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Not AvailablePhytoplankton size structure influences the underwater light field and determines the fate of carbon in a pelagic food chain. Temporal and vertical variations of size fractionated chlorophyll a concentration (Chl-a) were investigated along coastal region off Kochi from May 2013 to April 2014 in order to understand the influence of environmental parameters on phytoplankton size distribution in coastal waters of South-eastern Arabian Sea. The study identified abundance of microphytoplankton around 10m depth, nanophytoplankton from surface to 5m depth and picophytoplankton in 10-20m water column. The results also showed that increased nitrate and phosphate concentration favoured nanophytoplankton growth and increased silicate concentration favoured the growth of microphytoplankton. Pre-showers and extended southwest monsoon along with variation in nutrient concentrations in the area during the study period significantly influenced the variation in size fractionated chlorophyll, absorption by phytoplankton and its numerical density. The results will provide an insight into the chemical factors that control the production cycle in this neritic system and can be used to improve the size fraction algorithms for various societal applications of remote sensingNot Availabl

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Not AvailableThe ability of hyper spectral optical measurements to discriminate changes in the composition of phytoplankton communities in coastal waters is well studied. The performance of spectral fourth derivative analysis and clustering techniques to differentiate four different algal blooms is done. Phytoplankton absorption coefficient , aph, and remote-sensing reflectance, Rrs are used in the analysis. Samples were collected on monthly basis from coastal waters off Kochi. Similarity index was applied to measured spectra of aph and Rrs. Similarities between abundance-based and optically-based classifications were better for the optical data of Rrs than aph. This analysis showed that, hyperspectral Rrs can be used as a potentially suitable input data for the differentiation of phytoplankton taxonomic groups. These results suggest using of hyperspectral optical data of aph and Rrs with derivative spectroscopy as a promising approach to identify bloom forming phytoplankton in coastal waters.Not Availabl

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Not AvailableOcean 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.Not Availabl

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Not AvailableA study was performed on the coastal waters of the southeastern Arabian Sea to understand the changes in the inherent properties of optically active substances (OAS). The objective of this study was to obtain insight into the temporal dynamics of OASs for various remote sensing applications. Both the absorption of light by phytoplankton (aph(440)) and detritus (ad(440)) varied the 2nd orders of magnitude, whereas the absorption of light by chromophoric dissolved organic matter (CDOM; aCDOM(440)) exhibited an increasing trend over the years. aCDOM(440) increased from 2009 to 2015 at a rate 0.012 m−1 year−1. The validation of the satellite data with in situ data indicated that ad(443) underestimated the in situ ad(443) when the in situ ad(443) was less than 0.3 m−1. The ternary analysis of ocean-colour-climate-change initiative (OC-CCI)–derived inherent optical properties (IOP) during the postmonsoon season indicated increased contribution by ad(443). Detritus was the primary light absorber in the coastal waters of Kochi followed by phytoplankton and CDOM. These long-term data sets and their seasonal variation will enable development of seasonal specific regional algorithms for chlorophyll-a, which are employed in potential fishing zone advisories and other applications.Not Availabl

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Not AvailableColoured dissolved organic matter (CDOM) plays a major role in marine photochemical and biological processes and its optical properties are known to affect the underwater light penetration. This paper highlights in situ optical estimation and satellite retrieval of CDOM in deciphering its temporal variations in coastal waters of the South Eastern Arabian Sea. The study accentuated the source of CDOM as terrigenous origin during monsoon, of in situ productions during pre-monsoon and during post-monsoon of autochthonous-allocthonous origin. The matchup analysis for in situ and MODIS Aqua retrieved Adg443 exhibited bias which decreased by incorporating the seasonal component. The study also identified degrading bloom of Noctiluca scintillans as the source for exceptionally high CDOM in the area during January and February. The study demands to incorporate seasonal components and phytoplankton abundance while assessing the performance of CDOM algorithms in optically complex coastal waters.Not Availabl