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(l)]
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(l) 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(l) with Chl a dominates the
behavior of the Rrs(l) peak in these blooms.