ABSTRACT

Staghorn corals represent dominant reef-builders in lagoons and back reefs in Guam. These habitats experience peak seawater temperatures close to 36°C during the hottest months of the year which causes increasingly frequent bleaching episodes that have led to major staghorn coral declines. To study the photo-physiological response of staghorn corals to bleaching conditions, pulse amplitude modulated (PAM) fluorometry was used to record signatures of chlorophyll fluorescence in Acropora cf. pulchra. Fragments of A. cf. pulchra were subjected to a week-long heat treatment some 2–3°C above average ambient seawater temperatures of 30°C; a four-week long recovery period at ambient temperatures followed treatment. While heat-treated coral fragments exposed to full sun responded with immediate and lasting declines in photosynthetic efficiency, shading of coral fragments largely mitigated the effects of elevated seawater temperatures. Of particular concern to reef management efforts is the finding that the strongest effects of heat stress were observed during the recovery period following the initial heat stress. Indeed, it took three times as long as the initial stress event lasted for photosynthesis to return to baseline levels. This lengthy recovery period appears to be driven by photodamage, likely requiring time-consuming protein synthesis-dependent repair of damaged photosystems and replacement of damaged zooxanthellae. These results highlight the importance of developing and implementing coral bleaching intervention efforts well beyond the end of bleaching conditions to facilitate recovery of affected reefs.

摘要

鹿角珊瑚代表关岛泻湖和后礁的主要造礁者。在一年中最热的月份中，这些栖息地的海水峰值温度接近36 ° C，这导致漂白事件越来越频繁，导致鹿角珊瑚的数量大幅减少。为了研究鹿角珊瑚对漂白条件的光生理响应，使用脉冲幅度调制（PAM）荧光法记录了Acropora cf中叶绿素荧光的特征。pulchra。A. cf.的片段 对pulchra进行了为期一周的热处理，比周围平均海水温度30 ° C高2–3 ° CC; 处理后，在环境温度下恢复四周之久。暴露于充足阳光下的经过热处理的珊瑚碎片的光合作用效率立即持续下降，而珊瑚碎片的遮荫则在很大程度上减轻了海水温度升高的影响。珊瑚礁管理工作特别关注的发现是，在初始热应力之后的恢复期内，热应力的作用最强。的确，只要初始胁迫事件持续了三倍，光合作用就恢复到基线水平。这个漫长的恢复期似乎是由光损伤驱动的，可能需要耗时的蛋白质合成依赖性修复受损的光系统和更换受损的黄原虫。