Chromophoric dissolved organic matter (CDOM) is the main UV light-absorbing substance in the open ocean (Zepp, 2002 and Kitidis et al., 2006). In spite of the large source of allochthonous CDOM from rivers and coastal wetlands (Blough and Del Vecchio, 2002, Del Vecchio and Blough, 2004b and Spencer et al., 2009), the dominant source of CDOM in the open ocean is thought to be the heterotrophically altered autochthonous material that is produced in and immediately beneath the euphotic zone and also released at depth from sinking particles (Chen and Bada, 1992, Hayase and Shinozuka, 1995, Rochelle-Newall and Fisher, 2002, Nelson et al., 2004, Nelson et al., 2007, Yamashita and Tanoue, 2004 and Swan et al., 2009). CDOM plays an important role in protecting organisms in the upper water column from harmful UV radiation (Williamson et al., 2001 and Zepp, 2002) and represents a significant interference for remote sensing of ocean
Maraviroc (Carder et al., 1989). Further, the products of photochemical degradation of CDOM represent a source of nutrients for phytoplankton (Tarr et al., 2001, Stedmon et al., 2007 and Vähätalo and Järvinen, 2007), metabolic substrates for heterotrophs (Kieber et al., 1989 and Miller et al., 2002), and climatologically relevant gasses (Johannessen and Miller, 2001, Cutter et al., 2004, Stubbins et al., 2006 and Toole et al., 2006). The loss of UV and visible light
absorption and fluorescence that occurs during photochemical degradation of CDOM is referred to as photobleaching (Zika, 1980 and Kieber et al., 1990Chen and Bada, 1992 and Skoog et al., 1996). The basin-scale impact of CDOM photobleaching in surface waters of the remote Pacific Ocean has recently been highlighted by large-scale surveys (Swan et al., 2009 and Yamashita and Tanoue, 2009), which show that CDOM absorbance and fluorescence are strongly depleted in the surface mixed layer.
