Influence of warm core eddy on the vertical distribution of autotrophic pico- and nanoplankton in the Bay of Bengal

ABSTRACT

The distribution and ecology of autotrophic pico- and nanoplankton were studied in the warm core eddy-affected northern Bay of Bengal (BoB) during the peak south-west monsoon of 2012. Small phototrophs showed diverse response patterns to the contrasting environmental setting in the northern BoB during the south-west monsoon. The convergence of surface waters in the eddy-influenced region was evidenced in terms of a deeper mixed layer and lower concentrations of $\mathrm{N}{\mathrm{O}}_3^{-}$. Synechococcus and picoeukaryotes were found to be more abundant in coastal waters as compared with the warm core eddy-influenced and offshore waters. Prochlorococcus was more abundant in the eddy-influenced and the offshore regions possibly as a consequence of their ability to survive in low-nutrient/oligotrophic waters. The abundance of Synechococcus increased noticeably in the coastal and subsurface waters due to their affinity towards higher concentrations of nutrients. The present data therefore support the view of a community shift induced by warm core water eddies and show their importance in promoting primary production by Prochlorococcus in the mixed layers of the BoB.

KEYWORDS:

• Warm core eddy
• distribution
• picoplankton
• nanoplankton
• Bay of Bengal

Acknowledgements

The authors thank Professor Sunil Kumar Singh, Director, CSIR-National Institute of Oceanography, Goa and Scientist-In-Charge, CSIR-National Institute of Oceanography, Regional Centre, Kochi for supporting our study. The financial assistance from Ministry of Earth Science, New Delhi is gratefully acknowledged. We thank Dr R. Jyothibabu, Dr Jagadeeshan L, Dr Karnan C and Arunpandi N (National Institute of Oceanography, Regional Centre, Kochi) for their support. We record our sincere thanks to all the National Institute of Oceanography staff, who participated in the fieldwork in the Bay of Bengal in July–August 2012.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Ministry of Earth Sciences, New Delhi, India