Interplay of host morphology and symbiont microhabitat in coral aggregations
Interplay of host morphology and symbiont microhabitat in coral aggregations
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DOI：
10.1007/s002270050219
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发表时间：
1997-11-01
期刊：
影响因子：
2.4
通讯作者：
Sebens, KP
中科院分区：
文献类型：
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作者：
Helmuth, BST;Timmerman, BEH;Sebens, KP
伯利兹珊瑚礁珊瑚 Agaricia tenuifolia Dana 形成聚集体，其中一排排薄而直立的叶片彼此排列在一起。平均而言，叶片之间的间距随着深度的增加而增加，因此随着环境辐照度的减少而增加。我们设计并制造了一个小型、廉价的测光计，并用它来量化分支间距对距分支尖端不同距离的菌落内光照水平的影响。同时，我们测量了从 15 至 17 m 处收集的细枝间距（小于或等于 3 cm）与宽枝间距（大于或等于 6 cm）的珊瑚枝中提取的共生甲藻（虫黄藻）的光合色素浓度和种群密度，以及从 1 至 2 m 处收集的细枝间距的珊瑚枝中提取的共生甲藻（虫黄藻）的光合色素浓度和种群密度。随着分枝间距的缩小以及距分枝尖端的距离的增加，光照水平显着降低。总细胞色素浓度（叶绿素 a、c(2) 和多甲素）以及叶绿素 a:c(2) 和叶绿素 a:多甲素比率均随着距分支尖端的距离而显着增加，表明各个分支内的光适应存在非常局部的差异。来自具有宽间隔分支的菌落的虫黄藻表现出显着较低的叶绿素 a:c(2) 和叶绿素 a:多甲素比率，并且其种群密度显着高于来自在相同深度 (15 m) 收集的具有紧密间隔分支的菌落的虫黄藻。从浅层环境（1 至 2 m）收集的紧密分布的菌落显示出与来自较深水域（15 m）的宽间隔菌落相似的色素比例，但将虫黄藻种群维持在与来自较深水域的紧密分枝菌落相似的水平。因此，菌落形态的变化（分支间距和距分支尖端的距离）可以影响共生体生理学，其影响方式相当于水深增加超过 15 m。这些结果表明，宿主的形态可以在非常小的空间尺度上强烈决定其共生体的微生境，而虫黄藻反过来可以根据这些改变的物理条件表现出陡峭的梯度。
The Belizean reef coral Agaricia tenuifolia Dana forms aggregations in which rows of thin, upright blades line up behind each other. On average, the spacing between blades increases with depth and hence with decreasing ambient irradiance. We designed and built a small, inexpensive light meter and used it to quantify the effect of branch spacing on light levels within colonies at varying distances from branch tips. Concurrently, we measured photosynthetic pigment concentrations and population densities of symbiotic dinoflagellates (zooxanthellae) extracted from coral branches of colonies with tight (less than or equal to 3 cm) vs wide (greater than or equal to 6 cm) branch spacing, collected at 15 to 17 m and from colonies with tight branch spacing collected at 1 to 2 m. Light levels decreased significantly with tighter branch spacing and with distance from the branch tips. Total cellular pigment concentrations (chlorophylls a, c(2) and peridinin) as well as chlorophyll a:c(2) and chlorophyll a:peridinin ratios all increased significantly with distance from the branch tip, indicating very localized differences in photoacclimation within individual branches. Zooxanthellae from colonies with widely-spaced branches displayed significantly lower chlorophyll a:c(2) and chlorophyll a:peridinin ratios, and were present at significantly higher population densities than those from colonies with tightly-spaced branches collected at the same depth (15 m). Tightly-spaced colonies collected from shallow environments (1 to 2 m) displayed pigment ratios similar to those from widely-spaced colonies from deeper water (15 m), but maintained zooxanthellae populations at levels similar to those in tightly-branched colonies from deeper water. Thus, variation in colony morphology (branch spacing and distance from branch tip) can affect symbiont physiology in a manner comparable to an increase of over 15 m of water depth. These results show that a host's morphology can strongly determine the microhabitat of its symbionts over very small spatial scales, and that zooxanthellae can in turn display steep gradients in concordance with these altered physical conditions.