Abstract Coccolithophores are one of the most abundant and widespread groups of calcifying plankton and have attracted extensive study in terms of their likely response to ocean acidification. Conflicting results concerning coccolithophore calcification have been reported from both experimental and field studies. Due to their minute size, it is difficult to estimate the amount of calcite in coccoliths. Here we apply the SYRACO system to analyzing the weights and lengths of coccoliths produced by the dominant coccolithophore family Noelaerhabdaceae. We obtain high-resolution coccolith weight and length records of GEO (Gephyrocapsa oceanica) and SPC (Emiliania huxleyi and small Gephyrocapsa spp.) groups from sediment core MD05-2904 in the northern South China Sea (SCS) over the past 200 kyr. A calcification index (CI) based on the coccolith weight and length is applied to evaluate the changes in coccolithophore calcification. The two groups of coccolith weights / CIs show different patterns on long term variations and during the last two terminations. We compare the coccolith weight and CI records with the environmental variables and carbonate chemistry parameters calculated in the same core. Our data reveals that sea surface temperature and insolation have weak correlations to coccolith weight and CI on long-term variations. The SPC weight / CI are correlated with the seawater pH and pCO2 variations while the GEO weight/ CI are more related to the nutrient variations. This implies a more significant role of ocean carbonate chemistry in the calcification of less calcified coccolithophores and nutrient concentration in the heavier calcifying coccolithophores.

中文翻译：

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南海北部晚第四纪石块重量变化及其环境控制

摘要 球石藻是钙化浮游生物中最丰富和分布最广的群体之一，它们对海洋酸化的可能反应引起了广泛的研究。实验和实地研究都报告了有关颗石藻钙化的相互矛盾的结果。由于它们的尺寸很小，很难估计球石中方解石的数量。在这里，我们应用 SYRACO 系统来分析主要的球石藻科 Noelaerhabdaceae 产生的球石的重量和长度。我们从南海北部 (SCS) 的沉积岩芯 MD05-2904 中获得了过去 200 kyr 的 GEO (Gephyrocapsa oceanica) 和 SPC (Emiliania huxleyi and small Gephyrocapsa spp.) 群的高分辨率球石重量和长度记录。应用基于颗石重量和长度的钙化指数 (CI) 来评估颗石藻钙化的变化。两组颗石重量/CI 在长期变化和最后两个终止期间显示出不同的模式。我们将球石重量和 CI 记录与在同一岩心中计算的环境变量和碳酸盐化学参数进行比较。我们的数据显示，海面温度和日照与长期变化中的球石重量和 CI 的相关性较弱。SPC 权重 / CI 与海水 pH 值和 pCO2 变化相关，而 GEO 权重 / CI 与养分变化更相关。