Culturable bacterial flora associated with the dinoflagellate green Noctiluca miliaris during active and declining bloom phases in the Northern Arabian Sea

Show simple item record Basu, S. Deobagkar, D.D. Matondkar, S.G.P. Furtado, I. 2013-06-17T06:34:57Z 2013-06-17T06:34:57Z 2013
dc.identifier.citation Microbial Ecology, vol.65; 2013; 934-954
dc.description.abstract A massive algal bloom of the dinoflagellate Noctiluca miliaris (green) was located in the Northern Arabian Sea by IRS-P4-2 (OCM-II) for microbiological studies, during two consecutive cruises of February-March 2009. Culturable bacterial load during bloom were approx. 2-3-fold higher in comparison to non-bloom waters and ranged from 3.20×10 sup(5) to 6.84×10 sup(5) cfu ml sup(-1). An analysis of the dominant heterotrophs associated with Noctiluca bloom resulted in phylogenetic and a detailed metabolic characterization of 70 bacterial isolates from an overlapping active and declining bloom phase location near north-central Arabian Sea. The active phase flora was dominated by Gram-positive forms (70.59 percent), a majority of which belonged to Bacillus (35.29 percent) of Firmicutes. As the bloom declined, Gram-negative forms (61.11 percent) emerged dominant, and these belonged to a diverse γ-proteobacterial population consisting of Shewanella (16.67 percent) and equal fractions of a Cobetia-Pseudomonas-Psychrobacter-Halomonas population (36.11 percent). A Unifrac-based principal coordinate analysis of partial 16S rDNA sequences showed significant differences among the active and declining phase flora and also with reported endocytic flora of Noctiluca (red). A nonparametric multidimensional scaling (NMDS) of antibiogram helped differentiation among closely related strains. The organic matter synthesized by N. miliaris appears to be quickly utilized and remineralized as seen from the high efficiency of isolates to metabolize various complex and simple C/N substrates such as carbohydrates, proteins/amino acids, lipids, sulfide production from organic matter, and solubilize phosphates. The ability of a large fraction of these strains (50-41.67 percent) to further aerobically denitrify indicates their potential for nitrogen removal from these high-organic microniches of the Noctiluca bloom in the Arabian Sea, also known for high denitrification activity. The results indicate that culturable euphotic bacterial associates of Noctiluca are likely to play a critical role in the biogeochemical ramifications of these unique seasonally emerging tropical open-water blooms of the Northern Arabian Sea.
dc.language.iso en
dc.publisher Springer
dc.rights An edited version of this paper was published by Springer. This paper is for R & D purpose and Copyright [2013] Springer.
dc.subject algal blooms
dc.subject bacteria
dc.subject ecological associations
dc.subject remote sensing
dc.title Culturable bacterial flora associated with the dinoflagellate green Noctiluca miliaris during active and declining bloom phases in the Northern Arabian Sea
dc.type Journal Article

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