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有关的扰动的推动下，珊瑚礁覆盖率和珊瑚礁结构的复杂性在区域范围内恶化，这是有据可查的，全球珊瑚礁生态系统变化的规模如此之大，许多人认为停止珊瑚礁的生长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。这些反应可能会因区域和礁石的不同而有所不同，但最终将由两组基本因素决定：1)珊瑚礁上主要碳酸盐生产者和碳酸盐生物的生态(和对环境变化的生态反应)，因为这些相互作用决定了珊瑚礁是否有可能在其结构中增加新的碳酸盐；2)珊瑚礁的地貌演变状态和未来增长潜力是其过去相对于海平面的生长历史的函数。虽然有大量关于当地和区域空间尺度的当代生态过程的数据为这场辩论提供了信息，但关于这些当代过程所作用的珊瑚礁结构的年龄、生长史和形态形成演化状态的数据明显缺乏。事实上，对文献的回顾表明，关于全新世珊瑚礁增加率的数据(作为衡量珊瑚礁随时间净增长的指标)存在于远低于1%的世界珊瑚礁。这是对预测未来珊瑚礁增长速度(从而影响地貌变化)的任何尝试的主要限制，并固有地阻碍了将过去珊瑚礁增长速度和时间尺度的数据纳入对未来生态状态的评估，从而纳入管理决策的尝试。例如，如果一个珊瑚礁在过去100‘S到1000年S的时间里一直在海平面上，并且基本上处于一种衰老的进化状态(一种’衰老‘状态：Sensu Hopley 1982)，不仅它目前的栖息地多样性将受到限制，而且它的直接增长潜力和未来持续增长的潜力将受到严重损害。这一点的影响是明确的--最明智的管理计划不仅应纳入关于当代珊瑚礁生态和生境类型的知识，而且应作为未来潜在地貌表现的预测指标，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变状态。为了解决这一问题，需要包容性的数据集，以帮助我们了解：1)个别区域内的不同珊瑚礁何时开始生长；2)它们在不同的环境中生长的速度有多快；3)哪些珊瑚礁在最近的过去一直是最活跃的；以及4)哪些珊瑚礁根据其当前的地貌状态，未来最有可能进一步生长。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--过去的地貌表现和当前的珊瑚礁演化状态作为未来珊瑚礁增长潜力的预测指标的相关性和作用。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。具体地说，该项目将开发新的、空间上包含的珊瑚礁吸积和演化状态数据集--以澳大利亚大堡礁内陆架区域为例。虽然这项工作着眼于区域，但具有全球范围的相关性，因为它意味着理解珊瑚礁生长历史、当代生态状况和未来栖息地复杂性之间的联系。

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.