Coccolith Sr/Ca as a new indicator of coccolithophorid calcification and growth rate
Coccolith Sr/Ca as a new indicator of coccolithophorid calcification and growth rate
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DOI：
10.1029/1999gc000015
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发表时间：
2000-05-30
影响因子：
3.5
通讯作者：
Schrag, Daniel P.
中科院分区：
文献类型：
--
作者：
Stoll, Heather M.;Schrag, Daniel P.
在赤道东太平洋的核心顶部沉积物中分离出的多种颗石在整个赤道上涌带的Sr/Ca比值中显示出类似于15%的变化，其中Sr/Ca在赤道处最高，并且在离轴处降低。这些变化不可能是由于海水中Sr/Ca的变化造成的，海水中Sr/Ca的变化在表层海洋中不到2%。在Sr/Ca的变化的颗石沉积物是类似的变化，初级生产力和烯酮估计的颗石生长速率在上覆的地表沃茨和CaCO 3降雨率在沉积物陷阱测量。由于这些关系，因为钙化率施加强有力的控制Sr/Ca在非生物成因方解石，我们认为，所观察到的Sr/Ca的变化可能强烈控制的颗石生长和钙化率，虽然温度也可能影响颗石Sr/Ca的程度较低。溶解强度和颗石组合的变化似乎施加轻微的影响，如果有的话，在这些沉积物芯顶部的颗石Sr/Ca。如果进一步的工作证实了颗石Sr/Ca和颗石生产力之间的关系，Sr/Ca记录过去的变化，颗石生产力可能是有用的重建过去的变化在雨的有机碳酸盐碳，深海pH值和大气和海洋之间的二氧化碳分配的重要控制。此外，颗石锶/钙可能提供了一个独立的记录，过去的变化，在颗石藻生长速率，这与数据相结合的碳同位素分馏在颗石藻有机质可能允许更可靠的计算过去溶解的CO2在海洋表面。
Polyspecific coccolith separates from core top sediments in the eastern equatorial Pacific show variations of similar to 15% in Sr/Ca ratios across the equatorial upwelling zone, with Sr/Ca highest at the equator and decreasing off-axis. These variations cannot be due to changes in the Sr/Ca of seawater, which varies by less than 2% in the surface ocean. Variations in Sr/Ca of coccolith sediments are similar to variations in primary productivity and alkenone-estimated coccolithophorid growth rates in overlying surface waters and to CaCO3 rain rates measured in sediment traps. Because of these relationships and because calcification rate exerts a strong control on Sr/Ca in abiogenic calcites, we suggest that the observed Sr/Ca variations in coccoliths may be strongly controlled by coccolithophorid growth and calcification rates, although temperature may also influence coccolith Sr/Ca to a lesser degree. Changes in dissolution intensity and coccolith assemblages appear to exert a minor influence, if any, on coccolith Sr/Ca in these sediment core tops. If further work confirms relationships between coccolith Sr/Ca and coccolithophorid productivity, Sr/Ca records of past changes in coccolithophorid productivity may be useful in reconstructing past variations in the rain ratio of organic to carbonate carbon, an important control on deep ocean pH and partitioning of CO2 between the atmosphere and ocean. In addition, coccolith Sr/Ca might provide an independent record of past changes in coccolithophorid growth rates, which in combination with data on the carbon isotopic fractionation in coccolithophorid organic matter may permit more reliable calculations of past dissolved CO2 in the surface ocean.