Distinctive phytoplankton size responses to the nutrient enrichment of coastal upwelling and winter convection in the eastern Arabian Sea

Albin, K.J.; Jyothibabu, R.; Alok, K.T.; Santhikrishnan, S.; Sarath, S.; Sudheesh, V.; Sherin, C. K.; Balachandran, K.K.; Devi, C.R. Asha; Gupta, G.V.M.

doi:10.1016/j.pocean.2022.102779

Cited by 26 publications

(2 citation statements)

References 133 publications

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“…4). Arabian Sea is generally less productive during the pre-monsoon season leading to low primary and secondary production (Gupta et al, 2016;Albin et al, 2022). NMDS analysis revealed three clusters of sampling points in M1 and M2 in 2014 whereas in M3 it was two clusters.…”

Section: Discussionmentioning

confidence: 99%

Microbial distribution in Mudbank regions off Alappuzha, South-west coast of India

Vijayan,

Ammini,

Sri

et al. 2024

Preprint

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The coastal waters of Kerala, in the South Eastern Arabian Sea (SEAS), are unique during the Southwest monsoon season due to the concurrent occurrence of two physical processes, the upwelling and Mudbanks. However, little is known about the viral ecology and activity in a system where upwelling and mudbanks coexist, though it is generally recognized that microbial assemblages play a vital role in the food web dynamics of marine systems, particularly in upwelling. Water samples were taken from three locations, M1, M2, and M3, off Alappuzha, on the southwest coast of India to examine the viral activity and distribution. An 18-week study in 2014 and a 16-week study in 2016 on a weekly/biweekly interval were carried out from April to September, which were categorized into three seasons April to May, as pre-monsoon, June to August as monsoon, and September period as late-monsoon. The dissolved oxygen levels showed the incursion of hypoxic waters in all the stations during the peak upwelling period. Upwelling signals were prominent in all the stations, but Mudbank and upwelling co-occurred at M2 alone during monsoon. The abundance of viruses ranged from 0.86 to 15.68×106 Viral like Particles (VLPs mL-1) and prokaryotic abundance ranged from 2.73-16.26×105 cells mL-1. Viral and prokaryotic abundance was significantly higher in the monsoon compared to pre and late-monsoon. Based on Transmission electron microscopy (TEM) results, the non-tailed viruses constituted the major (43%) proportion of the total viruses during this study region. However, the viral production rates and viral-mediated bacterial mortality were high in the pre-monsoon compared to the monsoon and late-monsoon periods. There was no obvious effect of Mudbanks on viral dynamics and the observed variations in virological and hydrological features were governed mainly by coastal upwelling.

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Section: Discussionmentioning

confidence: 99%

Microbial distribution in Mudbank regions off Alappuzha, South-west coast of India

Vijayan,

Ammini,

Sri

et al. 2024

Preprint

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“…However, during the post-monsoon (PM) period, generally unstable conditions prevail throughout the WCI [5]. Higher chlorophyll a concentrations have been reported during PM and MN with respect to monsoon [6]. During MN and PM, various mechanisms govern water-column mixing, nutrient upwelling, with subsequent increase in phytoplankton biomass [7], [8], [9], [10], [11], [12].…”

Section: Introductionmentioning

confidence: 99%

Article Seasonal Surges in Bacterial Diversity along the Coastal Waters of the Eastern Arabian Sea

Hafza,

Parvathi,

Pradeep Ram

et al. 2024

Preprint

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The upwelling phenomenon plays a vital role within marine ecosystems, transporting essential nutrients from the bottom to the surface and boosting biological productivity. However, the bacterial community structure in upwelling zones along Western coast of India (WCI) is under-studied. This research systematically examines bacterial diversity across three sea-sons—Pre-monsoon (PR), Monsoon (MN), and Post-monsoon (PM)—using next-generation se-quencing. Our findings show distinct spatial patterns of bacterial communities in the Arabian Sea and demonstrate that ecological variations influence bacterial distribution in this dynamic envi-ronment. During MN, the bacterial community was notably distinct and diverse than during PR and PM, despite their lower abundance in MN. Non-Metric MDS cluster analysis revealed a 78% similarity (at order level) between PR and PM, indicating MN supports unique bacterial diversi-ty. KEGG analysis showed significant seasonal variations in metabolic functions, with increased functional potential during MN. Additionally, Carbohydrate-Active enZymes (CAZymes) analy-sis revealed distinct seasonal profiles, among which the GH13 enzymes were the most prevalent glycoside hydrolases during MN; predominantly sucrose phosphorylase and glucosidase, known for breaking down glucan deposits derived from phytoplankton. The CAZymes profiles sup-ported taxonomic and KEGG pathway findings, reinforcing that microbial communities are sea-sonally distinct and functionally adapted to changing availability of nutrients.

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Winter convective mixing regulates oceanic C : N : P ratios

Sahoo,

Saxena,

Nazirahmed

et al. 2024

Limnology & Oceanography

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Recent studies have challenged the validity of the Redfield ratio. It is proposed that physical and biogeochemical processes govern the geographical variations in carbon : nitrogen : phosphorus (C : N : P) ratios. However, this proposal remains to be examined through concurrent observations of C : N : P ratios with physical and biogeochemical processes in various marine reservoirs. Here, we sampled the Arabian Sea for its C, N, and P content in organic and inorganic pools during the winter monsoon. We analyzed the role of convective mixing, eddies, and N2 fixation to explain the variation in observed elemental ratios. Convective mixing injected the cold water and enhanced the supply of N and P nutrients in the top layer (surface to 50–75 m) of the northern Arabian Sea. This led to a decrease in the N : P and C : P ratios in the particulate organic matter in the northern region, but C : N : P increased equatorward, averaging 245 : 32 : 1 in the top layer of the Arabian Sea. The variation in the elemental ratios in the top layer is best explained by the changes in water temperature. N2 fixation contributed negligibly to the N : P ratio of the export flux. The substantial decrease in N : P ratios of nutrients in the subsurface waters is most likely caused by the denitrifying conditions in the Arabian Sea. As the processes of convective mixing and eddies are are prevalent oceanic processes, our observations underpin that the interplay of these processes leads to changes in the elemental ratios globally.

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Distinctive phytoplankton size responses to the nutrient enrichment of coastal upwelling and winter convection in the eastern Arabian Sea

Cited by 26 publications

References 133 publications

Microbial distribution in Mudbank regions off Alappuzha, South-west coast of India

Microbial distribution in Mudbank regions off Alappuzha, South-west coast of India

Article Seasonal Surges in Bacterial Diversity along the Coastal Waters of the Eastern Arabian Sea

Winter convective mixing regulates oceanic C : N : P ratios

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