Typhoon-induced vertical mixing rapidly reshapes bacterioplankton communities across ocean depths

A research cruise investigating marine bacterioplankton communities and associated biogeochemical processes was conducted aboard the R/V Ocean Researcher I in the southern East China Sea from July 6 to July 17, 2018. While the passage of Typhoon Maria (July 9-11) interrupted our sampling, it provided a rare opportunity to assess the typhoon's impacts by comparing pre-typhoon (July 6-8) and post-typhoon (July 13-16) ecosystem conditions. During both the pre- and post-typhoon sampling periods, seawater samples were collected from eight stations, with four distinct water layers sampled at each station: the surface layer, the deep chlorophyll maximum layer, the bottom layer, and a middle layer positioned at the midpoint between the DCM and the BOT. The depth of the DCM was determined in real time using fluorescence profiles from the onboard Conductivity-Temperature-Depth (CTD) sensor (Seabird SBE 911plus). Notably, at Station 3 post-typhoon, there was no separation between the SUR and the DCM, as both occurred at about 6 m depth. Additionally, at Station 5 post-typhoon, the DCM and the BOT were separated by less than 30 m, and thus the MID sampling was omitted. Consequently, the MID samples from Station 5 were excluded from further analysis.