Phytoplankton response to the contrasting physical regimes in the eastern Arabian Sea during north east monsoon

Chndrasekhararao, A.V.; Kurian, Siby; Vidya, P.J.; Gauns, Mangesh; Shenoy, Damodar M.; Mulla, Amara Begum; Naik, Hema; Reddy, T. Venugopal; Naqvi, S.W.A.

doi:10.1016/j.jmarsys.2018.02.002

Cited by 13 publications

(2 citation statements)

References 36 publications

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“…A higher abundance of picophytoplankton with a predominance of Synechococcus has also been reported during the winter period in the northern Arabian Sea. Chndrasekhararao et al 27 also observed low microphytoplankton concentration in 2017 when the Si/DIN ratio was low and suggested that Si/DIN ratio controls the phytoplankton composition in the northeastern Arabian Sea. The absence of diatoms 19 and Noctiluca 22 , which are known to contribute towards high productivity during the winter monsoon, had a bearing on the column productivity.…”

Section: Resultsmentioning

confidence: 97%

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Physicochemical controls on the initiation of phytoplankton bloom during the winter monsoon in the Arabian Sea

Lakshmi

Prakash

Lotliker

et al. 2021

Sci Rep

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Occurrence of phytoplankton bloom in the northern Arabian Sea (NAS) during the winter monsoon is perplexing. The convective mixing leads to a deeper and well-oxygenated (> 95% saturation) mixed layer. We encountered low chlorophyll conditions though the nutrient conditions were favorable for a bloom. The mean ratio of silicate (Si) to DIN (Dissolved Inorganic Nitrogen: nitrate + nitrite + ammonium) in the euphotic zone was 0.52 indicating a “silicate-stressed” condition for the proliferation of diatoms. Also, the euphotic depth was much shallower (~ 49 m) than the mixed layer (~ 110 m) suggesting the Sverdrup critical depth limitation in the NAS. We show that the bloom in this region initiates only when the mixed layer shoals towards the euphotic zone. Our observations further suggest that two primary factors, the stoichiometric ratio of nutrients, especially the Si/DIN ratio, in the mixed layer and re-stratification of the upper water column, govern the phytoplankton blooming in NAS during the later winter monsoon. The important finding of the present study is that the Sverdrup’s critical depth limitation gives rise to the observed low chl-a concentration in the NAS, despite having enough nutrients.

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Section: Resultsmentioning

confidence: 97%

“…The Noctiluca blooms also have been reported to be associated with dissolved oxygen depletion and fish mortality 2 , 26 . The absence of diatoms and Noctiluca in the water column can severely impact the total primary production in the northern Arabian Sea during the winter monsoon 19 , 22 , 27 .…”

Section: Introductionmentioning

confidence: 99%