Organic matter (OM) is a critical factor which regulates nitrogen loss pathways of denitrification and anammox for microbes in marine ecosystems. However, only a little attention has been paid to contrasting studies on denitrification and anammox in sandy and muddy sediments, especially in the coastal continental shelf dominated by sandy sediments.
Recently, the research team led by Prof. SONG Jinming from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) revealed the impact of OM on the nitrogen loss rate of muddy and sandy sediments in the East China Sea (ECS) coastal shelf, and obtained a new understanding of the pathways and mechanisms of sediment nitrogen loss.
The study was published in Science of The Total Environment on Sept. 14.
In this study, researchers analyzed the interaction between nitrogen loss and OM at the molecular level. It was found that organic-rich muddy sediments obtained higher nitrogen loss relative to sandy sediments. In muddy sediments, anammox-specific biomarkers of ladderane lipids were significantly greater than in sandy sediments. Simultaneously, the increase of total organic carbon (TOC) content enchanted the abundance of anammox functional gene hzsB (subunit B-containing hydrazine synthase) and denitrification functional gene nosZ (nitrous oxide reductase). Furthermore, the anammox rate and the denitrification rate were positively correlated, indicating a coupled relationship between denitrification and anammox. OM in sediments can serve as a carbon source for heterotrophic denitrifying nitrogen loss, and its decomposition provides substrates for autotrophic anammox reactions.
"Conducting research on denitrification and anammox in muddy and sandy sediments can effectively reveal the crucial environmental factors that control the loss of nitrogen in coastal areas and their impact mechanisms, and provide essential empirical support for maintaining the health of offshore ecological environment," said LAI Xiaoshuang, first author of the study.
"This study is the first to combine the biomarkers ladderane lipids with microbial functional genes to elucidate the nitrogen removal rate of muddy and sandy sediments, providing a rare means to more effectively understand and predict the nitrogen cycle of sediments in coastal marine ecosystems," said Prof. SONG.
This study was supported by the Marine S&T Fund of Shandong Province for the Pilot National Laboratory for Marine Science and Technology (Qingdao), National Natural Science Foundation of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, and Natural Science Foundation of Shandong Province.
Fig. 1 Spatial distribution of denitrification and anammox genes abundance in the ECS coastal shelf.
Fig. 2 Pearson correlation analysis between environmental factors and functional genes of denitrification and anammox in surface sediments of the ECS coastal shelf.
Lai, X.S., Li, X.G*., Song, J.M*., Yuan, H.M., Duan, L.Q., Li, N., Wang, Y.X., 2023. Nitrogen Loss from the Coastal Shelf of the East China Sea: Implications of the Organic Matter. Sci. Total Environ. 854, 158805.
(Text by LAI Xiaoshuang)
Media Contact:
ZHANG Yiyi
Institute of Oceanology
E-mail: zhangyiyi@qdio.ac.cn
(Editor: ZHANG Yiyi)