The California Coastal Transition Zone (CTZ) is a region of the North American eastern boundary current system which is associated with cold, nutrient- and pigment- rich filaments that originate near the coast and can extend offshore as much as 300 km. On the basis of recent programs, it is now known that these filaments develop and decay over a period of a few weeks, occur most frequently during the spring and summer (Strub et al., 1991), and are associated with capes and upwelling regions. These filaments are about 50 km wide at peak development and show considerable curvature and meandering. The maximum horizontal velocities within these filaments have been measured in excess of 50 cm s–1 and support a volume transport of 2–6 Sv (1 Sv = 1.0 x 106 m3 s–1). As a result, these features are of considerable interest as they may be an important mechanism for the across-shore flux of carbon and nutrients. Little is known about the relative contribution of carbon export from coastal regions to the open ocean to the overall global carbon cycle.