Bridging the Spatiotemporal Gap in Diazotroph Activity and Diversity With High-Resolution Measurements

Benavides, Mar; Robidart, Julie

doi:10.3389/fmars.2020.568876

Cited by 13 publications

(5 citation statements)

References 109 publications

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“…Our findings suggest that N 2 fixation may be underestimated not only in the Arctic, but in other upwelling coastal systems where UCYN-A thrives. More widespread application of high-resolution approaches to studying diazotrophy (Benavides and Robidart, 2020) are necessary to discern the impact of ocean physics on N 2 fixation. Doing so may be particularly important in the Arctic Ocean, where the number and intensity of upwelling events is increasing (Pickart et al, 2013)-a trend that may be exacerbated by warming-induced ice retreat.…”

Section: Discussionmentioning

confidence: 99%

Coastal upwelling enhances abundance of a symbiotic diazotroph (UCYN-A) and its haptophyte host in the Arctic Ocean

et al. 2022

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The apparently obligate symbiosis between the diazotroph Candidatus Atelocyanobacterium thalassa (UCYN-A) and its haptophyte host, Braarudosphaera bigelowii, has recently been found to fix dinitrogen (N2) in polar waters at rates (per cell) comparable to those observed in the tropical/subtropical oligotrophic ocean basins. This study presents the novel observation that this symbiosis increased in abundance during a wind-driven upwelling event along the Alaskan Beaufort shelfbreak. As upwelling relaxed, the relative abundance of B. bigelowii among eukaryotic phytoplankton increased most significantly in waters over the upper slope. As the host’s nitrogen demands are believed to be supplied primarily by UCYN-A, this response suggests that upwelling may enhance N2 fixation as displaced coastal waters are advected offshore, potentially extending the duration of upwelling-induced phytoplankton blooms. Given that such events are projected to increase in intensity and number with ocean warming, upwelling-driven N2 fixation as a feedback on climate merits investigation.

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Section: Discussionmentioning

confidence: 99%

Coastal upwelling enhances abundance of a symbiotic diazotroph (UCYN-A) and its haptophyte host in the Arctic Ocean

et al. 2022

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“…Few studies have focused on particle fluxes that occur during the interaction between nitrogen fixation and a cyclonic eddy. Previous work has shown that nitrogen fixation rates may differ spatially, especially between the EC and EE (Löscher et al 2016), as well as temporally; upon eddy formation, N 2 fixer abundance is typically reduced, with occasional cyanobacterial blooms observed during the eddy's decay stage (Doblin et al 2016; Benavides and Robidart 2020). Here, lower temperatures and higher nutrient concentrations associated with eddy passage at Station ALOHA (e.g., Huang and Xu 2018), likely reduced diazotroph abundance, which is often associated with higher temperatures and lower nutrients (Karl et al 2002).…”

Section: Discussionmentioning

confidence: 99%

Cyclonic eddies modulate temporal and spatial decoupling of particulate carbon, nitrogen, and biogenic silica export in the North Pacific Subtropical Gyre

Zhou

Benítez-Nelson

Huang

et al. 2021

Limnology & Oceanography

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Mesoscale eddies may enhance nutrient injection into the photic zone and ultimately the magnitude and composition of particle export to depth. Using satellite altimetry, we identified 38 cyclonic eddies that passed in close proximity to the Hawaii Ocean Time‐series (HOT) Station ALOHA, located in the North Pacific Subtropical Gyre, from 1993 to 2018. Particulate carbon (C), nitrogen (N), and biogenic silica (Si) export rates, measured using free floating sediment traps deployed at 150 m as part of HOT, were then associated with either the eddy core or edge based on distance to the eddy center and time of eddy evolution. Elemental fluxes varied significantly within and among individual eddies depending on season and eddy age. Spatially, biogenic Si fluxes were enhanced relative to particulate C and N fluxes at both the cores and edges, with temporally highest particulate C, N and biogenic Si fluxes occurring during the mature stage (3–8 weeks). On average, biogenic Si fluxes were 200 ± 80% (30–270% increase) higher relative to non‐eddy and during non‐bloom periods, with modest enhanced particulate C (10–30% increase) and N (10–20% increase) fluxes. In contrast, during the bloom season (July and August), elemental fluxes were all reduced by 20% relative to non‐eddy references, suggesting that cyclonic eddies depress export during the bloom period. Our results indicate that cyclonic eddies not only increase, but differentially impact the sinking export of critical biological elements, thereby contributing to long term ecological changes in foodwebs that rely on silica as well as carbon for growth.

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“…Although anticyclonic eddies have generally been considered to benefit autotrophic diazotrophs by inhibiting vertical DIN input from deep waters (Liu et al, 2020;Fong et al, 2008;Church et al, 2009), a class of NCDs, Gammaproteobacteria, has been found to dominate diazotrophic communities inside cyclonic eddies in the South China Sea (Zhang et al, 2011;Liu et al, 2020). Different types of mesoscale eddies may have discrepancies in impacting the ecophysiology of NCDs and their autotrophic counterparts (Benavides and Robidart, 2020). Langlois et al (2015) analyzed the distribution of the Gamma A phylotype in the Pacific and Atlantic oceans and suggested that Gamma A prefers warm and oligotrophic surface oceans.…”

Section: Introductionmentioning

confidence: 99%

Controlling factors on the global distribution of a representative marine non-cyanobacterial diazotroph phylotype (Gamma A)

Shao

Luo²

2022

Biogeosciences

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Abstract. Non-cyanobacterial diazotrophs may be contributors to global marine N2 fixation, although the factors controlling their distribution are unclear. Here, we explored what controls the distribution of the most sampled non-cyanobacterial diazotroph phylotype, Gamma A, in the global ocean. First, we represented Gamma A abundance by its nifH quantitative polymerase chain reaction (qPCR) copies reported in the literature and analyzed its relationship to climatological biological and environmental conditions. There was a positive correlation between the Gamma A abundance and local net primary production (NPP), and the maximal observed Gamma A abundance increased with NPP and became saturated when NPP reached ∼ 400 mg C m−2 d−1. Additionally, an analysis using a multivariate generalized additive model (GAM) revealed that the Gamma A abundance increased with light intensity but decreased with increasing iron concentration. The GAM also showed a weak but significant positive relationship between Gamma A abundance and silicate concentration, as well as a substantial elevation of Gamma A abundance when the nitrate concentration was very high (≳ 10 µM). Using the GAM, these climatological factors together explained 43 % of the variance in the Gamma A abundance. Second, in addition to the climatological background, we found that Gamma A abundance was elevated in mesoscale cyclonic eddies in high-productivity (climatological NPP > 400 mg m−2 d−1) regions, implying that Gamma A can respond to mesoscale features and benefit from nutrient inputs. Overall, our results suggest that Gamma A tends to inhabit ocean environments with high productivity and low iron concentrations and therefore provide insight into the niche differentiation of Gamma A from cyanobacterial diazotrophs, which are generally most active in oligotrophic ocean regions and need a sufficient iron supply, although both groups prefer well-lit surface waters. More sampling on Gamma A and other non-cyanobacterial diazotroph phylotypes is needed to reveal the controlling mechanisms of heterotrophic N2 fixation in the ocean.

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Bridging the Spatiotemporal Gap in Diazotroph Activity and Diversity With High-Resolution Measurements

Cited by 13 publications

References 109 publications

Coastal upwelling enhances abundance of a symbiotic diazotroph (UCYN-A) and its haptophyte host in the Arctic Ocean

Coastal upwelling enhances abundance of a symbiotic diazotroph (UCYN-A) and its haptophyte host in the Arctic Ocean

Cyclonic eddies modulate temporal and spatial decoupling of particulate carbon, nitrogen, and biogenic silica export in the North Pacific Subtropical Gyre

Controlling factors on the global distribution of a representative marine non-cyanobacterial diazotroph phylotype (Gamma A)

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