不同营养盐水体甲烷产生机制与潜力对比

甲烷是重要的温室气体，近海河口海域是甲烷产生和释放的活跃区域。于2021年对富营养化的九龙江河口（6月）和贫营养化的陆丰近海（8月）表层水进行了受控培养实验。结果显示，在添加碳氮以及甲基膦酸的陆丰近海海水样品中，观测到甲烷浓度增加了两个数量级，说明陆丰近海可能存在依赖甲基膦酸路径的甲烷生产。九龙江河口水体也存在基于甲基膦酸、二甲基巯基丙酸内盐和三甲胺路径生产甲烷的过程，其中以甲基膦酸路径产生的甲烷最多（增长率211.0%）。对比同样条件下的甲基膦酸-甲烷产生实验，陆丰近海水体产生的甲烷约是九龙江河口的22倍，表明贫营养化水体更加有利于基于甲基膦酸路径的甲烷产生。

Comparison of mechanism and potential production of methane in different nutrient seawaters

Methane is an important greenhouse gas, which is produced and released actively in estuaries and coastal seas. In 2021, we conducted incubation experiments in the oligotrophic waters of Lufeng offshore (August) and the eutrophic waters of Jiulongjiang Estuary (June) to study the potential production of methane. As shown from the results, methane concentration increased by two orders after addition of carbon, nitrogen and methylphosphonate, suggesting the presence of methylphosphonate-dependent methane production in Lufeng offshore. The methylphosphonate, dimethylsulphoniopropionate and trimethylamine-based methane productions were also found in Jiulongjiang Estuary, with the highest methane-increased rate (211.0%) in the methylphosphonate group. Comparing the experiments conducted in the two study sites with same amount of methylphosphonate addition, we found that produced-methane was 22 times in Lufeng offshore as high as in Jiulongjiang Estuary, indicating that the poor-nutrient water may facilitate the methylphosphonate-based methane production.