Distribution of extant coccolithophores from the northwest continental shelf of India during the summer monsoon

ABSTRACT

Coccolithophores contribute substantially to marine primary production as well as to particulate inorganic carbon (PIC) flux to the deep sea; however, there is no literature available so far from the Indian continental shelf on this functional group. We present here the first study describing the spatial variability and species composition of living coccolithophore communities from the north-western continental shelf waters (northeastern Arabian Sea) of India (SW monsoon; August 2018). We found a total of 18 species from 11 genera with Gephyrocapsa oceanica as the dominant coccolithophore. Florisphaera profunda, Calcidiscus leptoporus, Helicosphaera carteri and Umbilicosphaera sibogae were also observed in significant quantities in most of the stations. Cell abundances ranged from 0.3 to 85.6 × 10³ l^–1 with the maximum occurrence at the northernmost station. Coccolithophore diversity was comparatively higher in the southernmost region, while high dominance was noticed in the north. Redundancy analysis (RDA) revealed that nutrient availability was an important factor to modulate the distribution and abundance of coccolithophores. Gephyrocapsa oceanica was recorded in each station and showed a positive association with NO₂^– + NO₃^– levels, whereas F. profunda and U. sibogae were confined mostly to deepwater. Our study shows that a substantial number of coccolithophores are present in the shelf water and could be important as primary producers as well as for the carbon export flux. Further research attention to broaden our knowledge of the role of this functional group is warranted.

KEYWORDS:

• Arabian Sea
• Coccolithophore diversity
• Florisphaera profunda
• Gephyrocapsa oceanica
• SW Monsoon

ACKNOWLEDGEMENTS

We thank the Director, CSIR NIO, for his support. We thank Mr. Areef Sarder for his kind cooperation and technical help during the SEM analysis. We also acknowledge the active support from the captain, scientists, technical staff, ship cell staff, crew members, deckhand and the students onboard RV Sindhu Sadhna (SSD 55).

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

SUPPLEMENTARY MATERIAL

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

This study was conducted under the Council of Scientific and Industrial Research (CSIR) funded project (MLP 1802). The financial supports provided by CSIR, University Grant Commission (UGC-India), and Department of Science and Technology (DST-India) for the first, third and fourth authors, respectively, are gratefully acknowledged. NIO contribution number for this paper is 6877.