Typhoon stimulates the production of nitrous oxide of water column and sediment in coastal bays

Under the influence of global climate change, both 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 considered the most active areas of N₂O production in the ocean. Employing the ¹⁵N stable isotope labeling technique, coupled with the stable isotope mass spectrometry and analysis of key biogeochemical parameters, we conducted a series of five continuous cruises before and after typhoons in Zhanjiang Bay, a semi-closed coastal bay in the northern South China Sea. Our results showed that the typhoon initially 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 time period. In the water column, typhoon-induced enhancement of in-situ N₂O production may be attributed to a substantial input of nutrients and terrestrial particles, which provide substrates and create anaerobic or hypoxic microenvironments favorable for N₂O production. Concurrently, in the sediment, the deposition of phytoplankton-derived particles following typhoon-induced blooms introduces substantial fresh particulate organic matter, further facilitating N₂O production. Our findings suggest that typhoons represent an efficient, yet transient, nitrogen removal mechanism that has previously been underestimated. By elucidating aspects of the nitrogen cycle in bays, this research aids in shaping policies aimed at mitigating greenhouse gas emissions triggered by typhoons.

受全球气候变化影响，台风的发生频次与强度均呈上升趋势。本研究聚焦台风对海湾海域一氧化二氮（nitrous oxide, N₂O）动态变化的影响——海湾被认为是海洋中N₂O产生最为活跃的区域。本研究采用氮15（¹⁵N）稳定同位素标记技术，结合稳定同位素质谱法（stable isotope mass spectrometry）与关键生物地球化学参数分析，于南海北部半封闭海湾湛江湾开展了台风前后共5次连续航次调查。研究结果显示，台风初期会导致湛江湾海域N₂O浓度急剧下降；但与此同时，台风也会在水体层与沉积环境中触发大量N₂O生成，进而促使N₂O水平在短时间内快速恢复。在水体层中，台风诱导的原位N₂O生成增强，可能源于营养盐与陆源颗粒物的大量输入——这些物质既是N₂O生成的底物，也能形成利于N₂O产生的厌氧或低氧微环境。与此同时，在沉积环境中，台风引发的浮游植物水华后沉降的浮游植物源颗粒物，会带入大量新鲜颗粒态有机质，进一步促进N₂O的生成。本研究结果表明，台风是一种此前被低估的高效但短暂的氮移除机制。本研究通过阐明海湾海域氮循环的相关机制，可为制定减缓台风引发的温室气体排放相关政策提供科学支撑。