第六届青年地学论坛

1365 / 2019-08-09 19:01:28

第四纪颗石藻与碳循环

6、海洋地球科学 > 专题4：晚新生代大洋环流与碳循环

Coccolithophore productivity and carbon cycle in Quaternary: Through the distinct ecological preferences of the lower photic Florisphaera profunda and upper photic Noëlaerhabdaceae family, we reconstructed the Noëlaerhabdaceae coccolithophore productivity over Quaternary in the South China Sea, with nearly neglectable signals of regional orbital climatic forcing, thus reflecting a long term evolutionary trend in response to major carbon cycle changes. Before 1.6 Ma, coccolithophore productivity exhibited a gradually decreased trend, indicating that their growth was depressed by the declination of atmospheric CO2 since the late Pliocene, like other C3 photosynthetic pathway plants. Hence, taking bicarbonate ions as the major carbon sources for photosynthesis can be an effective way to cope with CO2 limitation, however in the expense of lowering calcification. This possibly explains the co-evolution of coccolith size and atmospheric CO2 in Cenozoic. After 1.6 Ma, coccolithophore productivity showed major rebounds due to the enhanced oceanic bicarbonate availability that could be resulted from the enhanced weathering input and amplification of eustatic sea level changes. Three remarkable coccolithophore productivity spikes were following the major carbon reservoir changes at approximate 0.5 Ma, 1.0 Ma, and 1.55 Ma, respectively. The ocean carbon cycle changes can be related to the re-organization of ocean circulations, that is, the northward invasion of Antarctic Bottom Water with excess CO2, causing a long-term carbonate dissolution cycle and thus, providing the essential bicarbonate ions for coccolithophore growth globally.