Influence of temperature and CO2 on the strontium and magnesium composition of coccolithophore calcite
Influence of temperature and CO2 on the strontium and magnesium composition of coccolithophore calcite
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DOI：
10.5194/bg-11-1065-2014
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发表时间：
2014-01-01
期刊：
影响因子：
4.9
通讯作者：
Stoll, H. M.
中科院分区：
文献类型：
--
作者：
Mueller, M. N.;Lebrato, M.;Stoll, H. M.
海洋钙质沉积物为古海洋学研究提供了重要的基础，其目的是重建过去的海洋环境和了解关键的地球化学元素循环。钙化单细胞浮游植物（颗石藻）是光合作用和真光层方解石（颗石藻）生产的碳和钙循环以及随后长期沉积和埋藏到海洋沉积物中的主要贡献者。在这里，我们提出的数据从控制实验室实验四颗石物种和二价阳离子（Sr，Mg和Ca）的分配在颗石和细胞生理（生长，钙化和光合作用）之间的关系进行说明。在不同的海水温度和碳酸盐化学条件下培养颗石藻。锶的分配系数（DSr）与二氧化碳（pCO（2））和温度呈正相关，但没有显示出一致的关系，颗粒有机和无机碳的生产率。此外，DSr与细胞生长率呈正相关时，由温度驱动，但没有相关性时，生长率的变化是pCO（2）诱导的。我们的研究结果证明了环境强迫和生理控制对颗石方解石中锶分配的复杂相互作用，以及对高pCO（2）环境中颗石Sr/Ca比值的挑战性解释（例如，G.古新世-始新世热极大期）。镁的分配系数（D-Mg）表现出种间差异，且在营养限制下有所升高。未观察到球石DMg与温度之间的决定性相关性，但pCO 2诱导球石DMg呈上升趋势。有趣的是，最好的相关性被发现之间的颗石DMg和叶绿素a的生产，这表明叶绿素a和方解石相关的镁来源于相同的细胞内池。这些和以前的研究结果表明，镁是通过不同的途径比钙和锶运输到细胞和钙化的网站。因此，颗石镁/钙比应从海水镁/钙比解耦。这项研究提供了一个扩展的洞察力的驱动因素影响的颗石镁/钙比，并应考虑为未来的古代理校准。
Marine calcareous sediments provide a fundamental basis for palaeoceanographic studies aiming to reconstruct past oceanic conditions and understand key biogeochemical element cycles. Calcifying unicellular phytoplankton (coccolithophores) are a major contributor to both carbon and calcium cycling by photosynthesis and the production of calcite (coccoliths) in the euphotic zone, and the subsequent long-term deposition and burial into marine sediments. Here we present data from controlled laboratory experiments on four coccolithophore species and elucidate the relation between the divalent cation (Sr, Mg and Ca) partitioning in coccoliths and cellular physiology (growth, calcification and photosynthesis). Coccolithophores were cultured under different seawater temperature and carbonate chemistry conditions. The partition coefficient of strontium (DSr) was positively correlated with both carbon dioxide (pCO(2)) and temperature but displayed no coherent relation to particulate organic and inorganic carbon production rates. Furthermore, DSr correlated positively with cellular growth rates when driven by temperature but no correlation was present when changes in growth rates were pCO(2)-induced. Our results demonstrate the complex interaction between environmental forcing and physiological control on the strontium partitioning in coccolithophore calcite and challenge interpretations of the coccolith Sr/Ca ratio from high-pCO(2) environments (e. g. Palaeocene-Eocene thermal maximum). The partition coefficient of magnesium (D-Mg) displayed species-specific differences and elevated values under nutrient limitation. No conclusive correlation between coccolith DMg and temperature was observed but pCO2 induced a rising trend in coccolith DMg. Interestingly, the best correlation was found between coccolith DMg and chlorophyll a production, suggesting that chlorophyll a and calcite associated Mg originate from the same intracellular pool. These and previous findings indicate that Mg is transported into the cell and to the site of calcification via different pathways than Ca and Sr. Consequently, the coccolith Mg/Ca ratio should be decoupled from the seawater Mg/Ca ratio. This study gives an extended insight into the driving factors influencing the coccolith Mg/Ca ratio and should be considered for future palaeoproxy calibrations.