Occurrence and Distribution of a Diatom-Diazotrophic Cyanobacteria Association during a Trichodesmium Bloom in the Southeastern Arabian Sea

T Jabir,M P Prabhakaran,V Dhanya,A A M Hatha,G V M Gupta,Y Jesmi,N Saravanane

doi:10.1155/2013/350594

T Jabir, M P Prabhakaran + Show 5 more

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https://doi.org/10.1155/2013/350594

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Abstract

Symbiotic diatom-diazotrophic cyanobacteria association (DDA) of Rhizosolenia hebetata and Rhizosolenia formosa with endosymbiotic cyanobacteria Richelia intracellularis was noticed and documented for the first time during a bloom of the cyanobacterium Trichodesmium erythraeum in the oligotrophic shelf waters along Kochi and Mangalore transects, southeastern Arabian Sea (SEAS), during spring intermonsoon (April 2012). Although the host is frequently seen, the symbiont is rarely reported in the Indian EEZ. The presence of nitrogen-fixing symbiotic association of Rhizosolenia-Richelia along with Trichodesmium erythraeum highlights the significance of DDAs on the nutrient and energy budgets of phytoplankton in the oligotrophic environments of the Arabian Sea during spring intermonsoon.

Highlights

Planktonic organisms that fix atmospheric nitrogen have a critical role in oceanic production and in the marine nitrogen cycle [1]
The study was a part of monthly observations made in the southeastern Arabian Sea (SEAS), and observations made along the Kochi and Mangalore transects during April 2012 are reported in this paper (Figure 1)
In the present study, R. intracellularis was found to be symbiotic in Rhizosolenia hebetata and R. formosa

Summary

Introduction

Planktonic organisms that fix atmospheric nitrogen (diazotrophs) have a critical role in oceanic production and in the marine nitrogen cycle [1]. Diatom-diazotroph associations (DDAs) are widely reported in oligotrophic waters and have the capacity to form episodic, largely monospecific blooms that exhibit very high rates of carbon and nitrogen fixation worldwide [4,5,6,7]. A unique group of open ocean diazotrophs is the heterocystous cyanobacteria that live symbiotically with other members of phytoplankton, primarily diatoms Such endosymbiotic associations help most of the diatoms to fix atmospheric nitrogen in oligotrophic waters with the help of such endosymbiotic associations [11,12,13]. The cyanobacteria, Richelia intracellularis and Calothrix rhizosoleniae, were found in association with diatom genera such as Rhizosolenia, Hemiaulus, Bacteriastrum, and Chaetoceros They are seen as epiphyte or endosymbiont in Guinardia cylindrus in warm tropical and subtropical oligotrophic waters [6, 12, 14].

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Results and Discussion

Conclusion