||Marspec East/West Aspect. Using the Surface tools within the Spatial Analyst toolbox in ArcGIS 9.3.1, six geophysical variables were derived from bathymetry to characterize different facets of aspect, slope, and terrain curvature of the seafloor. Aspect, the horizontal orientation of the seafloor, was transformed from circular compass units (i.e., 0º - 360º) into linear vector components ranging from -1 to +1. East/west vector components were defined as +1=due east and -1=due west; north/south vector components were +1 = due north and -1 = due south. Bathymetric slope was measured in degrees ranging from 0º (flat surface) to 90º (vertical slope). Finally, three components of terrain curvature were calculated in order to characterize how ocean bottom currents might interact with the seafloor. Concavity is the second derivative of the bathymetry layer (or the slope of the slope) and represents whether a raster cell is on a hill (negative values) or in a valley (positive values). Plan curvature is the curvature in the direction perpendicular to the maximum slope and indicates whether flow across a surface would diverge (positive values) or converge (negative values). Profile curvature is the curvature in the direction parallel to the maximum slope and indicates whether flow across a surface would accelerate (positive values) or decelerate (negative values).