Distribution of Coloured Dissolved and Detrital Organic Matter in Optically Complex Waters of Chilika Lagoon, Odisha, India, using Hyperspectral Data of AVIRIS-NG

Coloured dissolved and detrital matter (CDM) forms a significant fraction of the total dissolved organic matter (DOM) in water bodies. It absorbs light strongly in the ultraviolet and blue domains of the electromagnetic spectrum. The present study maps CDM absorption of the entire Chilika lagoon, Odisha, India (an optically complex water body) using hyperspectral data of AVIRIS-NG. This study takes advantage of hyperspectral data which use SWIR bands for the estimation of remote sensing reflectance in highly turbid waters of Chilika lagoon (northern sector, which otherwise is masked using standard atmospheric correction schemes). During 24–27 December 2015, we have collected in situ bio-optical data over waters of Chilika lagoon, for studying the distribution of CDM. AVIRIS-NG data have also been acquired synchronous to in situ measurements over the study area. CDM absorption coefficient is retrieved using quasi analytical algorithm and the distribution of CDM is discussed in detail in three different sectors of Chilika lagoon (southern, central, northern) and at the outer channel. The variability of CDM absorption at 412 nm shows that in the north sector of Chilika lagoon, CDM absorption is quite high compared to other sectors (5.5 m^–1 with a standard deviation of 0.06 m^–1). In the southern sector and at the outer channel it is 1.8 m^–1 with a standard deviation of 0.02 m^–1 and in the central sector it is 3.76 m^–1 with a standard deviation of 0.22 m^–1. High CDM in the northern sector is attributed to the inflow of terrestrial organic matter. The advantage of hyperspectral data is that it gives CDM absorption contiguous in the range of 375–425 nm, where the absorption by CDM is strong and away from chlorophyll-a absorption.