2016年7月,加尔维斯顿东南约200公里处发生了严重的珊瑚礁无脊椎动物死亡事件。德州,在东花园银行,其中0.06平方公里区域内82%的珊瑚死亡。根据这次死亡事件后不久对死亡珊瑚和其他无脊椎动物的调查,应答者假设局部缺氧是最可能的直接原因.然而,没有溶解氧数据来检验这个假设,因为在花园银行保护区内没有持续监测氧气。这里,我们根据两年来在花卉花园银行的四次航行来量化微生物浮游生物群落多样性,包括首次观察到死亡事件后仅5至8天的巡游。与在非死亡率条件下收集的观察结果相反,温跃层中的微生物浮游生物群落差异富集了已知在氧气最小区域活跃和丰富的分类单元,或者已知在死亡事件后不久适应氧气限制(例如,SAR324,硫球蛋白科,Nitrosopelagicus,和ThermoplasmataMGII)。出乎意料的是,这些富集并没有局限在东岸,而是在整个研究区域普遍存在,这表明在死亡事件发生前后,温跃层中的溶解氧浓度普遍耗尽。水文分析显示,此时东岸南部的珊瑚礁(发生局部死亡事件的地方)在温跃层内是唯一的。我们的结果表明,微生物群落的时间监测如何成为解决与过去环境事件有关的问题的有用工具。重要性在2016年7月的墨西哥湾西北部,在东花园河岸珊瑚礁的一小部分地区,82%的珊瑚突然死亡,没有任何警告。氧气消耗被认为是原因。然而,有相当大的不确定性,因为从事件发生时没有氧气数据。微生物对氧气的变化敏感,可以用作氧气损失的生物指示剂。在这项研究中,我们分析了几年来在花园银行收集的水样中的微生物群落,包括死亡事件发生后不久。我们的发现表明,与正常情况相比,在死亡事件期间,深水层中氧耗竭普遍存在.水团的水文分析进一步揭示了一些低氧水可能涌向珊瑚礁。
In July 2016, a severe coral reef invertebrate mortality event occurred approximately 200 km southeast of Galveston, Texas, at the East Flower Garden Bank, wherein ∼82% of corals in a 0.06-km2 area died. Based on surveys of dead corals and other invertebrates shortly after this mortality event, responders hypothesized that localized hypoxia was the most likely direct cause. However, no dissolved oxygen data were available to test this hypothesis, because oxygen is not continuously monitored within the Flower Garden Banks sanctuary. Here, we quantify microbial plankton community diversity based on four cruises over 2 years at the Flower Garden Banks, including a cruise just 5 to 8 days after the mortality event was first observed. In contrast with observations collected during nonmortality conditions, microbial plankton communities in the thermocline were differentially enriched with taxa known to be active and abundant in oxygen minimum zones or that have known adaptations to oxygen limitation shortly after the mortality event (e.g., SAR324, Thioglobaceae, Nitrosopelagicus, and Thermoplasmata MGII). Unexpectedly, these enrichments were not localized to the East Bank but were instead prevalent across the entire study area, suggesting there was a widespread depletion of dissolved oxygen concentrations in the thermocline around the time of the mortality event. Hydrographic analysis revealed the southern East Bank coral reef (where the localized mortality event occurred) was uniquely within the thermocline at this time. Our results demonstrate how temporal monitoring of microbial communities can be a useful tool to address questions related to past environmental events. IMPORTANCE In the northwestern Gulf of Mexico in July 2016, ∼82% of corals in a small area of the East Flower Garden Bank coral reef suddenly died without warning. Oxygen depletion is believed to have been the cause. However, there was considerable uncertainty, as no oxygen data were available from the time of the event. Microbes are sensitive to changes in oxygen and can be used as bioindicators of oxygen loss. In this study, we analyze microbial communities in water samples collected over several years at the Flower Garden Banks, including shortly after the mortality event. Our findings indicate that compared to normal conditions, oxygen depletion was widespread in the deep-water layer during the mortality event. Hydrographic analysis of water masses further revealed some of this low-oxygen water likely upwelled onto the coral reef.