<正>Planktonic archaea are among the most abundant members of marine microbes and play a crucial role in driving biogeochemical cycles. It is now recognized that there are four major phylogenetic groups of planktonic archaea(Marine Group I–IV, MGI–IV), which include the chemoautotrophic ammonia-oxidizing Thaumarchaeota(MGI), as well as the heterotrophic Euryarchaeota(MGII and MGIII) and Haloarchaea-affiliated archaea(MGIV) [1]. The MGII Euryarchaeota, the most predominant planktonic heterotrophic archaea in ocean waters, exhibit a global distribution and can at times account for over 30% of the marine microbial community across at least seventeen candidate genera [1,2]. Previous studies have indicated that the distribution of MGII often coincides with that of phytoplankton because they tend to degrade phytoplankton-derived organic carbon, playing a significant role in the cycling of organic carbon in the ocean [3].