Publications

Sarangi, RK; Jaiganesh, SNN; Patel, BR; Prajapati, A; Patel, HD (2023). Particulate Organic Carbon (POC) Estimation and Algorithm Development in Northeast Arabian Sea Coastal Water. THALASSAS.

Abstract
In situ sampling and analysis for water quality and bio-optical parameters carried out in the northeast Arabian Sea, in Diu and Daman coastal waters during February and August 2021. The in situ water samples analysed to estimate chlorophyll, nutrients, Particulate Organic Carbon (POC) in the study area. The bio-optical parameters, normalized water leaving radiance (L-wn) and remote sensing reflectance (R-rs) retrieved with the operation of underwater hyperspectral radiometer (Satlantic/Wetlabs Inc). The objective of the study was to develop POC algorithm in coastal waters of northwest Arabian Sea, utilizing the datasets from sampled Gujarat coastal water stations and the use of underwater hyperspectral radiometer measured remote sensing reflectance (Rrs) data and in situ POC data covering different months and seasons, applying suitably optimal wavelengths-based algorithms and its finalization. In Diu, total 11 stations data collected and produced POC range (44-608 mg m(-3)). These 11 points POC data correlated with R-rs band ratios using 2nd order polynomial function and indicated coefficient of determination (R-2 values 0.37, 0.34 and 0.13). This correlation was also made using 3rd order polynomial fit and indicated R-2 values 0.41, 0.42 and 0.26. The same datasets were observed with 3-Dimensional correlation between R-rs(490/555), R-rs(443/555), R-rs(510/555) and POC using linear, paraboloid, gaussian and Lorentzian function fit, which showed improved R-2 values ranging 0.34 to 0.66. The data from Daman added to Diu data (total 18 points), which resulted with further better correlation (R-2 = 0.75, RMSE = 9.12) with higher range of POC upto 2600 mg/m(3). This used multiple linear regression (MLR) between blue and green wavelength channels and band ratios (490, 510, 555, 490/555 and 510/555) derived POC versus the in situ POC data. The Modis-Aqua satellite derived POC data for our in situ stations for the sampling dates ranged 392-411 mg m(-3) as compared to our in situ data range 44-608 mg m(-3). Out of these different POC algorithms inter-comparison and linkage to satellite data, it observed mandatory to have regional POC algorithms with sufficient in situ data points. The coastal water productivity and its variability study is essential in terms of POC mapping and monitoring on monthly and seasonal time scales in regional scale due to the various fluxes, phytoplankton dynamics and sources from rivers, industries, upwelling and coastal ocean processes.

DOI:
10.1007/s41208-023-00587-w

ISSN:
2366-1674