Regulation and control of intracellular algae (equals zooxanthellae) in hard corals
Regulation and control of intracellular algae (equals zooxanthellae) in hard corals
复制标题
DOI：
10.1098/rstb.1997.0033
复制
发表时间：
1997-04-29
期刊：
影响因子：
--
通讯作者：
Yellowlees, D
中科院分区：
文献类型：
--
作者：
Jones, RJ;Yellowlees, D
为了研究algal(=zooxanthellae)的调控以及决定硬珊瑚中藻类密度的因素，定期测定了一群鹿角珊瑚(Acropora Formmosa)从珊瑚“漂白”事件(与压力相关的珊瑚-藻类共生解离)恢复后的分支嘴唇中的Zooxanthellas有丝分裂指数和释放率。根据漂白后恢复期内藻类分裂频率随密度的减少和藻类释放率的增加而建立的数学模型准确地预测了观察到的恢复期(大约20周)。模型表明：(I)群落从剩余的虫黄藻的分裂中恢复了其藻类种群，(Ii)虫黄藻的持续丧失显著地减缓了珊瑚的恢复。从恢复珊瑚中发生的内胚层过程和新形成的虫黄藻重新分布到非共生宿主细胞的角度，讨论了漂白珊瑚中健康的虫黄藻“矛盾地”丧失的可能原因。在恢复期结束时，当藻类的稳态密度为2.1x10(6)虫黄藻厘米(-2)时，虫黄藻必须在珊瑚组织中形成双层细胞，这与显微镜观察一致。具有较高藻类密度的邻近福尔摩沙殖民地的虫黄藻相对较小。结果表明，空间可获得性和藻类共生体的大小决定了珊瑚群体中的藻类密度。暴露在营养浓度升高的珊瑚中报告的藻类密度大幅增加(即藻类现存量增加两到五倍之间)与这一理论不一致。我们认为，这种幅度的增加是实验条件的产物：讨论了这一说法的原因。我们认为，珊瑚-藻类在非胁迫条件下共生的稳定性，以及珊瑚中虫黄藻密度在生长形式、深度和地理范围内的稳定性，与限制藻类密度的空间可获得性有关。然而，在这些密度下，虫黄藻具有与营养限制相一致的属性。
To examine alg al (= zooxanthellae) regulation and control, and the factors determining algal densities in hard corals, the zooxanthellae mitotic index and release rates were regularly determined in branch lips from a colony of a staghorn coral, Acropora formosa recovering from a coral 'bleaching' event (the stress-related dissociation of the coral-algal symbiosis). Mathematical models based upon density-dependent decreases in the algal division frequency and increases in algal release rates during the post-bleaching recovery period accurately predict the observed recovery period (approximate to 20 weeks). The models suggest that (i) the colony recovered its algal population from the division of the remaining zooxanthellae, and (ii) the continual loss of zooxanthellae significantly slowed the recovery of the coral. Possible reasons for the 'paradoxical' loss of healthy zooxanthellae from the bleached coral are discussed in terms of endodermal processes occurring in the recovering coral and the redistribution of newly formed zooxanthellae to aposymbiotic host cells. At a steady-state algal density of 2.1 x 10(6) zooxanthellae cm(-2) at the end of the recovery period, the zooxanthellae would have to form a double layer of cells in the coral tissues, consistent with microscopic observations. Neighbouring colonies of A. formosa with inherently higher algal densities possess proportionately smaller zooxanthellae. Results suggest that space availability and the size of the algal symbionts determines the algal densities in the coral colonies. The large increases in the algal densities reported in corals exposed to elevated nutrient concentrations (i.e. between a two- and five-fold increase in the algal standing stock) are not consistent with this theory. We suggest that increases of this magnitude are a product of the experimental conditions: reasons for this statement are discussed. We propose that the stability of the coral-algal symbiosis under non-stress conditions, and the constancy of zooxanthellae densities in corals reported across growth form, depth and geographic range, are related to space availability limiting algal densities. However, at these densities, zooxanthellae have attributes consistent with nutrient limitation.