Seasonal variation of CDOM in the Middle Atlantic Bight: terrestrial inputs and photooxidation

Abstract

Surveys of the fluorescence and absorption of chromophore-containing dissolved organic matter (CDOM) were made along a cruise line extending from the mouth of Delaware Bay southeast to the Sargasso Sea. With shallow stratification in August, photobleaching dramatically altered the optical properties ofthe surface waters, with ~70% ofthe CDOM absorption and fluorescence lost through photooxidation in the waters at the outer shelf. S, the slope ofthe log-linearized absorption spectrum of CDOM, increased offshore and appeared to increase with photodegradation. The increase in S underscores the difficulty in developing ocean color algorithms to predict Chl concentrations in highly absorbing coastal waters. The seasonal variation in the CDOM fluorescence-absorption relationship and fluorescence quantum yields was less than 15%, making the airborne lidar approach for remote determination of CDOM absorption coefficients a robust technique. The photooxidation of CDOM in August also affected the relationship between CDOM and DOC, which can be described by a simple model.