Investigating preservation of stable isotope ratios in subfossil deep-sea proteinaceous coral skeletons as paleo-recorders of biogeochemical information over multimillennial timescales
Investigating preservation of stable isotope ratios in subfossil deep-sea proteinaceous coral skeletons as paleo-recorders of biogeochemical information over multimillennial timescales
复制标题
研究亚化石深海蛋白质珊瑚骨骼中稳定同位素比率的保存，作为数千年时间尺度生物地球化学信息的古记录器
DOI：
10.1016/j.gca.2022.09.023
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发表时间：
2022
影响因子：
5
通讯作者：
McCarthy, Matthew D.
中科院分区：
文献类型：
--
作者：
Glynn, Danielle S.;McMahon, Kelton W.;Sherwood, Owen A.;Guilderson, Thomas P.;McCarthy, Matthew D.
深海蛋白质珊瑚骨骼中的古代理记录可以重建百年至千年时间尺度上过去的海洋状况。通常回收的亚化石标本可能会将这些档案扩展到全新世。然而，从未检查过此类样本在数千年时间尺度上的蛋白质基质稳定性和稳定同位素代理的完整性。在这里，我们比较了来自中太平洋的活体采集和亚化石（~9.6–11.6 kyrs BP）Kulamanamana haumeaae深海珊瑚样本中的氨基酸（AA）组成以及本体和AA化合物特异性碳（δ13C）和氮（δ15N）同位素，以了解长期底栖氧暴露对初级珊瑚化学的影响。我们发现亚化石珊瑚最外层部分（0-10 mm）的 δ15N (∼7‰) 和 δ13C (∼2‰) 存在较大的耦合变化，这与蛋白质基质的广泛变化相一致。骨骼纹理的微观结构变化与较高的 C/N 比 (+0.8) 和基于同位素的氨基酸降解参数 (例如 ΣV ≥ 3) 一致，表明暴露于海水的戈尔贡宁发生广泛降解。然而，内部戈尔贡宁（>10毫米）保留了氨基酸分子组成（除了主要的甘氨酸损失）以及与活体采集的标本相似的体积和氨基酸特异性同位素值。这些结果表明，氨基酸的化合物特异性同位素分析可以重建清晰的成岩层之外的亚化石珊瑚的古海洋生物地球化学和生态系统信息，这可以通过 C/N 比和 ΣV 退化代理的评估轻松识别。
Paleoproxy records in deep-sea proteinaceous coral skeletons can reconstruct past ocean conditions on centennial to millennial time scales. Commonly recovered subfossil specimens could potentially extend these archives through the Holocene. However, protein matrix stability and integrity of stable isotope proxies over multi-millennial timescales in such specimens have never been examined. Here we compare amino acid (AA) composition together with bulk and AA compound-specific carbon (δ13C) and nitrogen (δ15N) isotopes in live-collected and subfossil (∼9.6–11.6 kyrs BP)Kulamanamana haumeaaedeep-sea coral specimens from the central Pacific to understand the effects of long-duration benthic oxic exposure on primary coral chemistry. We find large coupled shifts in bulk δ15N (∼7‰) and δ13C (∼2‰) in the outermost portion (0–10 mm) of the subfossil coral, coincident with extensive alteration of the protein matrix. Microstructural changes in skeletal texture coincide with higher C/N ratios (+0.8) and isotope-based amino acid degradation parameters (e.g. ΣV ≥ 3), indicating extensive degradation of seawater-exposed gorgonin. However, interior gorgonin (>10 mm) retained amino acid molecular compositions (with exception of major Glycine loss) and bulk and amino acid-specific isotopic values that were similar to live-collected specimens. These results indicate that compound-specific isotope analysis of amino acids can reconstruct paleo-oceanographic biogeochemical and ecosystem information in subfossil corals beyond a clear diagenetic horizon, which is easily identifiable from an evaluation of C/N ratios together with the ΣV degradation proxy.