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.