DeCarlo Thomas M, Harrison Hugo B
Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia.
Australian Research Council Centre of Excellence for Coral Reef Studies, University of Western Australia, Crawley, WA, Australia.
PeerJ. 2019 Aug 12;7:e7473. doi: 10.7717/peerj.7473. eCollection 2019.
Ocean warming threatens the functioning of coral reef ecosystems by inducing mass coral bleaching and mortality events. The link between temperature and coral bleaching is now well-established based on observations that mass bleaching events usually occur when seawater temperatures are anomalously high. However, times of high heat stress but without coral bleaching are equally important because they can inform an understanding of factors that regulate temperature-induced bleaching. Here, we investigate the absence of mass coral bleaching on the Great Barrier Reef (GBR) during austral summer 2004. Using four gridded sea surface temperature data products, validated with in situ temperature loggers, we demonstrate that the summer of 2004 was among the warmest summers of the satellite era (1982-2017) on the GBR. At least half of the GBR experienced temperatures that were high enough to initiate bleaching in other years, yet mass bleaching was not reported during 2004. The absence of bleaching is not fully explained by wind speed or cloud cover. Rather, 2004 is clearly differentiated from bleaching years by the slow speed of the East Australian Current (EAC) offshore of the GBR. An anomalously slow EAC during summer 2004 may have dampened the upwelling of nutrient-rich waters onto the GBR shelf, potentially mitigating bleaching due to the lower susceptibility of corals to heat stress in low-nutrient conditions. Although other factors such as irradiance or acclimatization may have played a role in the absence of mass bleaching, 2004 remains a key case study for demonstrating the dynamic nature of coral responses to marine heatwaves.
海洋变暖通过引发大规模珊瑚白化和死亡事件，威胁着珊瑚礁生态系统的功能。基于大规模白化事件通常发生在海水温度异常高时的观测结果，温度与珊瑚白化之间的联系现已得到充分证实。然而，高温胁迫但未发生珊瑚白化的时期同样重要，因为它们有助于了解调节温度诱导白化的因素。在这里，我们调查了2004年南半球夏季大堡礁未发生大规模珊瑚白化的情况。我们使用四种网格化海面温度数据产品，并与现场温度记录仪进行了验证，结果表明2004年夏季是卫星时代（1982 - 2017年）大堡礁最温暖的夏季之一。大堡礁至少一半区域经历的温度在其他年份足以引发白化，但2004年并未报告大规模白化事件。风速或云量并不能完全解释未发生白化的原因。相反，2004年与发生白化的年份明显不同之处在于大堡礁近海的东澳大利亚暖流（EAC）流速缓慢。2004年夏季EAC异常缓慢，可能抑制了富含营养的海水上升到大堡礁陆架，由于在低营养条件下珊瑚对热胁迫的敏感性较低，这可能减轻了白化现象。尽管其他因素如辐照度或适应性可能在未发生大规模白化过程中起到了作用，但2004年仍是证明珊瑚对海洋热浪反应动态性质的关键案例研究。
