Changes of Nitrous Oxide Dynamics Induced by Typhoons: A Case in Zhanjiang Bay, China

Abstract

Under the influence of global climate change, both the frequency and intensity of typhoons are increasing. This study examines the impact of the typhoon on nitrous oxide (N₂O) dynamics in coastal bays, which are the most active areas of N₂O production in the ocean. Employing the ¹⁵N stable isotope labeling technique, coupled with stable isotope mass spectrometry and analysis of key biogeochemical parameters, we conducted a series of five continuous cruises before (one cruise) and after typhoons Chaba (four cruises) in Zhanjiang Bay, a semiclosed coastal bay in the northern South China Sea. Our results showed that the landfall of the typhoon led to a sharp decrease in N₂O concentration in Zhanjiang Bay. However, the typhoon also triggered a substantial production of N₂O in both water column and sedimentary environments, therefore facilitating a rapid recovery of N₂O levels within a short period. In the water column, typhoon-induced enhancement of in situ N₂O production could be attributed to a substantial input of nutrients and terrestrial particles, which creates an anaerobic or hypoxic microenvironment conducive to N₂O production. Concurrently, in the sediment, the deposition of particles derived from typhoon-induced phytoplankton blooms introduces a large amount of fresh particulate organic matter, further promoting N₂O production. Our findings suggest that typhoons are an efficient nitrogen removal process, which has been previously underestimated. By elucidating aspects of the nitrogen cycle in bays during typhoons, this research aids in shaping policies to mitigate greenhouse gas emissions triggered by typhoons.