Hyperspectral Variability of Phytoplankton Blooms in Coastal Waters off Kochi, South-eastern Arabian Sea

Abstract

Ocean colour radiometry offers cost-effective, frequently acquired synoptic data pertaining to phytoplankton biomass in surface waters and is of considerable value in monitoring and better understanding of algal blooms. Algal blooms have occur frequently in coastal waters resulting in severe negative impacts to local marine ecosystems and communities. Remote sensing reflectance [Rrs(λ)] and absorption coefficients of phytoplankton blooms were measured in coastal waters off Kochi, Southeastern Arabian Sea, to investigate differences in the absorption and reflectance of different types of blooms. Peaks of the Rrs(λ) spectra of Trichodesmium spp. bloom were at 490 nm, while those of nonbloom areas were 482, 560 and 570 nm. The absorption maximam of phytoplankton were at 435, 437, 438 and 439 nm in the blue region and 632, 674, 675 and 635 nm in the red region respectively for Trichodesmium spp., Chaetoceros spp., Dinophysis spp. and Prorocentrum spp. blooms. The study showed that the variation of aph(λ) with Chl a dominates the behavior of the Rrs(λ) peak in these blooms.