My research is driven by my curiosity and interests in a series of scientific questions. How sedimentary environments and oceanographic conditions changed in coasts and oceans response to climate change in the past? How much difference the changes between coasts and oceans? What are the influence factors on the changes and differences? How the climatic and sea-level changes as well as human activity affect coastal environments and ecosystems, especially marine primary productivity (PP)? Seeking answers to these questions inspires me to work on reconstructions of paleoceanographic conditions on various time and spatial scales using multiple proxies. I mostly use palynological analysis (microfossils of dinoflagellate cysts, pollen and spores, charcoal, foraminiferal organic linings, etc.), sediment facies analysis (grain-size, structure, color, fossil contents, sedimentary sequences, etc.) and geochemical proxies (Si, TOC, Ba, Fe, Cr etc.) to reconstruct past climate (e.g. temperature and precipitation), oceanographic conditions (e.g., SST, SSS, marine PP, eutrophication level and oxygenation), sea-level change, and human activities. Dinoflagellate cysts are used for the reconstruction of specific oceanographic patterns. Pollen and spores in marine environment could reflect regional vegetation, climate, or coastal vegetation and coastline migration. Geophysical survey, sediment facies and geochemical analyses help for understanding regional background of sedimentary environments. With these interests and methods, my research focuses on and contributes to the following aspects in the Pacific Ocean with large human population living in coastal areas and serious coastal risks from sea-level rise, climate warming, and eutrophication.
a. Reconstruction of oceanographic conditions in the North Pacific at various time scales
My current research is focused on understanding paleoceanographic conditions and the impacts of climate and sea-level change on marine PP during the late Quaternary. My Ph.D. research showed, for the first time, that marine dinoflagellate cysts from the South China Sea reflected not only the regional EAM climatic change, but also the impacts from relative sea-level change in the western Pacific. This work contributed to developing terrestrial and marine palynological indicators of winter or summer monsoon signals as well as oceanographic environments of the South China Sea (SCS). The high-resolution reconstructions of Holocene East Asian Monsoon (EAM) climate and oceanographic condition of the northern SCS provided insights into regional climate events in the western low-latitude Pacific Ocean and their impacts on local oceanography and ecology. Specifically, it identified that Holocene relative sea-level changes show different trends between the western and the eastern high-latitude Pacific due to complex eustatic and isostatic interactions. My postdoctoral research is answering questions: How did PP on the west Vancouver Island margin respond to the Holocene climatic and hydrographic changes? This work aims to use marine microfossils and Cr isotopes to: (i) quantitatively reconstruct marine PP, sea-surface temperature and sea-surface salinity in the northeast Pacific during the Holocene; (ii) reconstruct regional climate changes and their impacts on the PP and other oceanographic conditions.
b. Asian monsoon climatic and oceanographic changes in the western Pacific region during the Holocene
East Asian monsoon (EAM) results in differential land–sea heating between the Western Pacific Warm Pool and the Asian continent associated with seasonal changes in wind direction, precipitation and river runoff. Palynological distribution in marine or coastal sediments are not only influenced by climatic change, but also are controlled by sediment environment evolutions. Based on pollen data and sediment facies analyses of cores from the northern South China Sea, Beibu Gulf, Changjiang Delta, Songhong (Red River) Delta and the east coast of South Korea during the Holocene, EAM climate in millennium-centennial time scales in the Western Pacific region were reconstructed. The rapid rise of sea level resulted in the opening of Taiwan and Qiongzhou Straits in the early Holocene, forming the present oceanographic patterns in the mid-Holocene. For the first time, the mid-Holocene Optimum was observed at the centennial scale and three strengthened winter monsoon intervals were reconstructed. This research filled up the resolution gap between the annual-decade and glacial-interglacial scales on the monsoon climate in Asian regions. This research filled up the resolution gap between the annual-decade and glacial-interglacial scales on the monsoon climate in the Asian Pacific region.
c. Holocene mangrove succession and mega-delta initiation in response to the relative sea-level change and monsoon climatic variation.
Mangrove forest, growing in the subtropical and tropical tidal zones, is sensitive to the coastal environmental conditions, such as salinity and temperature. Sea-level change strongly affected the coastal mangrove system during the Holocene. Using mangrove pollen and chemical biomarkers, we reconstructed the history of the mid-Holocene mangrove succession in the Mekong Delta region and the late-Holocene relative sea-level changes along the northern coast of the South China Sea. We also predicted the evolution of mangrove communities in the scenario of sea-level rising and inner dam building. Using mangrove pollen and plant macrofossils, I also provided strong evidence that Asian mega-deltas were initiated when the rate of sea-level rise declined in the mid-Holocene. Mangrove pollen from the Mekong Delta in Vietnam and the Krishna Delta in India, and pollen assemblages of marsh plants from the Changjiang Delta in China and the Mississippi Delta in the United States provided details on how coastal vegetation and delta initiation/development responded to the relative sea-level change and the regional climate changes in various regions.
d. Human activities in response to modern mega-delta initiation and coastal development.
The Holocene climate change, sea-level rise, as well as delta initiation and development, have influenced the establishment and development of agriculture on delta plains. With the delta development, rice exploitation also extended seaward reflected by archaeological records. Along the coast of South China, reclamation of mangrove swamps for farmland resulted in mangrove degradation rather than climate change. In addition, fire has played an essential role in human activities. Most of previous research proposed that frequent-fire regimes in the late Holocene were associated with intensified agriculture development. Using palynomorphs, our work found intensified-fire regime periods in the Red River delta regions were strongly associated with warfare and unrest.
Paleobiology, Palynology, Marine sedimentology, Introductory Geology, Palaeoclimatology, Environmental Archaeology, and a seminar lecture of Global Climate Change and Challenges to Coastal Regions.
B.Eng. Chang'an University (Xi'an Geology College), China (1994)
M.Sc. Tongji Univeristy, China (1997)
Ph.D. University of Victoria (2018)
Posdoctoral Fellow, University of British Columbia (2019-2020)
Nageswara Rao, K., Saito, Y., Naga Kumar, K.Ch.V., Kubo, S., Pandey, S., Li, Z., Demudu, G., Rajawat, A.S., 2020. Holocene evolution and Anthropocene destruction of the Krishna Delta on the east coast of India: Delta lobe shifts, human impacts, and sea-level history. Marine Geology (online). https://doi.org/10.1016/j.margeo.2020.106229.
Li, Z., Pospelova, V., Kawamura, H., Luo, C., Mertens, N.K., Hernandez-Almeida, I., Yin, K., Wu, Y., Wu, H., Xiang, R., 2019. Dinoflagellate cyst distribution in surface sediments from the South China Sea in relation to hydrographic conditions and primary productivity. Marine Micropaleontology (on line). https://doi.org/10.1016/j.marmicro.2019.101815.
Mertens, K.N., Gu, H., Gurdebeke, P.R., Takano, Y., Clarke, D., Aydin, H., Li, Z., Pospelova, V., Matsuoka, K., Head, M.J., 2019. A review of rare or not well-known extant marine organic-walled dinoflagellate cyst taxa of the orders Gymnodiniales and Peridiniales from the Northern Hemisphere. Marine Micropaleontology (online). https://doi.org/10.1016/j.marmicro.2019.101 773.
Gurdebeke, P.R., Mertens, K.N., Pospelova, V., Matsuoka, K., Li, Z., Gribble, K.E., Gu, H., Bogus, K., Vrielinck, H., Louwye, S., 2019. Taxonomic revision, phylogeny, and cyst wall composition of the dinoflagellate cyst genus Votadinium Reid (Dinophyceae, Peridiniales, Protoperidiniaceae) Palynology (online). https://doi.org/10.1080/01916122.2019.1580627.
Li, Z., Pospelova, V., Lin, H.-L., Liu, L., Song, B., 2018. Seasonal dinoflagellate cyst production and terrestrial palynomorth deposition in the monsoon influenced South China Sea: A sediment trap study from the Southwest Taiwan waters. Review of Palaeobotany and Palynology 257, 117–139. https://doi.org/10.1016/j.revpalbo.2018.07.007
Song, B., Yi, S., Jia, H., Nahm, W.H., Kim, J.C., Lim, J., Lee, J.Y., Sha, L., Mao, L., Yang, Z., Nakanishi, T., Hong, W., Li, Z., 2018. Pollen record of the mid- to late-Holocene centennial climate change on the east coast of South Korea and its influential factors. Journal of Asian Earth Science 115, 240–249. https://doi.org/10.1016/j.jseaes.2017.11.006
Li, Z., Pospelova, V., Liu, L., Zhou, R., Song, B., 2017. High-resolution palynological record of Holocene climatic and oceanographic changes in the northern South China Sea. Palaeogeography, Palaeoclimatology, Palaeoecology 483, 94–124. https://doi.org/10.1016/j.palaeo.2017.03.009
Meng, X., Xia, P., Li, Z., Meng, D., 2017. Mangrove development and its response to Asian Monsoon in the Yingluo Bay (SW China) over the last 2000 years. Estuaries and Coasts 40, 540–552. https://link.springer.com/10.1007/s12237-016-0156-3
Song, B., Li, Z., Lu, H., Mao, L., Saito, Y., Yi, S., Lim, J., Li, Z., Lu, A., Sha, L., Zhou, R., Zuo, X., and Pospelova, V., 2017. Pollen record of the centennial climate changes during 9–7 cal ka BP in the Changjiang (Yangtze) River Delta plain, China. Quaternary Research 87, 275–287. https://doi.org/10.1017/qua.2017.1
Zuo, X., Lu, H., Li, Z., Song, B., Xu, D., Zou, Y., Wang, C., Huan, X., He, K., 2016. Phytolith and diatom evidence for rice exploitation and environmental changes during the early mid-Holocene in the Yangtze Delta. Quaternary Research 86, 304–315. https://doi.org/10.1016/j.yqres.2016.08.001
Meng, X., Xia, P., Li, Z., Meng, D., 2016. Mangrove degradation and response to anthropogenic disturbance in Maowei Sea (SW China) since 1926 AD: Mangrove-derived OM and pollen. Organic Geochemistry 98, 166–175. https://doi.org/10.1016/j.orggeochem.2016.06.001
Nguyen, T.T.H., Zhang, W., Li, Z., Li, J., Ge, C., Liu, J., Bai, X., Feng, H., Yu, L., 2016. Assessment of heavy metal pollution in Red River surface sediments, Vietnam. Marine Pollution Bulletin 113, 513–519. https://doi.org/10.1016/j.marpolbul.2016.08.030
Nguyen, T.T.H., Zhang, W., Li, Z., Li, J., Ge, C., Liu, J., Bai, X., Feng, H., Yu, L., 2016. Magnetic properties of sediments of the Red River: Effect of sorting on the source-to-sink pathway and its implications for environmental reconstruction. Geochemistry, Geophysics, Geosystems 17, 270–281. https://doi.org/10.1002/2015GC006089
Nageswara Rao, K., Saito, Y., NagaKumar, K.Ch.V., Demudu, G., Rajawat, A.S., Kubo, S., Li, Z., 2015. Palaeogeography and evolution of the Godavari delta, east coast of India during the Holocene: An example of wave-dominated and fan-delta settings. Palaeogeography‚ Palaeoclimatology‚ Palaeoecology 440, 213–233. https://doi.org/10.1016/j.palaeo.2015.09.006
Xia, P., Meng, X., Li, Z., Feng, A., Yin, P., Zhang, Y., 2015. Mangrove development and its response to environmental change in Yingluo Bay (SW China) during the last 150 years: Stable carbon isotopes and mangrove pollen. Organic Geochemistry 85, 32–41. https://doi.org/10.1016/j.orggeochem.2015.04.003
Song, B., Li, Z., Saito, Y., Okuno, J., Li, Z., Lu, A., Hua, D., Li, J., Li, Y., Nakashima, R., 2013. Initiation of the Changjiang (Yangtze) delta and its response to the mid-Holocene sea level change. Palaeogeography‚ Palaeoclimatology‚ Palaeoecology 388, 81–97. https://doi.org/10.1016/j.palaeo.2013.07.026
Li, Z., Saito, Y., Li, Z., Tamura, T., Song, B., Lu, A., Sieng, S., Li, J., Zhang, Y., 2012. Mid-Holocene mangrove succession and its response to sea level change in the upper Mekong delta, Cambodia. Quaternary Research 78, 386–399. https://doi.org/10.1016/j.yqres.2012.07.001
Mao, L., Batten, D.J., Fujiki, T., Li, Z., Dai, L., Weng, C., 2012. Key to the mangrove pollen and spores of the southern China: an aid to palynological interpretation on Quaternary marine deposits in the South China Sea. Review of Palaeobotany and Palynology. 176–177: 41–67. https://doi.org/10.1016/j.revpalbo.2012.03.004
Li, Z., Zhang, Y., Li, Y., Zhao, J., 2010. Palynological records of Holocene monsoon change from the Gulf of Tonkin (Beibuwan)‚ northwestern of South China Sea. Quaternary Research. 74: 8–14. https://doi.org/10.1016/j.yqres.2010.04.012
Li, Z.‚ Saito, Y., Dang, X.‚ Matsumoto‚ E., Vu, Q., 2009. Warfare rather than agriculture as a critical influence on fires in the late Holocene‚ inferred from northern Vietnam. Proceedings of the National Academy of Sciences of the United States of America (PNAS). 106 (28): 11472–11477. https://www.pnas.org/content/pnas/106/28/11490.full.pdf
Li, Z., Zhang, Z.‚ Li, J., Li, Z., Liu, L., Fan, H., Li, G., 2008. Pollen distribution in surface sediments of a mangrove system‚ Yingluo Bay, Guangxi‚ China. Review of Palaeobotany and Palynology. 152: 21–31. https://doi.org/10.1016/j.revpalbo.2008.04.001
Li, Z., Saito, Y., Matsumoto‚ E., Wang, Y., Tanabe‚ S., Zang, J., Vu, Q., 2006. Climate change and human impact on the Song Hong (Red River) delta‚ Vietnam‚ during the Holocene. Quaternary International. 144: 4–28. https://doi.org/10.1016/j.quaint.2005.05.008
Li, Z., Saito‚ Y., Matsumoto‚ E., Wang, Y., Tanabe, S., Vu, Q., 2006. Palynological Record of climate change during the last deglaciation from the Song Hong (Red River) delta‚ Vietnam. Palaeogeography‚ Palaeoclimatology‚ Palaeoecology. 235: 406–430. https://doi.org/10.1016/j.palaeo.2005.11.023