Marine dissolved organic carbon (DOC) is one of the largest and most dynamicpools of reduced carbon on earth. Photochemical processes have the potential tosignificantly affect the content of this DOC pool. Photochemical oxidation to carbonmonoxide and carbon dioxide are two direct pathways for the removal of DOC from themarine system. Indirectly, photochemical processes can lead to the removal of DOCthrough the alteration of chemical structures rendering them more biologically labile. Inorder to assess the influence of photochemistry on the coastal carbon cycle the variabilityof these processes must be well constrained. To calculate photochemical production inmarine waters, it is crucial to know how light is absorbed by chromophoric dissolvedorganic matter (CDOM), as well as the spectral efficiency of the resulting photochemicalreactions (i.e. the apparent quantum yield (AQY) spectra).The challenges of using visible wavelength CDOM absorption data to modelultraviolet absorption data are investigated. Direct measurements of ultravioletabsorption data model photochemical processes best. When this is not possible, visibledata can be used with an accuracy of +/- 10% in coastal waters. Either a hyperbolicabsorption model or one using correction factors applied to a traditional exponentialmodel will allow for similar accuracy in the ultraviolet portion of the absorptionspectrum.The variability of photochemical oxidation of dissolved organic carbon in acoastal system was studied in order to constrain remote sensing calculations. Thevariability of CO and CO2 AQY spectra were relatively well constrained in threeestuaries of Georgia, USA. The AQY for CO varied within +/- 12.7% year-round whileCO2 varied within +/- 33.6% year-round. Hyperspectral remote sensing reveals finescalehydrodynamic structure in estuarine systems and is readily adaptable tophotochemical modeling applications.Defining the variability of photochemistrys influence on the biological lability ofDOC is a complex undertaking. Unlike direct photochemical oxidation of DOC to COand CO2, the biologically labile products (BLPs) of incomplete oxidation can themselvesbe photochemically reactive. Competition between production and destruction of BLPsduring irradiation is a significant consideration when determining the quantitativeinfluence of photochemistry on marine systems.