Liu Dongyan

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Liu
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Dongyan
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  • Article
    Stable isotopic evidence of nitrogen sources and C4 metabolism driving the world’s largest macroalgal green tides in the Yellow Sea
    (Nature Publishing Group, 2018-11-28) Valiela, Ivan ; Liu, Dongyan ; Lloret, Javier ; Chenoweth, Kelsey ; Hanacek, Daniella
    During recent years, rapid seasonal growth of macroalgae covered extensive areas within the Yellow Sea, developing the world’s most spatially extensive “green tide”. The remarkably fast accumulation of macroalgal biomass is the joint result of high nitrogen supplies in Yellow Sea waters, plus ability of the macroalgae to optionally use C4 photosynthetic pathways that facilitate rapid growth. Stable isotopic evidence shows that the high nitrogen supply is derived from anthropogenic sources, conveyed from watersheds via river discharges, and by direct atmospheric deposition. Wastewater and manures supply about half the nitrogen used by the macroalgae, fertiliser and atmospheric deposition each furnish about a quarter of the nitrogen in macroalgae. The massive green tides affecting the Yellow Sea are likely to increase, with significant current and future environmental and human consequences. Addressing these changing trajectories will demand concerted investment in new basic and applied research as the basis for developing management policies.
  • Article
    Role of C4 carbon fixation in Ulva prolifera, the macroalga responsible for the world's largest green tides
    (Nature Research, 2020-09-07) Liu, Dongyan ; Ma, Qian ; Valiela, Ivan ; Anderson, Donald M. ; Keesing, John K. ; Gao, Kunshan ; Zhen, Yu ; Sun, Xiyan ; Wang, Yujue
    Most marine algae preferentially assimilate CO2 via the Calvin-Benson Cycle (C3) and catalyze HCO3− dehydration via carbonic anhydrase (CA) as a CO2-compensatory mechanism, but certain species utilize the Hatch-Slack Cycle (C4) to enhance photosynthesis. The occurrence and importance of the C4 pathway remains uncertain, however. Here, we demonstrate that carbon fixation in Ulva prolifera, a species responsible for massive green tides, involves a combination of C3 and C4 pathways, and a CA-supported HCO3− mechanism. Analysis of CA and key C3 and C4 enzymes, and subsequent analysis of δ13C photosynthetic products showed that the species assimilates CO2 predominately via the C3 pathway, uses HCO3− via the CA mechanism at low CO2 levels, and takes advantage of high irradiance using the C4 pathway. This active and multi-faceted carbon acquisition strategy is advantageous for the formation of massive blooms, as thick floating mats are subject to intense surface irradiance and CO2 limitation.