[M-SD41] Geospatial applications for natural resources, environment and agriculture

[MSD41-P08] Vertical diffuse attenuation coefficient and euphotic zone depth of the Mahakam Delta coastal waters, Indonesia

*SYARIF BUDHIMAN^1,2, Ety Parwati¹, Pingkan Mayestika Afgatiani¹, Djoko Triyono², A Harsono Soepardjo² (1.Indonesian National Research and Innovation Agency, 2.Indonesian University)

Keywords:diffuse attenuation coefficient, euphotic zone depth, Mahakam Delta

This study was performed to estimate the vertical diffuse attenuation coefficient and the euphotic zone depth of the Mahakam Delta, as an indicator of the quality of the delta’s aquatic ecosystem. The vertical diffuse attenuation coefficient K_d is directly related to the euphotic zone depth: a cumulative measure of the biogeochemical properties of the water column. Two analytical methods were used to estimate K_d, and inter-compared, hereafter called the Lee and 2F methods. IOP estimated from previous research in the Mahakam Delta were taken as an input. A validation with in-situ measurement in the Mahakam delta shows that the Lee and the 2F methods to estimate the diffuse attenuation coefficient give similar results. Our results indicate that the Mahakam Delta shows high CDOM concentrations, where the relation between photosynthetically active radiation (PAR) and the attenuation coefficients at 550 and 670 nm give the best results. High attenuations can be found within the distributaries. The euphotic depth in the tidal part of the delta can reach around 7 m, though the bathymetry depth is 5 m, while the euphotic zone depths in the distributaries are less than 2 m. CDOM absorption was found as the main factor in the diminution of light within the Mahakam Delta waters. The results of this study can contribute to a potentially operational method based on remote sensing data to monitor primary productivity.