Light absorption characteristics of chromophoric dissolved organic matter (CDOM) in the coastal waters of northern Bay of Bengal during winter season

Abstract

Absorption spectra of chromophoric dissolved organic matter (CDOM) and other physico-chemical components were measured in the coastal water of northern Bay of Bengal (nBoB) lying adjacent to West Bengal coast, India, during October, 2014-March, 2015. Absorption coefficient [a_CDOM(440)] of CDOM exhibited a considerable inverse linear relationship with salinity in the surface waters implying traditional mixing effect of marine and fresh water. A dominant terrestrial CDOM signal influenced by higher fresh water discharge from the river Hugli was seen prior of winter (October, 2014). However, during January, a_CDOM(440) value again increased along with a concomitant increase in chlorophyll-<i>a</i>. However, total suspended matter (TSM) showed strong linear positive and consistent relationship with a_CDOM(440) throughout the study period, ascertaining terrestrial source of CDOM. Moreover, prior of winter, study site receives more discharge from rivers with corresponding signals of lower slope value indicating less aged and high molecular weight of CDOM.