Quantifying ENSO-related bleaching on nearshore, turbid-zone coral reefs: a test of the turbid-zone reef climate change refugia hypothesis.

在过去的两个月里，越来越多的报道称，目前的厄尔尼诺现象导致澳大利亚大堡礁（GBR）沿着大规模珊瑚白化，航空调查报告称，超过90%的珊瑚礁正在白化，这些珊瑚礁上超过50%的珊瑚已经死亡。然而，这些调查无法评估近岸浊流区珊瑚礁的情况，首先是因为浊流水平阻碍了空中评估，其次是因为几乎没有生态数据可以比较变化。然而，这些浊流区珊瑚礁上珊瑚的漂白反应具有重大的科学意义。这种兴趣特别涉及到这样一种假设，即可能有特定的海洋环境，可能作为重要的避难所网站从漂白，即，这些环境更有效地缓冲了表面变暖，使珊瑚种群基本上不受影响。珊瑚礁形成在良好的冲洗，高度浑浊的设置是这样一个候选位置，这些避难所。增加漂白弹性已被假设，因为水中的高颗粒含量可能会限制紫外线应力，因为珊瑚可能更容易切换到主要异养喂养模式-原因是增强保护免受最初假设在2000年代初的热应力事件。然而，最近的建模现在提供了一个全球规模的框架，通过该框架可以确定这种潜在避难所的空间范围。然而，缺乏的是任何经验性的实地证据，确切地表明这些浊流区珊瑚礁实际上能够承受主要的珊瑚漂白事件。毫无疑问，对这些浊流带珊瑚礁研究最好的是那些沿着GBR近岸区域的珊瑚礁，自2006年以来，PI及其团队一直在集中研究这些珊瑚礁。这项工作主要集中在评估珊瑚礁生长的速度和风格，但我们最近的工作已经作为其核心目标的空间范围和当代生态结构的评估，这些珊瑚礁。我们在GBR中部开展了前所未有的测绘和生态勘测活动，收集了超过130公里的海底条带勘测数据和超过4，500个视频静态样方。由此产生的数据集使我们能够开发高分辨率的珊瑚礁结构和生态组成的地图，这表明，尽管其狭窄的测深范围，这些珊瑚礁的特点是由一个明确的深度控制的生态分区，他们表现出高活珊瑚覆盖（平均值：38%，但高达~80%）。因此，我们在一个独特的位置，以定量评估在何种程度上，这一重大漂白事件影响了这些浊流区的珊瑚礁，并测试最近提出的假设，这种珊瑚礁可能会作为关键的气候变化refugia sites.In这个项目中，我们将进行快速评估的影响漂白的浊流区珊瑚礁附近的Paluma浅滩（中央哈利法克斯湾）。我们将使用遥控水下视频调查方法重新检查一套六个邻近的珊瑚礁，并收集生态数据，沿着复制横断面跨越每个珊瑚礁。视频数据将用于确定物种丰度和漂白强度。这将使我们能够确定：1）漂白引起的死亡的总程度; 2）特定珊瑚物种受到影响的程度;以及3）对珊瑚礁结构复杂性和多样性的任何直接影响。我们亦会在其他浊流区珊瑚礁进行类似的评估，这些珊瑚礁是我们较早前研究的重点，例如：更远的北部在敦克岛周围，南部在中礁-这些珊瑚礁占据类似的地貌和沉积环境的Paluma复杂。因此，这项工作将不仅提供有关浊区珊瑚礁漂白程度的数据，而且还提供了一个强有力的假设，即浊区珊瑚礁可能形成关键的气候变化避难所。

Over the last two months there have been increasing reports of the current El Niño causing massive coral bleaching along Australia's Great Barrier Reef (GBR), with aerial surveys reporting that >90% of reefs are bleaching, and with more that 50% of corals on these reefs already dead. However, these surveys cannot assess what is happening on the nearshore turbid-zone reefs, firstly because turbidity levels inhibit aerial assessments, and secondly because there is little ecological data against which to compare change. The bleaching response of corals on these turbid-zone reefs is however of significant scientific interest. This interest relates specifically to the hypothesis that there may be particular marine environments that might act as important refugia sites from bleaching i.e., settings that are more effectively buffered from surface warming such that coral populations remain largely unaffected. Reefs forming in well-flushed, highly turbid settings are one such candidate location for these refugia. Increased bleaching resilience has been hypothesized because high particulate content in the water may limit UV stress, and because the corals may be more readily able to switch to predominantly heterotrophic feeding modes - reasons for enhanced protection from thermal stress events that were initially hypothesised in the early 2000's. However, recent modelling now provides a global-scale framework through which the spatial extent of such potential refugia can be defined. What is lacking however is any empirical field evidence definitively showing that these turbid-zone reefs are actually able to withstand major coral bleaching events. Without doubt the best studied of these turbid-zone reefs are those along the nearshore areas of the GBR, which have been the focus of intensive study by the PI and his group since 2006. This work has largely focused on assessing rates and styles of reef growth, but our most recent work has had as its central aim an assessment of the spatial extent and contemporary ecological structure of these reefs. Working at sites in the central GBR we have undertaken an unprecedented mapping and ecological surveying campaign, collecting >130 km of seafloor swath survey data and >4,500 video still quadrats. The resulting datasets have enabled us to develop high resolution maps of reef structure and ecological composition, which show that despite their narrow bathymetric extent, these reefs are characterised by a clear depth-controlled ecological zonation, and that they exhibit high live coral cover (mean: 38%, but up to ~80%). We are thus in a unique position to quantitatively assess the extent to which this major bleaching event has impacted these turbid-zone reefs, and to test the recently proposed hypothesis that such reefs may act as critical climate change refugia sites.In this project we will undertake a rapid assessment of the impacts of bleaching on the turbid-zone reefs in the vicinity of Paluma Shoals (central Halifax Bay). We will re-examine a suite of six proximal reefs using remotely-operated underwater video survey methods and collect ecological data along replicate transects across each reef. Video data will be used to determine species abundance and bleaching intensity. This will allow us to ascertain: 1) the total extent of bleaching-induced mortality; 2) the extent to which specific coral species have been impacted; and 3) any immediate impacts on the structural complexity and diversity of the reefs. We will also undertake comparable assessments at other turbid-zone reefs which have been the focus of our earlier studies e.g., further north around Dunk Island and to the south at Middle Reef- these reefs occupying similar geomorphic and sedimentary settings to the Paluma complex. The work would thus deliver not only data on the extent of turbid-zone reef bleaching, but also provide a robust test of the hypothesis that turbid-zone reefs may form critical climate change refugia sites.