摘要
终结恐龙时代的白垩纪-古近纪(K-Pg)界线事件发生在6600万年前,由于小行星撞击,地球生态环境发生剧变,导致海洋和陆地生物的大规模灭绝,当时海洋里占据绝对优势地位的初级生产者——颗石藻的灭绝尤为严重.初级生产者是食物链的基础,了解海洋初级生产力在极端环境下的破坏与灾后恢复过程,对于研究当今全球变化下海洋生物碳泵变化及其控制机制具有重要的借鉴意义.本文比较了前人提出的劫难海洋(strangelove ocean)、活跃海洋(living ocean)、弹性海洋(resilient ocean)以及异质海洋(heterogeneous ocean)四个假说,评述每个假说在解释K-Pg事件后海洋生物碳泵如何运行方面的合理性与不足.综合分析全球海盆既有高精度旋回控制、又有表层-深海δ^(13)C垂向梯度的多个站点的数据,以探索K-Pg界线事件后全球海洋生物碳泵效率的变化,指出:(1)K-Pg事件前所有洋盆δ^(13)C垂向梯度与现代海洋一致,这个梯度从陆架到深海有逐渐增加的趋势;(2)K-Pg事件后全球海洋δ^(13)C垂向梯度消失;(3)K-Pg事件后δ^(13)C垂向梯度消失主要是由于海洋表层δ^(13)C突然负偏,其负偏幅度随着从陆架到深海逐渐减小.K-Pg事件后主要初级生产者从较大的颗石藻转变为较小的微型浮游生物,由于真光层中微生物碳泵的作用,更多难降解的惰性溶解有机碳能够下沉到海底,生物碳泵的效率得以维持在一定的水平.微型生物主导的生物碳泵效率不如颗石藻主导的高,但其长期运行能从海洋表层中去除足够的营养盐和有害物质,不仅为更高营养级生物提供食物来源,而且改善K-Pg事件后恶化的海洋物理化学环境,为整个海洋生态系统的恢复和发展铺平道路.关键海洋初级生产者的变换及其控制因素是深时碳循环领域未来需要重点研究的科学问题,而K-Pg事件后生物碳泵表现出的区域或全球变化模式,有助于了解不同海�
The Cretaceous-Paleogene(K-Pg)mass extinction that ended the age of the dinosaurs occurred 66 million years ago,with competing hypotheses including the Deccan Traps volcanic eruption,climate change,and sea level change.However,it is the Chicxulub asteroid impact that has been widely accepted as the most plausible cause.Whatever the reason,the Earth’s ecological environment changed dramatically,leading to a mass extinction of both terrestrial and marine life.Primary producers lie at the base of the food chain and support higher trophic levels,so play an important role in the marine ecosystem.The predominant primary producers in the ocean,coccolithophores(phytoplankton with small Ca CO3 scales covering their cell surface),were among those most severely devastated by the K-Pg mass extinction.So,studying fossil coccolithophores across the K-Pg boundary can provide a better understanding of the destruction and post-event recovery processes of marine primary production(PP)and export production(EP),and the changes and controlling mechanisms of the marine biological carbon pump in the current global climate change.The four hypotheses previously proposed to interpret the post-event primary production,namely strangelove ocean(collapsed PP),living ocean(collapsed EP),resilient ocean(continued PP and EP),and heterogeneous ocean(geography-dependent responses of PP and EP),are illustrated and compared,and their pros and cons reviewed.A dataset is compiled from multiple locations in the global ocean basin including Deep Sea Drilling Program Site 465,Ocean Drilling Program Sites 690,1210,and 1262,and the outcrop at El Kef(Tunisia),with each location having a high-precision cyclostratigraphic time control and an ocean surface-to-deep(bulk carbonate-benthic foraminifera)δ^(13)C vertical gradient.This global dataset is analyzed to explore the changes in the efficiency of global marine biological carbon pump after the K-Pg boundary event.Three important patterns are observed:(1)Prior to the K-Pg event,the verticalδ^(13)C gradien
作者
姜仕军
Shijun Jiang(College of Oceanography,Hohai University,Nanjing 210024,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519080,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2022年第15期1689-1703,共15页
Chinese Science Bulletin
基金
国家自然科学基金(41888101,41976045,41672004)
南方海洋科学与工程广东省实验室(珠海)创新团队建设项目(311021002)资助。
关键词
稳定碳同位素
输出生产力
初级生产者
颗石藻
生物碳泵
白垩纪-古近纪生物大灭绝
stable carbon isotopes
export productivity
primary producer
coccolithophore
biological carbon pump
Cretaceous-Paleogene mass extinction
