Exploring the hidden shallows: inner-shelf reef growth and future trajectories of reef geomorphic change

在一系列与环境和气候变化相关的干扰下，区域范围内珊瑚覆盖和珊瑚礁结构复杂性的恶化已经被记录下来，全球珊瑚礁生态系统的变化规模如此之大，以至于许多人认为珊瑚礁增生的停止是最终和迫在眉睫的轨迹。因此，珊瑚礁科学中最紧迫和最根本的挑战之一是在迅速变化的气候和环境条件下预测珊瑚礁的未来。响应可能会因区域和珊瑚礁而异，但最终将由两组基本因素决定：1)珊瑚礁上主要碳酸盐产生者和侵蚀者的生态（以及对环境变化的生态响应），因为它们相互作用决定了珊瑚礁是否有可能在其结构中添加新的碳酸盐；2)该珊瑚礁的地貌演化状态和未来生长潜力作为其过去相对于海平面的生长历史的函数。虽然关于本地和区域空间尺度当代生态过程的大量数据可以为这场辩论提供信息，但关于这些当代过程所依赖的珊瑚礁结构的年龄、生长历史和形态发生进化状态的数据却非常缺乏。事实上，对文献的回顾表明，关于全新世珊瑚礁增生率的数据（作为随时间的净垂直珊瑚礁生长的衡量标准）存在于世界珊瑚礁的1%以下。这是任何预测未来珊瑚礁生长速率（以及地貌变化）的尝试的主要限制，并且固有地抑制了将过去珊瑚礁生长速率和时间尺度（在单个珊瑚礁尺度上）的数据整合到未来生态状态评估中，从而纳入管理决策。例如，如果一个珊瑚礁在过去的100年到1000年里一直在海平面上，并且处于一个基本上衰老的进化状态（“衰老”状态：sensu Hopley 1982），那么不仅它目前的栖息地多样性受到限制，而且它的直接生长潜力和未来持续增长的潜力也会受到严重损害。其含义是明确的- -最明智的管理计划不仅应综合有关当代珊瑚礁生态和生境类型的知识，而且还应作为未来潜在地貌表现的预测者，了解过去和潜在的珊瑚礁增长率以及珊瑚礁目前的地貌演化状态。为了解决这个问题，我们需要包容性的数据集来帮助我们了解：1)各个地区的不同珊瑚礁何时开始生长；2)它们在不同环境下的增长速度；3)哪些珊瑚礁在最近的过去是最活跃的；4)哪些珊瑚礁，作为其当前地貌状态的函数，在未来有进一步增加的最大潜力。因此，该项目的主要目标是解决未来珊瑚礁轨迹挑战的一部分-过去地貌表现和当前珊瑚礁进化状态的相关性和作用，作为未来珊瑚礁增生潜力的预测器。这具有直接的长期管理意义，因为当代珊瑚礁形态是影响未来形态的关键因素之一，从而影响珊瑚礁生境的特征和多样性。具体来说，该项目将开发新的、具有空间包容性的珊瑚礁增生和进化状态数据集——以澳大利亚大堡礁内大陆架区域为例。虽然以区域为重点，但由于了解珊瑚礁生长历史，当代生态状态和未来栖息地复杂性之间的联系，这项工作具有全球范围的相关性。

Regional-scale deteriorations in coral cover and reef architectural complexity, driven by a suite of environmental and climate-change related disturbances, have been documented, with the scale of global reef ecosystem change such that a cessation of reef accretion has been argued by many as the ultimate and imminent trajectory. One of the most pressing and fundamental challenges in coral reef science is thus to project the future for coral reefs under rapidly changing climatic and environmental conditions. Responses will likely vary region by region, and reef by reef, but will ultimately be determined by two basic sets of factors: 1) the ecology (and ecological responses to environmental change) of the key carbonate producers and eroders on a reef, because these interact to determine whether a reef has the potential to add new carbonate to its structure; and 2) the geomorphic evolutionary state and future growth potential of that reef as a function of its past growth history relative to sea level. Whilst there is an expansive and rapidly growing body of data on local and regional spatial scale contemporary ecological processes to inform this debate, there is a remarkable paucity of data on the age, growth history and morphogenetic evolutionary state of the reef structures on which these contemporary processes operate. Indeed, a review of the literature suggests that data on Holocene coral reef accretion rates (as a measure of net vertical reef growth over time) exists for something well below 1% of the World's coral reefs. This represents a major limitation in any attempts to project future rates of reef growth (and thus geomorphic change), and inherently inhibits attempts to integrate data on past rates and timescales of reef growth (at the individual reef scale) into assessments of future ecological states, and thus into management decision-making. For example, if a reef has been at sea level for the past several 100's to 1000's of years, and exists in an essentially senescent evolutionary state (a 'senile' state: sensu Hopley 1982), not only will its current habitat diversity be restricted but its immediate growth potential and its potential for sustained future growth will be severely impaired. The implications of this are clear - that the best informed management plans should integrate knowledge not only of contemporary reef ecology and habitat types but also, as a predictor of future potential geomorphic performance, an understanding of past and potential reef growth rates and of the current geomorphic evolutionary state of a reef. To address this issue, inclusive datasets are needed that can inform our understanding of: 1) when different reefs within individual regions started to grow; 2) how fast they accreted in different settings; 3) which reefs have been most actively accreting in the very recent past; and 4) which reefs, as a function of their current geomorphic state, have the greatest potential for further accretion in the future. The primary goal of this project is thus to address one part of the future reef trajectory challenge - the relevance and role of past geomorphic performance and of current reef evolutionary state as a predictor of future reef accretion potential. This has direct long-term management relevance because contemporary reef morphology is one of the key contributing factors that influences future morphology and thus the characteristics and diversity of reef habitats. Specifically, the project will develop new, spatially inclusive reef accretion and evolutionary state datasets - taking as a case site the inner-shelf regions of Australia's Great Barrier Reef. Whilst regionally focused, the work has global scale relevance because of the implications for understanding the links between reef growth histories, contemporary ecological states and future habitat complexity.