Hypoxia-Enhanced N2O Production Under Ocean Acidification in the Bohai Sea

• Published in: Frontiers in Marine Science
• Main Authors: Gu, Ting, Jia, Dai, Ma, Xing, Peng, Liying, Zhang, Guicheng, Wei, Yuqiu, Lou, Tingting, Sun, Jun
• Other Authors: National Key Research and Development Program of China, National Natural Science Foundation of China, Changjiang Scholar Program of Chinese Ministry of Education, Tianjin Science and Technology Committee, Tianjin University of Science and Technology
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2021
• Subjects: Ocean Engineering; Water Science and Technology; Aquatic Science; Global and Planetary Change; Oceanography; Ocean acidification
• Online Access: http://dx.doi.org/10.3389/fmars.2021.695105; https://www.frontiersin.org/articles/10.3389/fmars.2021.695105/full

Nitrous oxide (N 2 O) is a powerful greenhouse gas that degrades ozone. Hypoxia and ocean acidification are becoming more intense as a result of climate change. The former stimulates N 2 O emissions, whereas the effects of the latter on N 2 O production vary by the ocean. Hypoxia and ocean acidification may play a critical role in the evolution of future oceanic N 2 O production. However, the interactive effects of hypoxia and ocean acidification on N 2 O production remain unclear. We conducted a research cruise in the Bohai Sea of China to assess the occurrence of ocean acidification in the seasonal oxygen minimum zone of the sea and further conducted laboratory incubation experiments to determine the effects of ocean acidification and hypoxia on N 2 O production. When pH decreased by 0.25, N 2 O production decreased by 50.77 and 72.38%, respectively. In contrast, hypoxia had a positive impact; when dissolved oxygen (DO) decreased to 3.7 and 2.4 mg L −1 , N 2 O production increased by 49.72 and 278.68%, respectively. The incubation experiments demonstrated that the coupling of ocean acidification and hypoxia significantly increased N 2 O production, but, individually, there was an antagonistic relationship between the two. Structural equation modeling showed that the total effects of hypoxia treatment on N 2 O production changes weakened the effects of ocean acidification, with overall positive effects. Generally speaking, our results suggest that N 2 O production from the coastal waters of the Bohai Sea may increase under future climate change scenarios due to increasingly serious ocean acidification and hypoxia working in combination.