BIOLOGICAL STRUCTURE AND

The Japan/East Sea (JES) contains several oceanic regions separated by dynamic boundaries. These distinct regions, and the physical features that establish and maintain the boundaries between the regions, have signifi cant impacts on its ocean biology. Until recently, most studies of the biology of the JES have focused on nearshore regions, with few detailed studies of the interior of the JES or the dynamic features that defi ne the different regions. In addition, the classic sampling methods used in previous work have not allowed high-resolution studies of biological-physical interactions associated with key dynamic mesoscale frontal zones, quasi-synoptic surveys of water column and bio-logical structure in three dimensions, or broad-scale description of the seasonal cycles in the different biogeographic regions of the JES. A UNIQUE BASIN The central basin of the JES contains two primary biogeographic regions, defi ned by the dominant currents and hydrographic structures (Figures 1 and 2). The region is bisected by the dramatic the Subpolar Front (SPF) and its associated mesoscale circulation. The SPF persists between the cold water in the north and the warmer subtropical water in the south and fl ows from west to east from the Korean Peninsula to Tsugaru Strait (e.g., Isoda et al., 1991