Microbial ecology of the South Atlantic Subtropical Gyre: a state-of-the-art review of an understudied ocean region

Frazão, Luciana Rocha; Penninck, Silvana B.; Mychelazzo, Luan Sayeg; Vega, Gelaysi Moreno; Guimarães, Claudia Maria Duarte de Sá; Lopes, Rubens M.; Signori, Camila Negrão

doi:10.1590/2675-2824069.20026lrf

Cited by 7 publications

(7 citation statements)

References 115 publications

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“…Moreover, changes in the transport of SASG boundary currents might affect the redistribution of heat 147 , dissolved gases and biogeochemical tracers 148,149 , pollutants 150 , plastic debris 151,152 , nutrients 147 and alter species dispersal (such as in the case of eggs and larvae) 153 -affecting surface primary productivity 154 , altering the distribution of marine species 155,156 and impacting regional fisheries in meaningful ways 157,158 . As intensified western boundary currents transport more heat poleward, "tropicalisation" of marine communities is induced -meaning that warm-water species shift their distribution towards the poles in response to warming.…”

Section: Discussionmentioning

confidence: 99%

Weakened AMOC upper limb compensated by strengthened South Atlantic subtropical gyre circulation in CESM1-LE simulations

Marcello

Tonelli

Wainer

2023

Preprint

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<p><span>The upper limb of the Atlantic Meridional Overturning Circulation (AMOC) brings shallow interocean contributions to replenish the North Atlantic export of deepwaters. It is primarily formed in the southern South Atlantic where the converging entrainment of Pacific and Indian Ocean waters meet and incorporate into the South Atlantic subtropical gyre (SASG). Here, the human-induced response of AMOC and SASG near-surface pathways is illustrated according to CESM1 Large Ensemble simulations from 1920 to 2100, where future projections derive from the most aggressive (yet most realistic) scenario in assumed fossil fuel use and greenhouse gas emissions. In terms of flow redistribution, it is shown that the AMOC upper limb weakens not because less waters are being imported from the adjacent ocean basins &#8212; but because they are being mostly directed to recirculate in the southwestern portion of a distorted SASG, turning back southward after reaching the South Atlantic western boundary.</span></p>

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Section: Discussionmentioning

confidence: 99%

Weakened AMOC upper limb compensated by strengthened South Atlantic subtropical gyre circulation in CESM1-LE simulations

Marcello

Tonelli

Wainer

2023

Preprint

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“…Considering studies performed in the equatorial Pacific, it was revealed that there are minor seasonal influences but clear interannual patterns in picoplankton, mainly influenced by El Niño Southern Oscillation/ENSO events (Dandonneau et al, 2004), with a significant reduction of larger phytoplankton groups (Bidigare and Ondrusek, 1996). Picoplankton time-series studies in the equatorial Atlantic are scarce, especially near the Brazilian coast (Frazão et al, 2021). So far, time-series approaches have only Menezes et al been conducted in the south-southeast region with contrasting seasonal dynamics, including intrusions and high productivity events (Andrade et al, 2004;Moser et al, 2016;Bergo et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Temporal patterns of picoplankton abundance and metabolism on the western coast of the equatorial Atlantic Ocean

et al. 2023

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Ocean and Coastal ResearchPicoplankton are central global carbon (C) cycling players and often dominate the ocean plankton communities, especially in low latitudes. Therefore, evaluating picoplankton temporal dynamics is critical to understanding microbial stocks and C fluxes in tropical oceans. However, the lack of studies on low-latitude picoplankton communities translates into a common conception that there is an absence of seasonality. Herein, we studied the temporal variation in abundance (measured by flow cytometry), and carbon flux (taking bacterial production and respiration as proxies) of the picoplanktonic community for the first time, as well as their environmental drivers in a low-latitude (05° 59' 20.7″S 035° 05' 14.6″W) Atlantic coastal station. We performed monthly samplings between February 2013 and August 2016 in a novel microbial observatory -hereafter called the Equatorial Atlantic Microbial Observatory -established on the northeastern Brazilian Atlantic coast. Our results revealed stability in temporal dynamics of picoplankton, despite a considerable inter-annual variation, with some related to the El Niño (ENSO) event in 2015. However, weak environmental relationships found were not enough to explain the variation in picoplankton's abundance, which suggests that other factors such as biological interactions may lead to picoplankton abundance variation over time. Heterotrophic bacteria dominated picoplankton during the entire study period and between photosynthetic counterparts, and Synechococcus showed greater relative importance than picoeukaryotes. These results bring a novel perspective that picoplankton may exhibit more pronounced fluctuations in the tropical region when considering inter-annual intervals, and is increasing prokaryotic contribution to carbon cycling towards the equator.

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“…The deep sea, defined as the ocean lying below 200 m depth, is a highly connected environment; however, it remains undersampled, particularly in the southern hemisphere (Levin et al, 2019;Frazão et al, 2021). A recent review on microbial ecology in the ocean reported that there are only 38 studies in the ocean basins of the southern hemisphere, compared with 290 studies conducted in the North Atlantic Ocean (Frazão et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Contribution of chemoautotrophy and heterotrophy to the microbial carbon cycle in the Southwestern Atlantic Ocean

et al. 2022

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Dark carbon fixation (DCF) is a source of new and labile carbon in the deep ocean, while heterotrophic microbial production (HMP) promotes organic matter transfer through the microbial loop. Despite their ecological relevance, there is a scientific gap regarding the estimates of DCF and HMP in the Southwestern Atlantic Ocean. Thus, the aim of this study was to investigate the spatial distribution of DCF and HMP; their relevance to the ocean carbon cycle; their relationship with environmental parameters and amongst themselves on the upper slope of Santos Basin. The samples were collected at three different water depths and sediment layers aboard the R/V Alpha Crucis in November 2019. DCF and HMP rates were measured by 14 C-bicarbonate and 3 H-leucine incorporation, respectively, and incubated in the dark. In the water column, DCF rates varied from 1.51 x 10 1 to 3.24 x 10 2 µg C m -3 h -1 , which were one to two orders of magnitude lower than the HMP rates, from 1.26 x 10 2 to 1.48 x 10 4 µg C m -3 h -1 . In the sediments, the DCF ranged from 1.15 x 10 4 to 1.83 x 10 5 µg C m -3 h -1 , while HMP was one to four orders of magnitude lower, 3.22 x 10 1 to 1.56 x 10 3 µ gC m -3 h -1 . DCF rates were significantly higher in the sediments, due to a higher availability of energy sources than in the oligotrophic water above. The HMP had higher rates in the water column as it is deeply dependent on organic matter derived from photosynthesis. This is the first study to investigate DCF and HMP considering the water column and sediments of the Southwestern Atlantic Ocean, thus contributing to a better understanding of the microbial role in the marine carbon cycle and ecosystem functioning.

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Microbial ecology of the South Atlantic Subtropical Gyre: a state-of-the-art review of an understudied ocean region

Cited by 7 publications

References 115 publications

Weakened AMOC upper limb compensated by strengthened South Atlantic subtropical gyre circulation in CESM1-LE simulations

Weakened AMOC upper limb compensated by strengthened South Atlantic subtropical gyre circulation in CESM1-LE simulations

Temporal patterns of picoplankton abundance and metabolism on the western coast of the equatorial Atlantic Ocean

Contribution of chemoautotrophy and heterotrophy to the microbial carbon cycle in the Southwestern Atlantic Ocean

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