Stable isotopes (δ13C and δ15N) of organic matrix from coral skeleton
Stable isotopes (δ13C and δ15N) of organic matrix from coral skeleton
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DOI：
10.1073/pnas.0408921102
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发表时间：
2005-02-01
影响因子：
11.1
通讯作者：
Allemand, D
中科院分区：
文献类型：
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作者：
Muscatine, L;Goiran, C;Allemand, D
造礁珊瑚在营养匮乏的热带水域中的进化成功归因于内共生的甲藻。藻类将光合产物释放给珊瑚动物细胞，增加营养通量，并提高珊瑚的钙化速率。稳定同位素δ(13)C和δ(18)O的自然丰度为有关光合共生对珊瑚骨骼碳酸钙中碳和氧来源的影响的现代和古生物学问题提供了答案。在此我们比较了17种共生和非共生珊瑚，以确定光合共生的证据是否出现在有机骨骼部分（珊瑚骨骼有机基质，OM）的稳定同位素（δ(13)C和δ(15)N）中。共生和非共生珊瑚的平均OM δ(13)C相似（-26.08‰对-24.31‰），但前者的平均OM δ(15)N的N - 15显著贫化（4.09‰），相对于后者（12.28‰），这表明藻类对OM合成有影响，并揭示OM δ(15)N可作为光合共生的一个指标。为了回答一个关于造礁珊瑚光合共生起源的重要古生物学问题，我们将这一指标测试应用于一种来自三叠纪（2.4亿年前）的保存有OM的化石珊瑚（大厚壁珊瑚，Pachythecalis major）。平均OM δ(15)N为4.66‰，表明大厚壁珊瑚是光合共生的。结果表明，共生藻类通过促进骨骼OM的合成来增强珊瑚的钙化，而且它们可能早在三叠纪就已经这样做了。
The evolutionary success of reef-building corals in nutrient-poor tropical waters is attributed to enclosymbiotic dinoflagellates. The algae release photosynthetic products to the coral animal cells, augment nutrient flux, and enhance the rate of coral calcification. Natural abundance of stable isotopes delta(13)C and delta(18)O provides answers to modern and paleobiological questions about the effect of photosymblosis on sources of carbon and oxygen in coral skeletal calcium carbonate. Here we compare 17 species of symbiotic and nonsymbiotic corals to determine whether evidence for photosymbiosis appears in stable isotopes (delta(13)C and delta(15)N) of an organic skeletal compartment, the coral skeletal organic matrix (OM). Mean OM delta(13)C in symbiotic and nonsymbiotic corals was similar (-26.08parts per thousand vs. -24.31parts per thousand), but mean OM delta(15)N was significantly depleted in N-15 in the former (4.09parts per thousand) relative to the latter (12.28parts per thousand), indicating an effect of the algae on OM synthesis and revealing OM delta(15)N as a proxy for photosymbiosis. To answer an important paleobiological question about the origin of photosymbiosis in reef-building corals, we applied this proxy test to a fossil coral (Pachythecalis major) from the Triassic (240 million years ago) in which OM is preserved. Mean OM delta(15)N was 4.66parts per thousand, suggesting that P. major was photosymbiotic. The results show that symbiotic algae augment coral calcification by contributing to the synthesis of skeletal OM and that they may have done so as early as the Triassic.