Fine Maoz, Loya Yossi
Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, 69978, Israel.
Proc Biol Sci. 2002 Jun 22;269(1497):1205-10. doi: 10.1098/rspb.2002.1983.
Recent reports of worldwide coral bleaching events leading to devastating coral mortality have caused alarm among scientists and resource managers. Differential survival of coral species through bleaching events has been widely documented. We suggest that among the possible factors contributing to survival of coral species during such events are endolithic algae harboured in their skeleton, providing an alternative source of energy. We studied the dynamics of photosynthetic pigment concentrations and biomass of endoliths in the skeleton of the encrusting coral Oculina patagonica throughout a bleaching event. During repeated summer bleaching events these endolithic algae receive increased photosynthetically active radiation, increase markedly in biomass, and produce increasing amounts of photoassimilates, which are translocated to the coral. Chlorophyll concentrations and biomass of endoliths were 4.6 +/- 1.57 and 1570 +/- 427 microg cm(-2) respectively, in skeletons of relatively healthy colonies (0-40% bleaching) but up to 14.8 +/- 2.5 and 4036 +/- 764 microg cm(-2) endolith chlorophyll and biomass respectively, in skeletons of bleached colonies (greater than 40% bleaching). The translocation dynamics of (14)C-labelled photoassimilates from the endoliths to bleached coral tissue showed significantly higher 14C activity of the endoliths harboured within the skeletons of bleached corals than that of the endoliths in non-bleached corals. This alternative source of energy may be vital for the survivorship of O. patagonica, allowing gradual recruitment of zooxanthellae and subsequent recovery during the following winter.
近期有关全球珊瑚白化事件导致珊瑚大量死亡的报道引起了科学家和资源管理者的警觉。珊瑚物种在白化事件中的不同存活率已有广泛记录。我们认为，在这些事件中，有助于珊瑚物种存活的可能因素包括其骨骼中所含的内共生藻类，它们提供了一种替代能源。我们研究了在整个白化事件中，覆盖型珊瑚巴塔哥尼亚石珊瑚（Oculina patagonica）骨骼内共生藻类的光合色素浓度和生物量的动态变化。在反复出现的夏季白化事件中，这些内共生藻类接收到更多光合有效辐射，生物量显著增加，并产生越来越多的光合产物，这些产物会转移到珊瑚体内。相对健康的珊瑚群落（白化程度为0 - 40%）的骨骼中，内共生藻类的叶绿素浓度和生物量分别为4.6 +/- 1.57微克/平方厘米和1570 +/- 427微克/平方厘米，但在白化珊瑚群落（白化程度大于40%）的骨骼中，内共生藻类的叶绿素和生物量分别高达14.8 +/- 2.5微克/平方厘米和4036 +/- 764微克/平方厘米。从内共生藻类到白化珊瑚组织的（14）C标记光合产物的转移动态表明，白化珊瑚骨骼内的内共生藻类的14C活性显著高于未白化珊瑚中的内共生藻类。这种替代能源对于巴塔哥尼亚石珊瑚的存活可能至关重要，它使得虫黄藻能够逐渐重新定殖，并在随后的冬季实现恢复。
