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Marine Ecology Progress Series

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MEPS 653:41-55 (2020)  -  DOI:

Non-Redfieldian C:N:P ratio in the inorganic and organic pools of the Bay of Bengal during the summer monsoon

Deepika Sahoo1,2, Himanshu Saxena1,2, Nidhi Tripathi1,2, Mohammad Atif Khan1, Abdur Rahman1, Sanjeev Kumar1, A. K. Sudheer1, Arvind Singh1,*

1Physical Research Laboratory, Ahmedabad, Gujarat 380009, India
2Indian Institute of Technology, Gandhinagar, Gujarat 382355, India
*Corresponding author:

ABSTRACT: Nitrogen (N) and phosphorus (P) determine the strength of the ocean’s biological carbon (C) pump, and variation in the N:P ratio is key to phytoplankton growth. A fixed C:N:P ratio (106:16:1) in organic matter and deep-water nutrients was observed by Alfred C. Redfield. However, recent studies have challenged the concept of the Redfield Ratio, and its veracity remains to be examined in oceanic basins like the Bay of Bengal. For this purpose, we sampled the water in the Bay of Bengal for C, N, and P content in the organic and inorganic pools from the surface to 2000 m. Overall, the C:N:P ratio deviated greatly from the Redfield Ratio. The C:N:P ratio in particulate organic matter varied from 232:25:1 in the top layer (surface to the depth of the chlorophyll maximum) to 966:72:1 in the deep water (300-2000 m). In dissolved organic matter, the ratio varied from 357:30:1 in the top layer to 245:66:1 in the deep water. The N:P ratio in nutrients varied from 3 in the top layer to 12 in the deep water. The nutrient-depleted top layer (average NO3- + NO2- ~ 0.7 µmol l-1) with a low N:P ratio coupled with reported low primary production rates in the Bay suggested that the production was N limited. Concurrent N2 fixation rates were not sufficient to alter the observed C:N:P ratio. Eddies showed a mixed effect on the C:N:P ratio. Our C:N:P ratios in particulate organic matter are comparable to other tropical basins and supports the nutrient supply hypothesis for low latitude ecosystems.

KEY WORDS: Northern Indian Ocean · Elemental stoichiometry · Organic matter · Nitrogen limitation

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Cite this article as: Sahoo D, Saxena H, Tripathi N, Khan MA and others (2020) Non-Redfieldian C:N:P ratio in the inorganic and organic pools of the Bay of Bengal during the summer monsoon. Mar Ecol Prog Ser 653:41-55.

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