Spatial and temporal variability of colored dissolved organic matter absorption properties in the Taiwan Strait

Abstract

Spatial and temporal variability of the absorption properties of colored dissolved organic matter (CDOM) in the Taiwan Strait was investigated in summer (July to August of 2006) and winter (from December 2006 to January of 2007) seasons. The CDOM absorption coefficient at 280 nm (a (280)) showed a decreasing trend from nearshore to offshore areas while the spectral slope coefficient parameter calculated between wavelengths 275-295 nm (S (275-295)) showed an increase, indicative of decreasing aromaticity and molecular weight of the CDOM. The average a (280) in winter (1.47 +/- 0.50 m(-1)) was significantly higher than in summer (1.10 +/- 0.41 m(-1)), while the average S (275-295) in winter (26.7 +/- 5.2 A mu m(-1)) was significantly lower than in summer (30.6 +/- 5.5 A mu m(-1)), demonstrating clear seasonal variation in CDOM abundance and properties in the Taiwan Strait. A three-endmember conservative mixing model showed that local terrestrial CDOM inputs from several rivers along the western coast were small (< 5%). However, the distribution of CDOM in the Taiwan Strait is mainly controlled by water mass movement [i.e., the Zhe-min Coastal Current (ZCC) and the Kuroshio Branch Current (KBC) in winter and the South China Sea Water (SCSW) in summer]. Biological activity was also an important factor affecting the distribution of CDOM in the offshore region in summer months.