CDOM Absorption Characteristics with Relation to Fluorescence and Salinity in Coastal Areas of the Southern Baltic Sea

Chromophoric dissolved organic matter (CDOM) absorption measurements and their relationship with fluorescence and salinity are presented for a highly dynamic coastal environment. The results were obtained in the context of seasonal cruises in 1994 in the southern Baltic Sea. They encompass the large gradient of geophysical parameters existing in the environment considered. Comparison of different methods for the normalization of CDOM fluorescence are considered. The method suggested here gives a linear relationship between fluorescence and absorption for the whole data set, where CDOM absorption has a range of 1·4–12·8 m−1with an average of 2·26 m−1at 355 nm. Establishing CDOM absorption and fluorescence relationships is useful because absorption could therefore be inferred from fluorescence measurements which can be acquired more rapidly and with greater sensitivity than absorption. A significant relationship was identified between CDOM absorption and salinity in surface waters. The dependency of these two variables is especially evident in spring during periods of vertical mixing and large input from continental runoff, reflecting the potential of CDOM absorption to be used as a passive tracer of freshwater input. Accurate CDOM absorption measurements are also of use in the definition of remote sensing algorithms and in reflectance and model development and validation.