ARC Centre of Excellence for Coral Reef Studies and College of Science and Engineering, James Cook University, Townsville, Queensland 4811, Australia.
Function, Evolution and Anatomy Research Lab and Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia; Australian Museum Research Institute, Australian Museum, Sydney, New South Wales 2010, Australia.
Sci Total Environ. 2020 Sep 10;734:139422. doi: 10.1016/j.scitotenv.2020.139422. Epub 2020 May 24.
The presence of key organisms is frequently associated with the delivery of specific ecosystem functions. Areas with such organisms are therefore often considered to have greater levels of these functions. While this assumption has been the backbone of coral reef ecosystem-based management approaches for decades, we currently have only a limited understanding of how fish presence equates to function on coral reefs and whether this relationship is susceptible to stressors. To assess the capacity of a stressor to shape function delivery we used a multi-scale approach ranging from tens of kilometres across the continental shelf of Australia's Great Barrier Reef, down to centimetres within a reef habitat. At each scale, we quantified the spatial extent of a model function (detritivory) by a coral reef surgeonfish (Ctenochaetus striatus) and its potential to be shaped by sediments. At broad spatial scales, C. striatus presence was correlated strongly with algal turf sediment loads, while at smaller spatial scales, function delivery appears to be constrained by algal turf sediment distributions. In all cases, sediment loads above ~250-500 g m were associated with a marked decrease in fish abundance or feeding activity, suggesting that a common ecological threshold lies within this range. Our results reveal a complex functional dynamic between proximate agents of function delivery (fish) and the ultimate drivers of function delivery (sediments), which emphasizes: a) weaknesses in the assumed links between fish presence and function, and b) the multi-scale capacity of algal turf sediments to shape reef processes. Unless direct extractive activities (e.g. fishing) are the main driver of function loss on coral reefs, managing to conserve fish abundance is unlikely to yield the desired outcomes. It only addresses one potential driver. Instead, management of both the agents that deliver functions (e.g. fishes), and the drivers that modify functions (e.g. sediments), is needed.
关键生物的存在通常与特定生态系统功能的提供有关。因此，拥有这些生物的区域通常被认为具有更高水平的这些功能。尽管这一假设几十年来一直是珊瑚礁基于生态系统的管理方法的基础，但我们目前对鱼类的存在如何等同于珊瑚礁上的功能以及这种关系是否容易受到压力源的影响只有有限的了解。为了评估压力源塑造功能提供的能力，我们采用了一种多尺度方法，范围从澳大利亚大堡礁大陆架的数十公里，到珊瑚礁栖息地内的厘米级。在每个尺度上，我们通过珊瑚礁外科医生鱼（Ctenochaetus striatus）量化了模型功能（碎屑食性）的空间范围及其被沉积物塑造的潜力。在广泛的空间尺度上，C. striatus 的存在与藻类草皮沉积物负荷强烈相关，而在较小的空间尺度上，功能的提供似乎受到藻类草皮沉积物分布的限制。在所有情况下，沉积物负荷超过~250-500 g m 与鱼类丰度或摄食活动的明显下降相关，这表明一个常见的生态阈值在这个范围内。我们的结果揭示了功能提供的近因（鱼类）与功能提供的最终驱动因素（沉积物）之间复杂的功能动态，这强调了：a）鱼类存在与功能之间假定联系的弱点，以及 b）藻类草皮沉积物在塑造珊瑚礁过程方面的多尺度能力。除非直接的采掘活动（例如捕鱼）是珊瑚礁功能丧失的主要驱动因素，否则管理鱼类丰度不太可能产生预期的结果。它只解决了一个潜在的驱动因素。相反，需要管理提供功能的代理（例如鱼类）以及改变功能的驱动因素（例如沉积物）。
