Trichodesmium blooms and warm-core ocean surface features in the Arabian Sea and the Bay of Bengal

Jyothibabu, R.; Karnan, C.; Jagadeesan, L.; Arunpandi, N.; Pandiarajan, R.S.; Muraleedharan, K. R.; Balachandran, K.K.

doi:10.1016/j.marpolbul.2017.06.002

Cited by 35 publications

(15 citation statements)

References 67 publications

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“…Our RF-model predicts high abundance of diazotrophs in the tropical and subtropical waters near Madagascar and off the coast of western Australia, which is consistent with field observations of Trichodesmium and unicellular diazotrophs blooms in these areas (Holl et al, 2007;Poulton et al, 2009;Srokosz & Quartly, 2013). In comparison, Monteiro et al (2010) and Paulsen et al (2017) simulate abundant diazotrophs in the Arabian Sea and the Bay of Bengal, which is supported by some studies (Jyothibabu et al, 2017). While noncyanobacterial diazotrophy is currently not simulated in any of the models, recent studies have highlighted their potentially overlooked importance in the Indian Ocean (Bird & Wyman, 2013;Shiozaki, Ijichi, et al, 2014;Wu et al, 2019).…”

Section: Machine Learning Estimates and Comparison To Other Model Simsupporting

confidence: 90%

Data‐Driven Modeling of the Distribution of Diazotrophs in the Global Ocean

Tang

Cassar

2019

Geophysical Research Letters

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Diazotrophs play a critical role in the biogeochemical cycling of nitrogen, carbon, and other elements in the global ocean. Despite their well‐recognized role, the diversity, abundance, and distribution of diazotrophs in the world's ocean remain poorly characterized largely due to limited observations. Here we update the database of diazotroph nifH gene abundances and assess how environmental factors may regulate diazotrophs at the global scale. Our meta‐analysis more than doubles the number of observations in the previous database. Using linear and nonlinear regressions, we find that the abundances of Trichodesmium, UCYN‐A, UCYN‐B, and Richelia relate differently to temperature, light, and nutrients. We further apply a random forest algorithm to estimate the global distributions of these diazotrophic groups, identifying undersampled potential hot spots of diazotrophy in the South Atlantic and southern Indian Ocean, and in coastal waters. The distinct ecophysiologies of diazotrophs highlighted here argue for separate parameterizations of different diazotrophs in model simulations.

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Section: Machine Learning Estimates and Comparison To Other Model Simsupporting

confidence: 90%

Data‐Driven Modeling of the Distribution of Diazotrophs in the Global Ocean

Tang

Cassar

2019

Geophysical Research Letters

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“…Homogenizing dispersal results from high levels of organism exchange ( Stegen et al, 2015 ). Ocean current transportation and frequently occurred mesoscale surface ocean features (eddies) in the EIO ( Jyothibabu et al, 2017 ) may introduce more exchanges of water mass and change the opportunities of species interactions. Several research have proved the importance of stochastic processes.…”

Section: Discussionmentioning

confidence: 99%

“…As one of the largest oligotrophic areas, the Indian Ocean plays an essential role in global climatic change, material cycles, and energy flow ( Schott et al, 2009 ). Winds and currents over the Eastern Indian Ocean (EIO) are seasonally reversed during the southwest monsoon (June–September) and northeast monsoon (October–February) with a clear transition phase, namely, the intermonsoon (March–May) ( Jyothibabu et al, 2017 ). In monsoon, upwelling and convective mixing driven by seasonal monsoon winds could increase upward transportation of nutrients, resulting in seasonal blooms of phytoplankton ( Lévy et al, 2007 ; Singh and Ramesh, 2015 ; Pujari et al, 2019 ).…”

Section: Introductionmentioning

confidence: 99%

Assembly Processes and Co-occurrence Patterns of Abundant and Rare Bacterial Community in the Eastern Indian Ocean

Pujari

et al. 2021

Front. Microbiol.

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Microbial communities are composed of many rare species and a few abundant species. Considering the disproportionate importance of rare species for ecosystem functioning, it is important to understand the mechanisms structuring the rare and abundant components of a diverse community in response to environmental changes. Here, we used a 16S ribosomal RNA gene sequencing approach to investigate the bacterial community diversity in the Eastern Indian Ocean (EIO) during the monsoon and intermonsoon. We employed a phylogenetic null model and network analysis to evaluate the assembly processes and co-occurrence pattern of the microbial community. We found that higher bacterial diversity was detected in the intermonsoon with high temperature and low Chlorophyll a concentrations and N/P ratios. The balance between ecological deterministic processes and stochastic processes varied with seasons in the EIO. Meanwhile, conditionally rare taxa (CRT) were more likely modulated by variable selection processes than always rare taxa (ART) and abundant taxa (AT) (CRT > ART > AT). By linking assembly process and species co-occurrence, we demonstrated that the microbial co-occurrence associations tended to be higher when deterministic processes (mainly variable selection) were weaker. This negative trend was observed in rare species rather than abundant species. The linkage could enhance our understanding of the underlying mechanisms underpinning the generation and maintenance of microbial community diversity.

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“…Besides those small cyanobacteria, there are reports on nitrogen fixing cyanobacteria of the Trichodesmium clade (Devassy, Bhattathiri, and Radhakrishna 1983;Jyothibabu et al 2017;Sahu et al 2017;Hegde et al 2008;Shetye et al 2013;Wu et al 2019); other reports included diatom-diazotroph associations playing a role for BoB nitrogen fixation (Bhaskar et al 2007).…”

Section: Key Primary Producers In Bob Watersmentioning

confidence: 99%

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Löscher¹

2021

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Ocean primary production is the basis of the marine food web, sustaining life in the ocean via photosynthesis, and removing carbon dioxide from the atmosphere. Recently, a small but significant decrease of global marine primary production has been reported based on ocean color data, which was mostly ascribed to decreases in primary production in the northern Indian Ocean, particularly in the Bay of Bengal.Available reports on primary production from the Bay of Bengal (BoB) are limited, and due their spatial and temporal variability difficult to interpret. Primary production in the BoB has historically been described to be driven by diatom and chlorophyte clades, while only more recent datasets also show an abundance of smaller, visually difficult to detect cyanobacterial primary producers. The different character of the available datasets, i.e. direct counts, metagenomic and biogeochemical data, and satellite-based ocean color observations, make it difficult to derive a consistent pattern. However, making use of the most highly resolved dataset based on satellite imaging a shift in community composition of primary producers is visible in the BoB over the last two decades. This shift is driven by a decrease in chlorophyte abundance, and a coinciding increase in cyanobacterial abundance, despite stable concentrations of total chlorophyll. A similar but somewhat weaker trend is visible in the Arabian Sea, where satellite imaging points towards decreasing abundances of chlorophytes in the North and increasing abundances of cyanobacteria in the eastern parts. Statistical analysis indicated a correlation of this community change in the BoB to decreasing nitrate concentrations, which may provide an explanation for both, the decrease of eukaryotic nitrate-dependent primary producers and the increase of small unicellular cyanobacteria related to Prochlorococcus, which have a comparably higher affinity to nitrate. Changes in community composition of primary producers and an overall decrease of system productivity would strongly impact oxygen concentrations of the BoB's low oxygen intermediate waters. Assuming decreasing nitrate concentrations and concurrent decreasing biomass production, export and respiration, oxygen concentrations within the oxygen minimum zone would not be expected to further decrease, an effect which would be enhanced by stronger stratification as a result of future warming. Therefore, given a decrease in primary production, the BoB may not be at a tipping point for becoming anoxic, unless external nutrient inputs increase. The role of the Bay of Bengal for primary production in the global Ocean -a historical perspectiveMarine primary producers contribute around 50% to global net primary production (Behrenfeld et al. 2001), leading to a carbon flux from the atmosphere into the ocean of 45-50 Tg C per year (Longhurst et al. 1995). Changes in ocean primary

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Trichodesmium blooms and warm-core ocean surface features in the Arabian Sea and the Bay of Bengal

Cited by 35 publications

References 67 publications

Data‐Driven Modeling of the Distribution of Diazotrophs in the Global Ocean

Data‐Driven Modeling of the Distribution of Diazotrophs in the Global Ocean

Assembly Processes and Co-occurrence Patterns of Abundant and Rare Bacterial Community in the Eastern Indian Ocean

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