A cross-sectional study of lifestyle factors related to body mass index, skeletal muscle mass, and skeletal muscle index in male Japanese workers.

Marine microorganisms play crucial roles in biogeochemical cycling and energy flow in the world's oceans, , . However, global climate change will likely affect future species distributions and ecological functions of these microorganisms. Polar regions are particularly susceptible to the impacts of global warming. For instance, the melting rate of both Arctic and Antarctic sea ice has noticeably accelerated in recent years. This will significantly impact the distribution and function of marine microorganisms in polar seawater. The Antarctic region consists of the Antarctic continent surrounded by the Southern Ocean (SO), serving as a crucial link between the Atlantic, Pacific, and Indian oceans, . Due to its openness and close interaction with adjacent oceans, SO is accompanied by the Antarctic Circumpolar Current (ACC), one of the most violent and intense currents in the world driving the global circulation system. The ACC extends from approximately 35°S to 65°S. It has traditionally been considered to contain five main fronts from north to south: the Subtropical Front (STF), the Subantarctic Front (SAF), the Polar Front (PF), the southern ACC Front (sACCF), and the southern Boundary front (sBdy), separating the subtropical waters from the polar waters. ACC coincides with the belt of westerly wind that is considered as the main driving force forming the ACC. This westerly wind has a strong influence on the transport of heat as well as the biogeographic distribution of airborne bacteria over the SO, . Similarly, the ACC is able to restrict the meridional flow of water and energy in the SO, and together with the circumpolar atmospheric vortex, can mitigate the effects of climate change on Antarctic environments. The ACC has long been considered as a major barrier to the dispersal of the majority of marine eukaryotes in the SO, such as fish and invertebrates. However, as the ACC restricts the movement of heat and water in the SO, how it will shape the geographical distribution of microbes in the SO seawater remains unknown. In this study, we assessed the structure, assembly process, and biogeographic distribution pattern of microbial communities in 45 surface seawater samples collected across the ACC (42°S–70°S). Based on the sampling location and front position, 45 samples were grouped into three regions: the Circum‐Antarctic Region (CAR, 28 selected samples from ZH_02 to ZH_56 distributed on and within the sACCF), the Westerly Wind Region (WWR, 9 samples including ZH_00, ZH_01, and ZH_57 to ZH_63 across all fronts), and the Northern Boundary of Southern Ocean (NBSO, 8 samples from ZH_64 to ZH_71 distributed outside of the STF) (Figure ).