| Ma Ruigang,Yang Haizhang,Jin Xiaobo,Zhao Zhao,Zhang Gongcheng,Liu Chuanlian. 2020. Calcareous nannofossil changes in the Early Oligocene linked to nutrient and atmospheric CO2. Acta Oceanologica Sinica, 39(10):70－80 |
| Calcareous nannofossil changes in the Early Oligocene linked to nutrient and atmospheric CO2 |
| 早渐新世钙质超微化石演变与营养盐及二氧化碳关系 |
| Received:March 18, 2020 |
| DOI：10.1007/s13131-020-1661-6 |
| Key words:coccolithophore assemblage change weathering intensity carbon concentrating mechanism northern South China Sea |
| 中文关键词: 颗石藻 群落变化 风化强度 碳浓缩机制 南海北部 |
| 基金项目: |
| Author Name | Affiliation | E-mail | | Ma Ruigang | State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China | | | Yang Haizhang | CNOOC Research Institute Co., Ltd., Beijing 100027, China | | | Jin Xiaobo | State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China | | | Zhao Zhao | CNOOC Research Institute Co., Ltd., Beijing 100027, China | | | Zhang Gongcheng | CNOOC Research Institute Co., Ltd., Beijing 100027, China | | | Liu Chuanlian | State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China | liucl@tongji.edu.cn |
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| Abstract: |
| Rapid changes on nutrient supply and CO2 concentration that occurred in the northern South China Sea (SCS) during the Early Oligocene, provides an ideal natural laboratory, allowing us to peer into the coccolithophores’ physiology in the geological records. In this study, we established a new nannofossil assemblage index, termed as E* ratio, which is calculated by the relative abundance of eutrophic taxa and meso-oligotrophic taxa (${E^*}=\frac{e}{{e + c}}\times100$, where e is eutrophic taxa, and c is meso-oligotrophic taxa). Eutrophic taxa include small Reticulofenestra, Reticulofenestra lockeri group, Reticulofenestra bisecta group and Coccolithus pelagicus group, while meso-oligotrophic taxa include Cyclicargolithus spp. The E* ratio is well correlated with nutrient proxy during the Early Oligocene, while with different covarying patterns under the higher and lower CO2 condition. By comparing the assemblage changes to the published data, we suggest that coccolithophores may change the way they use carbon source and nutrient with the decline of CO2. Furthermore, this implies a possible initiation of the carbon concentrating mechanism. |
| 中文摘要: |
| 南海北部早渐新世发生明显的营养供给和二氧化碳浓度的变化，相关地质记录为研究颗石藻的生理机制提供了理想的自然实验室。在本研究中，我们建立了一个新的颗石藻群落演化的指标，定义为E*比值。该比值由富营养属种和中等-贫营养属种的相对丰度计算而得（E*=e/(e+c)×100，e代表富营养属种，c代表中等-贫营养属种）。其中富营养属种包括小Reticulofenestra， Reticulofenestra lockeri组，Reticulofenestra bisecta组和Coccolithus pelagicus组，而中等-贫营养属种包括Cyclicargolithus spp.。E*指标与早渐新世营养盐指标具有较强的相关性，但在不同二氧化碳浓度的条件下表现不同的公变趋势。将群落组合与已发表的二氧化碳浓度数据对比，我们提出颗石藻可能在二氧化碳持续降低的环境下改变其对碳源和营养盐的利用方式，指示颗石藻的碳浓缩机制可能开始于早渐新世。 |
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