ESTIMATION OF CHLOROPHYLL-A CONCENTRATION ON OLIGOTROPHIC OPEN WATERS OF THE PHILIPPINES: A CASE STUDY FOR POLILIO

ABSTRACT: It has been demonstrated by various groups (Huang 2010, Gitelson 2011) that the chlorophyll-a concentration can be estimated using the measured water-leaving reflectance of sea/ocean waters. In this work, the chlorophyll a concentration in oligotrophic open waters of Polilio in Quezon province was derived using the band ratios of measured water-leaving reflectance. There were seven sampling sites used in this study, all located at depths greater than 40 m. The highest correlations between the band ratios and in situ chlorophyll a values were achieved at 570-nm/665-nm, with R-squared of 0.9329 and Pearson coefficient of 0.9659. Correlating the in situ chlorophyll-a values with the Moderate Resolution Imaging Spectroradiometer (MODIS) chlorophyll-a product resulted to an R-squared of 0.4261 and Pearson coefficient of 0.6528. These results suggest the efficacy of using multispectral band ratios to estimate chlorophyll a concentration in real-time with high accuracy for oligotrophic open waters. 1