Abstract
Vertical profiles of chromophoric dissolved organic matter (CDOM) were determined by absorption coefficient and fluorescence intensity in surface waters (〜300m) at 4 stations of the western North Pacific. Vertical characteristics of CDOM were similar irrespective of differences in oceanic regions, on the one hand, i.e., levels were lower and higher in and below the temporal mixed layer, respectively. CDOM levels, on the other hand, were higher in the subarctic than in the subtropical region throughout the water columns. The ratios of fluorescence intensity to absorption coefficient increased with depth, while, the ratios were within a relatively narrow range in water layers at 4 stations, i.e., the temporal mixed layer (4.11±0.53), beneath the temporal mixed layer to 200m (6.06±1.73) and below (8.33±0.94), irrespective of differences of oceanic regions, indicating that the photochemical characteristics of CDOM in the respective water layers were similar irrespective of differences in oceanic regions. Such distributional characteristics suggested that an integrated effect of the in situ production, and photo- and bio-reactivity of CDOM in the upper water columns might give rise to a different quantity but a similar quality of CDOM among the various oceanic regimes.
