Deep Heat: A Comparison of Water Temperature, Anemone Bleaching, Anemonefish Density and Reproduction between Shallow and Mesophotic Reefs
Deep Heat: A Comparison of Water Temperature, Anemone Bleaching, Anemonefish Density and Reproduction between Shallow and Mesophotic Reefs
复制标题
深热：浅水和中光珊瑚礁水温、海葵白化、海葵鱼密度和繁殖的比较
作者：
A. Haguenauer;F. Zuberer;G. Siu;Daphne Cortese;R. Beldade;S. Mills
法属波利尼西亚正在经历由与气候变化有关的热异常和海洋热浪引发的浅水珊瑚白化事件的增加，这一趋势在世界各地都在复制。由于海面热异常被认为随着深度的增加而减弱，中温性深礁被假定为躲避人为和自然干扰的避难所，即“深礁避难所假说”(DRRH)。然而，支持DRRH的证据要么没有定论，要么相互矛盾。我们通过研究DRRH的四个假设来解决这个问题，重点是海葵和海葵之间的共生关系。首先，我们比较了2011-2020年莫雷亚岛浅层(8米)和中层(50米)的长期温度条件。其次，我们比较了法属波利尼西亚三个群岛浅礁和中礁(低至60米)上橙鳍海葵的密度。最后，我们比较了浅水礁和中温礁之间海葵漂白和海葵繁殖的百分比。我们发现，在冬季较凉爽的月份，水柱混合良好，两个深度之间的温差只有0.19°C，但在较温暖的夏季，混合减少，导致温差0.71-1.03°C。然而，在热异常期间，尽管到达中层珊瑚礁的温暖表层水域有一段时间滞后，但最终在8米和50米处的水温上升了1.0摄氏度，使这两个深度的温度都超过了漂白阈值。因此，在这些热异常期间，在中温礁观察到了海葵漂白，但与较浅水域的漂白百分比相比，海葵漂白得到了缓冲，后者几乎是浅水漂白的五倍。我们在法属波利尼西亚各地进行的大规模采样发现，在两个高岛和一个环礁跨越两个群岛的中温区发现了橙鳍海葵A.chrysopterus，将其水深极限扩大到60米；然而，橙鳍海葵的密度与浅水区相似，或比浅水区低25-92倍。在50m处观察到三次产卵事件，其发生频率与同一日期在浅滩珊瑚礁发生的频率相似。我们对中生礁温度异常和漂白的发现，再加上中游种群中主要密度较低的海葵，表明中生礁仅显示出有限的能力来提供躲避人为和自然干扰的能力。
French Polynesia is experiencing increasing coral bleaching events in shallow waters triggered by thermal anomalies and marine heatwaves linked to climate change, a trend that is replicated worldwide. As sea surface thermal anomalies are assumed to lessen with depth, mesophotic deep reefs have been hypothesized to act as refuges from anthropogenic and natural disturbances, the ‘deep reef refugia hypothesis’ (DRRH). However, evidence supporting the DRRH is either inconclusive or conflicting. We address this by investigating four assumptions of the DRRH focusing on the symbiotic association between anemones and anemonefish. First, we compare long-term temperature conditions between shallow (8 m) and mesophotic sites (50 m) on the island of Moorea from 2011–2020. Second, we compare the densities of the orange-fin anemonefish, Amphiprion chrysopterus between shallow and mesophotic (down to 60 m) reefs across three archipelagos in French Polynesia. Finally, we compare the percentage of anemone bleaching, as well as anemonefish reproduction, between shallow and mesophotic reefs. We found that the water column was well mixed in the cooler austral winter months with only a 0.19 °C difference in temperature between depths, but in the warmer summer months mixing was reduced resulting in a 0.71–1.03 °C temperature difference. However, during thermal anomalies, despite a time lag in warm surface waters reaching mesophotic reefs, there was ultimately a 1.0 °C increase in water temperature at both 8 and 50 m, pushing temperatures over bleaching thresholds at both depths. As such, anemone bleaching was observed in mesophotic reefs during these thermal anomalies, but was buffered compared to the percentage of bleaching in shallower waters, which was nearly five times greater. Our large-scale sampling across French Polynesia found orange-fin anemonefish, A. chrysopterus, in mesophotic zones in two high islands and one atoll across two archipelagos, extending its bathymetric limit to 60 m; however, orange-fin anemonefish densities were either similar to, or 25–92 times lower than in shallower zones. Three spawning events were observed at 50 m, which occurred at a similar frequency to spawning on shallower reefs at the same date. Our findings of thermal anomalies and bleaching in mesophotic reefs, coupled with mainly lower densities of anemonefish in mesophotic populations, suggest that mesophotic reefs show only a limited ability to provide refugia from anthropogenic and natural disturbances.
影响因子：
4.9
作者：
Beldade, Ricardo;Holbrook, Sally J.;Bernardi, Giacomo
通讯作者：
Bernardi, Giacomo
影响因子：
30.7
作者：
Smale, Dan A.;Wernberg, Thomas;Moore, Pippa J.
通讯作者：
Moore, Pippa J.