Integrated effects of Ulva prolifera bloom and decay on nutrients inventory and cycling in marginal sea of China

Pengyan Zhang; Yu Xin; Xiaosong Zhong; Zhenwei Yan; Yuemei Jin; Maojun Yan; Tao Liu

doi:10.1016/j.chemosphere.2020.128389

Integrated effects of Ulva prolifera bloom and decay on nutrients inventory and cycling in marginal sea of China

Chemosphere. 2021 Feb;264(Pt 1):128389. doi: 10.1016/j.chemosphere.2020.128389. Epub 2020 Sep 25.

Authors

Pengyan Zhang¹, Yu Xin², Xiaosong Zhong³, Zhenwei Yan⁴, Yuemei Jin⁵, Maojun Yan⁶, Tao Liu⁷

Affiliations

¹ College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266005, China. Electronic address: zhangpengyan@ouc.edu.cn.
² Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, 266100, China. Electronic address: xinyu312@ouc.edu.cn.
³ Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, 266100, China. Electronic address: zxs@stu.ouc.edu.cn.
⁴ Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, 266100, China. Electronic address: 21190311007@stu.ouc.edu.cn.
⁵ College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266005, China. Electronic address: mgbl_sr@ouc.edu.cn.
⁶ Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, 266100, China. Electronic address: yanmaojun@sjtu.edu.cn.
⁷ College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266005, China; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000, China. Electronic address: liutao@ouoc.edu.cn.

PMID: 33038757
DOI: 10.1016/j.chemosphere.2020.128389

Abstract

Ulva prolifera blooms occur annually in the Yellow Sea. Most studies focus on how U. prolifera blooming is influenced by nitrogen chemical forms and concentrations, while little concern goes to how U. prolifera bloom-decay cycle would impact local seawater nutrients structure. Therefore, we use ¹⁵N-labeled NO₃ tracers and transcriptome analysis to determine N uptake, metabolism, and interconversion during U. prolifera growth and decay, so that we can quantify the conversions rate and fluxes of different nitrogen chemical forms. U. prolifera absorbes 17.37 μmol g^-1·d^-1 NO₃-N during growth. NO₃-N predominates (73.75-92.15%) in the dissolved inorganic nitrogen (DIN) in U. prolifera. During decay, NH₄-N accountes for 60.87-92.13% of the in-cell DIN. The decomposing U. prolifera releases considerable amounts of NH₄-N and dissolved organic nitrogen (DON) (63.8-98.2% < 1 kDa fraction and 1.8-36.2% is > 1 kDa fraction) into the ambient environment. The high DON release rate (59.57 μmol g^-1 d^-1) indicates active DON biosynthesis in U. prolifera. The isotope ¹⁵NO₃-N tracer showes that 73.6% of the ¹⁵NO₃-N is transformed to DON. The <1 kDa and the >1 kDa fractions account for 67.46-90.86% and 9.14-32.54% of the DON, respectively. The high efficiency of U. prolifera in utilizing NO₃-N is explained by the responsive nitrate/nitrite transporter in cell membrane, and the DON biosynthesized capability is attributed to the up-regulated glutamine synthetase. Our study highlights the unique role of U. prolifera as a "Nitrogen-Pump" in converting nitrogen chemical forms during its bloom-decay cycle and quantifies its impacts on local N-nutrients inventory.

Keywords: Decay; Dissolved inorganic nitrogen; Dissolved organic nitrogen; Nitrogen isotope; Tangential flow filtration; Ulva prolifera.

MeSH terms

China
Eutrophication
Nitrogen
Nutrients
Ulva*

Substances

Nitrogen