The fluorescence of dissolved organic matter in the Mid-Atlantic Bight

The fluorescence of dissolved organic matter has been measured on three cruises covering the Mid-Atlantic Bight in the spring of 1994 and 1996 and the summer of 1996. An attempt at a “mass” balance of fluorescent dissolved organic matter (FDOM) on the shelf suggests that more FDOM is present during the spring than during the summer and that deficits during the summer are due to photodegradation. However, subsurface production of FDOM was also prevalent during the summer. These processes were observed due to high shelf productivity and a stable water column that isolates a “cold pool” below sunlit surface waters. Rivers contributed about 10% of the total FDOM to the shelf with the majority of FDOM being advected onto the shelf from slope waters. Net production of FDOM was observed in the spring while net degradation of FDOM was observed in the summer. The fluorescence of dissolved organic matter appears to be a useful measurement for better understanding dissolved organic carbon dynamics as well as ocean optics in ocean margins.