Human activities have caused a large amount of reactive nitrogen (N) to enter coastal and marine ecosystems, which changes N biogeochemical cycling and leads to a series of ecological problems in coastal areas such as eutrophication, hypoxic zone expansion, algal blooms and the increase in greenhouse gas emissions. Coastal sediments are vital for the removal of N from marine ecosystems. However, what factors control the regional-scale sedimentary N removal process is scarcely known.   

Recently, a research team led by Wang Chao from the Institute of Applied Ecology, Chinese Academy of Sciences (CAS) collected sediment samples along a 2500 km coast of China. And they determined factors affecting the process and rates of N removal by using stable N isotope labeling methods and molecular biology techniques.  

The researchers found that denitrification was the most critical process controlling the N removal from the coastal sediments, which accounted for roughly 90% of the total removal of nitrogen.  

The denitrification process in sediments was directly associated with bacterial diversity and microbial functional gene abundance, and it was indirectly affected by abiotic factors such as temperature, oxygen content and soluble organic carbon concentration.  

According to the researchers, the annual flux of sedimentary denitrification in the coastal areas alongside the Bohai Sea, the Yellow Sea, the East China Sea and the South China Sea is estimated to be 9.2 Tg N year^-1, approximately accounting for 4% of the global ocean denitrification rate.   

These findings are of great significance for deepening understanding of N cycles in the marine offshore ecosystems.  

The study titled "Biotic and abiotic controls on dinitrogen production in coastal sediments"), published in Global Biogeochemical Cycles, was supported by the CAS Key Research Program for Frontier Sciences and the Youth Promotion Association of CAS. 

Contact 

YUE Qian 

Institute of Applied Ecology, Chinese Academy of Sciences 

Tel: 86-24-83970324 

E-mail: yueqian@iae.ac.cn 

Web: http://english.iae.cas.cn