Sources of iron and phosphate affect the distribution of diazotrophs in the North Atlantic

Ratten, Jenni-Marie; LaRoche, Julie; Desai, Dhwani; Shelley, Rachel; Landing, William M.; Boyle, Ed; Cutter, Gregory A.; Langlois, Rebecca

doi:10.1016/j.dsr2.2014.11.012

Cited by 35 publications

(41 citation statements)

References 72 publications

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“…Within the NA subtropical gyre, UCYN-A and Trichodesmium are the most abundant phylotypes (Figure 3), although they appear to be spatially segregated Agawin et al, 2014;Ratten et al, 2014). While UCYN occupy a wide latitudinal and longitudinal range ( Figures 3C,D), Trichodesmium is constrained to <30 • N in the NWA, with the exception of the data reported by Mulholland et al on the US East Coast (Mulholland et al, 2012, Figure 3A).…”

Section: Nutrient and Trace Metal Controlsmentioning

confidence: 43%

“…Finally, this group was found in high abundances along the East Coast of the US where it occurred at high dissolved inorganic nitrogen concentrations and comparatively low temperatures (Mulholland et al, 2012). Relatively high abundances of DDAs have been also reported off the eastern US coast, which could be due to actual in situ growth or as a result of transport from Amazon River plume affected waters along the Gulf Stream (Ratten et al, 2014).…”

Section: Nutrient and Trace Metal Controlsmentioning

confidence: 94%

“…Despite this great supply, the potential bioavailability of the iron deposited with dust is not well-understood (Mahowald et al, 2009). Significant correlations between dissolved iron concentrations, dust deposition rates (or dust deposition proxies like aerosol optical depth at 550 nm) and N 2 fixation rates or diazotroph phylotypes abundance have been recurrently reported in the NA (e.g., Moore et al, 2009;Fernández et al, 2010;Benavides et al, 2013d;Ratten et al, 2014). In addition, it is now clear that the shifts in the geographical extent of coverage of the intertropical convergence zone (ITCZ) controls iron inputs and hence N 2 fixation activity in the tropical and subtropical Atlantic (Schlosser et al, 2013).…”

Section: Responses To Atmospheric Dust Inputsmentioning

confidence: 99%

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Five decades of N2 fixation research in the North Atlantic Ocean

Benavides

Voß

2015

Front. Mar. Sci.

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Dinitrogen (N 2 ) fixation (the reduction of atmospheric N 2 to ammonium by specialized prokaryotic microbes), represents an important input of fixed nitrogen and contributes significantly to primary productivity in the oceans. Marine N 2 fixation was discovered in the North Atlantic Ocean (NA) in the 1960s. Ever since, the NA has been subject to numerous studies that have looked into the diversity and abundance of N 2 -fixing microbes (diazotrophs), the spatial and temporal variability of N 2 fixation rates, and the range of physical and chemical variables that control them. The NA provides 10-25% of the globally fixed N 2 , ranking as the third basin with the largest N 2 fixation inputs in the world's oceans. This basin suffers a chronic depletion in phosphorus availability, more aeolian dust deposition than any other basin in the world's oceans, and significant nutrient inputs from important rivers like the Amazon and the Congo. These characteristics make it unique in comparison with other oceanic basins. After five decades of intensive research, here we present a comprehensive review of our current understanding of diazotrophic activity in the NA from both a geochemical and biological perspective. We discuss the advantages and disadvantages of current methods, future perspectives, and questions which remain to be answered.

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Section: Nutrient and Trace Metal Controlsmentioning

confidence: 43%

Section: Nutrient and Trace Metal Controlsmentioning

confidence: 94%

Section: Responses To Atmospheric Dust Inputsmentioning

confidence: 99%

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Five decades of N2 fixation research in the North Atlantic Ocean

Benavides

Voß

2015

Front. Mar. Sci.

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“…In the temperate NE American coast, Mulholland et al (2012) showed that UCYN-A was the most abundant diazotroph, reaching 3.5 × 10 7 nifH copies L −1 , among the highest abundances ever observed. Several studies performed in the North Atlantic reported that, after Trichodesmium, UCYN-A is the most abundant diazotrophic phylotype (Benavides and Voss, 2015;Ratten et al, 2015;Benavides et al, 2016). Even though it extends along a wide latitudinal and longitudinal range, it dominates mainly the eastern basin, where iron inputs by Saharan dust are higher (Benavides et al, 2013), which favors its growth and N 2 -fixing activity (Krupke et al, 2015).…”

Section: Playersmentioning

confidence: 99%

Biological N2 Fixation in the Upwelling Region off NW Iberia: Magnitude, Relevance, and Players

et al. 2017

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The classical paradigm about marine N 2 fixation establishes that this process is mainly constrained to nitrogen-poor tropical and subtropical regions, and sustained by the colonial cyanobacterium Trichodesmium spp. and diatom-diazotroph symbiosis. However, the application of molecular techniques allowed determining a high phylogenic diversity and wide distribution of marine diazotrophs, which extends the range of ocean environments where biological N 2 fixation may be relevant. Between February 2014 and December 2015, we carried out 10 one-day samplings in the upwelling system off NW Iberia in order to: (1) investigate the seasonal variability in the magnitude of N 2 fixation, (2) determine its biogeochemical role as a mechanism of new nitrogen supply, and (3) quantify the main diazotrophs in the region under contrasting hydrographic regimes. Our results indicate that the magnitude of N 2 fixation in this region was relatively low (0.001 ± 0.002 -0.095 ± 0.024 µmol N m −3 d −1 ), comparable to the lower-end of rates described for the subtropical NE Atlantic. Maximum rates were observed at the surface during both upwelling and relaxation conditions. The comparison with nitrate diffusive fluxes revealed the minor role of N 2 fixation (<2%) as a mechanism of new nitrogen supply into the euphotic layer. Small diazotrophs (<10 µm) were responsible for all N 2 fixation activity detected in the region. Quantitative PCR targeting the nifH gene revealed the highest abundances of two sublineages of Candidatus Atelocyanobacterium thalassa or UCYN-A (UCYN-A1 and UCYN-A2), mainly at surface waters during upwelling and relaxation conditions, and of Gammaproteobacteria γ-24774A11 at deep waters during downwelling. Maximum abundance for the three groups were up to 6.7 × 10 2 , 1.5 × 10 3 , and 2.4 × 10 4 nifH copies L −1 , respectively. Our findings demonstrate measurable N 2 fixation activity and presence of diazotrophs throughout the year in a nitrogen-rich temperate region.

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“…Thus, the stoichiometry of the nutrient deposition and the stoichiometric nutritional demands of different plankton species modify the impacts of nutrient deposition on marine carbon fluxes [175•, 187]. Planktonic organisms will respond differentially to the atmospheric deposition of nutrients (and toxins) impacting plankton community structure and the efficiency of carbon export [141,170,188,189]. Recent estimates suggest an average of 0.07 PgC/year (±100%) draw down due to soluble iron deposition increases over the twentieth century [41].…”

Section: Marine Ecosystemsmentioning

confidence: 99%

Aerosol Deposition Impacts on Land and Ocean Carbon Cycles

Mahowald

Scanza

Brahney

et al. 2017

Curr Clim Change Rep

127

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Purpose of Review Atmospheric aerosol deposition is an important source of nutrients and pollution to many continental and marine ecosystems. Humans have heavily perturbed the cycles of several important aerosol species, potentially affecting terrestrial and marine carbon budgets and consequently climate. The most ecologically important aerosol elements impacted by humans are nitrogen, sulfur, iron, phosphorus, and base cations. Here, we review the latest research on the modification of the atmospheric cycles of these aerosols and their resulting effects on continental and marine ecosystems. Recent Findings Recent studies have improved our understanding of how humans have perturbed atmospheric aerosol cycles and how they may continue to evolve in the future. Research in both aquatic and terrestrial environments has highlighted the role of atmospheric deposition as a nutrient subsidy, with effects on ecosystem productivity. These studies further emphasize the importance of local biogeochemical conditions and biota species composition to the regional responses to aerosol deposition. Summary The size of the impact of anthropogenic aerosol deposition on the carbon cycle and the resulting climate forcing is at present not well understood. It is estimated that increases in nutrient subsidies from atmospheric deposition across all ecosystems are causing an increase in carbon dioxide uptake between 0.2 and 1.5 PgC/year. As aerosol emissions from industrial sources are reduced to improve air quality, these enhancements in carbon uptake may be reduced in the future leading to reduced carbon dioxide emission offsets. However, large uncertainties remain, not only because of limited information on how humans have modified and will modify aerosol emissions, but also because of a lack of quantitative understanding of how aerosol deposition impacts carbon cycling in many ecosystems.

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Sources of iron and phosphate affect the distribution of diazotrophs in the North Atlantic

Cited by 35 publications

References 72 publications

Five decades of N2 fixation research in the North Atlantic Ocean

Five decades of N2 fixation research in the North Atlantic Ocean

Biological N2 Fixation in the Upwelling Region off NW Iberia: Magnitude, Relevance, and Players

Aerosol Deposition Impacts on Land and Ocean Carbon Cycles

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