The absorption characteristics of particulate matter in the southern Eastern Indian Ocean

Particulate matter in marine waters plays a crucial role in influencing the light absorption characteristics of seawater. Given the relative scarcity of studies on the absorption characteristics, spatial distribution, and influencing factors of particulate matter in the southern Eastern Indian Ocean, this paper analyzes the spectral characteristics and planar distribution of the particulate matter absorption coefficients in this region. Furthermore, a preliminary analysis of the factors affecting the absorption characteristics of particulate matter in this marine area has been conducted. The results indicate that the total particulate matter absorption spectra in the southern Eastern Indian Ocean consistently display absorption peaks near 440 nm and 675 nm. The absorption contributions from phytoplankton pigments are overwhelmingly predominant. Additionally, the particulate matter in the surface and subsurface layers is more abundant in the summer than in the winter. Regarding the distribution characteristics, the total particulate matter absorption coefficients are higher in the waters east of Sumatra (east of 97°E), while the coefficients are lower in the central deep-sea regions. The absorption characteristics of particulate matter in the southern Eastern Indian Ocean exhibit minimal correlation with changes in sea water temperature, salinity, and phosphate concentration, yet demonstrate a significant correlation with the concentration of chlorophyll-a. This suggests that the particulate matter in these waters predominantly originates from the detritus and colloidal components resulting from the degradation of phytoplankton. Minor fluctuations in the biomass of plankton within the surface and subsurface layers correspondingly induce modifications in the absorption properties of the seawater particulates.