玛和玛丽亚对圣约翰南岸的影响提供了一个机会来描述扰动后的补充，并确定可能限制当代珊瑚礁成功补充的过程。在过去的4年里，已经有了关于八珊瑚和硬珊瑚种类丰度的数据，每年的普查提供了关于八珊瑚的补充和生存以及八珊瑚丰度的物种水平特征的数据。在毫米和厘米的尺度上，栖息地的补充和生存也与空间复杂性有关，对飓风驱动的空间复杂性变化的影响也将进行评估。干扰的频率和强度至少将维持在历史水平或更高的水平。对扰动前后的数据进行比较，将有力地评估八珊瑚和硬珊瑚的恢复能力，以及招募和招募生存在其相对恢复能力中的作用。因此，飓风厄玛和玛丽亚的影响为未来珊瑚礁的性质提供了一个窗口。

Disturbance and subsequent recovery have been key factors in the dynamics of coral reef populations, but in the Caribbean, there has been a steady decline in the abundance of hard corals accompanied by increased abundance of algae. This characterization overlooks the observation that at some sites for which there are quantitative data, the abundances of octocorals (sea fans and sea plumes) have increased. Closer inspection of those data reveals that octocorals have also declined at times, but unlike hard corals, they recovered and are now more abundant in at least some locations than 30 years ago. The change in abundances of these organisms would appear to due to the greater resilience of octocorals. The damage inflicted by Hurricanes Irma and Maria on the south shore of St. John, U.S. Virgin Is. provides a window into these processes. Abundances of hard corals on these reefs have been monitored for the past 30 years and the octocorals have been followed for the past 4 years. Colonization of the newly opened space on the reef will be studied to determine if further shifts in abundances can be expected and to understand the basis for the greater resilience of octocoral populations. Characterizing the resilience of octocorals relative to hard corals will have implications for the fate of Caribbean reefs in a world subject of increasing levels of stress. This will be of importance to policy makers and managers, because hard corals and octocorals provide substantially different ecosystem services. In addition to its impact on our fundamental understanding of reef processes, the grant will support the training of graduate students.Coral reefs have been recognized to be disturbance driven systems for over 50 years and disturbance has been considered to be important in maintaining diversity of reef communities. However, the past 30 years has been characterized by declines in the abundances of scleractinians, often associated with acute events such as hurricanes and bleaching events. A knowledge of the effects of disturbance and subsequent recovery that occurs during these events is critical to understanding the changes in reef structure that have occurred in the last 30 years. At sites for which there are data, changes in the relative abundance of scleractinians and octocorals appear to coincide with disturbance followed by octocoral recovery and a lack of scleractinian recovery. This change must reflect changes in larval supply, settlement, and/or survival, and those differences should be greatest following disturbance. The effects of Hurricanes Irma and Maria on the south shore of St. John provide the opportunity to characterize recruitment following disturbance and identify the processes that may limit successful recruitment on contemporary reefs. Data are already available on the abundance of octocoral and scleractinian species over the past 4 years, and annual censuses have provided data on octocoral recruitment and survival and species level characterizations of octocoral abundances. Recruitment and survival are also being related to spatial complexity of the habitat at the scale of mm and cm and the effects on hurricane driven changes in that spatial complexity will also be assessed. The frequency and intensity of disturbances will at the least continue at historical or greater levels. The comparison of data from before and now after disturbance will provide a powerful assessment of the resilience of octocorals and scleractinians and the role of recruitment and recruit survival in their relative resilience. Thus the effects of Hurricanes Irma and Maria provide a window on the nature of future reefs.