Estimation of N and N₂O cycling processes using the information of bacterial functional genes in the East Sea

Marine nitrogen (N) cycle plays important roles in controlling marine ecosystem and biogeochemistry, as it is well known as a limiting element for marine productivity and significantly influences on the carbon and phosphorus cycles in the marine environment. Also, nitrous oxide (N₂O) production via marine N cycling is regarding as climate interaction with a big concern owing to its significant warming potential in the atmosphere. The East Sea (ES) is a semi-enclosed marginal sea, but frequently referred to as a miniature ocean as it shows multiple ocean dynamic processes. Recently, a number of studies reported that the ES is rapidly changing due to anthropogenic perturbations. Given that understanding of the ES’s biogeochemical cycles under such a condition is apparently urgent, we have little knowledge about particularly N cycling and N₂O production mechanisms to date. At present, the application of metagenomics approaches is widely used for understanding marine N cycle as an important means. Here, using the information of bacterial functional genes, we for the first time investigate (1) N cycling processes and (2) N2O production pathways during June and October 2021 at three different depths (0m, 150m, and 750m) of the ES.