The influence of turbidity on ancient and modern coral reefs

本文研究了两次新生代过热事件（全球变暖的时间间隔）中混浊水对珊瑚和珊瑚礁生存的作用。长期以来，人们认为多样化的珊瑚礁系统是一种仅限于清澈水域的现象。碎屑沉积物输入量高的地区被认为对珊瑚有害，因为水的透明度降低（减少珊瑚共生体的光合作用），细颗粒沉积物阻塞了无底栖动物的进食/呼吸装置，以及水柱中的营养物质和颗粒有机物增加（导致藻类广泛定植和珊瑚分类群窒息）。不幸的是，由于气候变暖导致水温升高，长时间无云地暴露在强烈的太阳辐射下，清澈的海水环境并没有提供缓解，因此，近年来，广泛的白化导致了热带珊瑚和珊瑚礁的广泛死亡。最近的研究表明，适度的浑浊（云量）可能会通过屏蔽珊瑚群免受高太阳辐射而降低珊瑚礁的压力，而不是窒息珊瑚礁。最近的一些研究已经确定了浑浊系统（浑浊水）珊瑚礁作为避难所，其中珊瑚礁生物群可能会撤退并在环境危机中生存下来。尽管浑浊水域的珊瑚礁很重要，但相对于清澈水域的珊瑚礁，人们对它们的了解很少。本研究计划的目的是调查浑浊水珊瑚礁在维持区域珊瑚礁健康和珊瑚礁动物群多样性方面所发挥的作用。研究了两个过热区间。古新世—始新世热最大值（PETM）—早始新世气候最佳值（EECO）区间（~ 5600万~ 4900万年前），是迄今为止地球上最温暖的区间。新特提斯地区（现代南欧）最新的古新世至始新世早期的珊瑚礁是我研究项目的重点，因为该地区是古近纪时期珊瑚礁多样性的中心，在纯碳酸盐和混合硅-塑料-碳酸盐序列中都有厚厚的垂直连续的、容易出现珊瑚礁的露头。所考虑的较年轻的间隔是中更新世到现代。在这里，我的重点是印度尼西亚松巴岛的东北海岸。松巴岛位于珊瑚三角区，这是地球上最多样化的海洋生态系统，拥有世界上76%的珊瑚物种和37%的珊瑚鱼物种。大面积的白化导致这些热带珊瑚和珊瑚礁大面积死亡。选择松巴岛是因为它有100万年的珊瑚礁隆起记录，包括古代和现代的浑浊水和清水珊瑚礁，并且位于瓦拉科海峡的一个岛屿上（一个岛屿丰富的地区，位于萨胡尔和巽他大陆架之间，在更新世期间暴露在海底）。

The role that turbid water has played in coral and coral reef survival through two Cenozoic hyperthermal events (temporal intervals of global warming) is investigated. Diverse coral reef systems were long considered to be phenomena limited to clear water settings. Areas of high clastic sediment input were considered to be harmful to corals due to reduced water transparency (reducing photosynthesis by coral symbionts), fine-grained sediment clogging the feeding / respiration apparatus of sessile benthic faunas and increased nutrients and particulate organics in the water column (which causes extensive algal colonization and smothering of coral taxa). Unfortunately, clear water settings provide no respite from increased water temperatures and prolonged, cloudless exposure to intense solar radiation that result from a warming climate and thus, in recent years extensive bleachings have resulted in the widespread demise of tropical corals and coral reefs. Recent studies have suggested that, rather than smothering reefs, moderate levels of turbidity (cloudiness) may lower reef stress by shielding coral taxa from high solar radiation. Several recent studies have identified turbid-system (murky water) coral reefs as refugia wherein reef biota may retreat and survive environmental crises. Despite the importance of turbid water coral reefs, they are poorly understood relative to their clear-water equivalents. The goal of this research program is to investigate the role that turbid water coral reefs play and have played in maintaining regional coral reef health and reef fauna diversity during hyperthermal events. Two hyperthermal intervals are investigated. The older interval is the Paleocene-Eocene Thermal Maximum (PETM) - Early Eocene Climate Optimum (EECO) interval (~56 to 49 million years ago), which includes the warmest interval on the earth up until the present day. Latest Paleocene to early Eocene reefs in the neoTethys region (modern southern Europe) are my focus for this research program as this area was the centre of reef diversity during the Paleogene and thick vertically continuous, reef-prone outcrop is available through both pure carbonate and mixed siliciclastic-carbonate successions. The younger interval considered is the Middle Pleistocene to Modern. Here my focus is on the northeastern coast of Sumba, Indonesia. Sumba occurs in the Coral Triangle, the most diverse marine ecosystem on the planet, hosting 76% of the world's coral species and 37% of coral fish species. extensive bleaching has resulted in the widespread demise of these tropical corals and coral reefs. The island of Sumba was chosen as it includes an one-million year record of uplifted coral reefs, includes ancient and modern turbid-water and clear-water coral reefs in close proximity and occurs on an island in the Wallacea straits (an island-rich region that occurs between the Sahul and Sunda shelves, which were subaerially exposed during the Pleistocene).