Optical properties of colored dissolved organic matter in the Northern Gulf of Mexico

Variations in the concentration and inherent optical properties of colored dissolved organic matter (CDOM) in river-dominated margins provide information on the cycling of carbon and its chemical composition. Large-scale temporal and spatial variability in CDOM concentration and optical properties were observed in the Northern Gulf of Mexico in June of 2000 and April of 2001. Terrestrial CDOM from the Mississippi and Atchafalaya Rivers dominates the region. Although the primary factor controlling CDOM in this region is the quantity of fresh water runoff, strong regional variability in fresh water sources also plays a major role. Physical complexity due to changes in circulation patterns, volume of river flow and multiple river sources makes observation of biological and photochemical effects challenging in this region. We have used two approaches to distinguish between source and transformation effects: mixing models, which include the concentration and inherent optical properties of CDOM from discrete samples, and high-resolution three-dimensional mapping of multi-spectral fluorescence.