Impacts of Atmospheric Anthropogenic Nitrogen on the Open Ocean

Duce, Robert A.; LaRoche, Julie; Altieri, Katye E.; Arrigo, Kevin R.; Baker, Alex R.; Capone, Douglas G.; Cornell, Sarah; Dentener, Frank; Galloway, James N.; Ganeshram, Raja S.; Geider, Richard J.; Jickells, Tim; Kuypers, M. M.; Langlois, Rebecca; Liss, Peter S.; Liu, S. M.; Middelburg, Jack J.; Moore, C. Mark; Ničković, Slobodan; Oschlies, Andreas; Pedersen, T. F.; Prospero, Joseph M.; Schlitzer, Reiner; Seitzinger, Sybil P.; Sørensen, L.L.; Uematsu, Mitsuo; Ulloa, Osvaldo; Voß, Maren; Ward, Bess B.; Zamora, Lauren

doi:10.1126/science.1150369

Cited by 996 publications

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“…These fluxes are of comparable magnitude (Table 1) but differ in their geographical distribution. Anthropogenic perturbations to both supply routes have increased the external supply of nutrient elements to the ocean (Table 1) 12,[76][77][78][79] . Anthropogenic fixed nitrogen sources are comparable to that derived from biospheric nitrogen fixation 12,49 , leading to increased fluvial fluxes of nitrogen to the ocean 49 .…”

Section: Nature Geoscience Doi: 101038/ngeo1765mentioning

confidence: 99%

“…Anthropogenic perturbations to both supply routes have increased the external supply of nutrient elements to the ocean (Table 1) 12,[76][77][78][79] . Anthropogenic fixed nitrogen sources are comparable to that derived from biospheric nitrogen fixation 12,49 , leading to increased fluvial fluxes of nitrogen to the ocean 49 . Riverine phosphorus fluxes have also increased by 50-300% over preindustrial levels and are expected to track future global population increases, unless declining mineral phosphorus reserves offset such changes 80 .…”

Section: Nature Geoscience Doi: 101038/ngeo1765mentioning

confidence: 99%

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Processes and patterns of oceanic nutrient limitation

et al. 2013

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Microbial activity is a fundamental component of oceanic nutrient cycles. Photosynthetic microbes, collectively termed phytoplankton, are responsible for the vast majority of primary production in marine waters. The availability of nutrients in the upper ocean frequently limits the activity and abundance of these organisms. Experimental data have revealed two broad regimes of phytoplankton nutrient limitation in the modern upper ocean. Nitrogen availability tends to limit productivity throughout much of the surface low-latitude ocean, where the supply of nutrients from the subsurface is relatively slow. In contrast, iron often limits productivity where subsurface nutrient supply is enhanced, including within the main oceanic upwelling regions of the Southern Ocean and the eastern equatorial Pacific. Phosphorus, vitamins and micronutrients other than iron may also (co-)limit marine phytoplankton. The spatial patterns and importance of co-limitation, however, remain unclear. Variability in the stoichiometries of nutrient supply and biological demand are key determinants of oceanic nutrient limitation. Deciphering the mechanisms that underpin this variability, and the consequences for marine microbes, will be a challenge. But such knowledge will be crucial for accurately predicting the consequences of ongoing anthropogenic perturbations to oceanic nutrient biogeochemistry

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Section: Nature Geoscience Doi: 101038/ngeo1765mentioning

confidence: 99%

Section: Nature Geoscience Doi: 101038/ngeo1765mentioning

confidence: 99%

Processes and patterns of oceanic nutrient limitation

et al. 2013

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“…Conversely, anthropogenic increases in atmospheric deposition of nitrogen (Duce et al, 2008) may alleviate the ultra-oligotrophic conditions of the SPG and shift the heterotrophic diazotrophic community towards an autotrophic one dominated by, for example, Trichodesmium, such as in the North Pacific. Anthropogenic atmospheric nitrogen deposition has already affected other gyre systems like the Atlantic (Duce et al, 2008), which might also have been characterized by heterotrophic diazotrophs in the not so distant past. The SPG may serve as one of the last, and perhaps disappearing, oceanic regions to explore the function of ultra-oligotrophic microbial communities.…”

Section: Functioning Of a Heterotrophic Diazotrophic Communitymentioning

confidence: 99%

Heterotrophic organisms dominate nitrogen fixation in the South Pacific Gyre

et al. 2011

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Oceanic subtropical gyres are considered biological deserts because of the extremely low availability of nutrients and thus minimum productivities. The major source of nutrient nitrogen in these ecosystems is N 2 -fixation. The South Pacific Gyre (SPG) is the largest ocean gyre in the world, but measurements of N 2 -fixation therein, or identification of microorganisms involved, are scarce. In the 2006/2007 austral summer, we investigated nitrogen and carbon assimilation at 11 stations throughout the SPG. In the ultra-oligotrophic waters of the SPG, the chlorophyll maxima reached as deep as 200 m. Surface primary production seemed limited by nitrogen, as dissolved inorganic carbon uptake was stimulated upon additions of 15 N-labeled ammonium and leucine in our incubation experiments. N 2 -fixation was detectable throughout the upper 200 m at most stations, with rates ranging from 0.001 to 0.19 nM N h À1 . N 2 -fixation in the SPG may account for the production of 8-20% of global oceanic new nitrogen. Interestingly, comparable 15 N 2 -fixation rates were measured under light and dark conditions. Meanwhile, phylogenetic analyses for the functional gene biomarker nifH and its transcripts could not detect any common photoautotrophic diazotrophs, such as, Trichodesmium, but a prevalence of c-proteobacteria and the unicellular photoheterotrophic Group A cyanobacteria. The dominance of these likely heterotrophic diazotrophs was further verified by quantitative PCR. Hence, our combined results show that the ultra-oligotrophic SPG harbors a hitherto unknown heterotrophic diazotrophic community, clearly distinct from other oceanic gyres previously visited.

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“…Therefore, even though it is a relatively small source of P compared to other sources [Okin et al, 2011], atmospheric P can have a large impact on long-term nutrient limitation patterns if its relationship to new, nonrecycled, nitrogen (N) changes as it is currently doing. Over the past 150 years, the deposition of N compounds is estimated to have doubled [Duce et al, 2008], while the deposition of P species has remained relatively steady [Baker et al, 2003;Mahowald et al, 2008]. Consequently, recent modeling studies predict an atmospheric deposition-driven increase in P depletion in surface waters of some ocean regions relative to preindustrial times [Kanakidou et al, 2012;Kim et al, 2011;Krishnamurthy et al, 2007Krishnamurthy et al, , 2009Zamora et al, 2010].…”

Section: Introductionmentioning

confidence: 99%

Atmospheric P deposition to the subtropical North Atlantic: sources, properties, and relationship to N deposition

et al. 2013

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[1] Biogeochemical studies show that the surface waters of the subtropical North Atlantic are highly phosphorus (P) stressed. Human activity may exacerbate phosphorus stress by enhancing atmospheric nitrogen (N) deposition and raising N/P ratios in deposition. However, the magnitude of this effect is unclear, in part, because atmospherically deposited phosphorus sources are not well known, particularly the contribution from organic phosphorus. Here we report measurements of phosphorus in aerosols and wet deposition at Miami and Barbados. African dust is the major aerosol P source at both Miami and Barbados, containing~880 ppm total phosphorus and~70 ppm soluble reactive phosphorus (SRP). Organic compounds contribute, on average, 28%-44% of soluble phosphorus in precipitation. Because of dust transport seasonality, phosphorus inputs to the North Atlantic are expected to be highly variable with 2-10 times more P deposition during summer than winter. Pollution is also an important contributor to total and soluble phosphorus in Miami aerosols and deposition. Estimated SRP deposition in Barbados and Miami is 0.21 and 0.13 mmol m À2 d À1 phosphorus, respectively. Inorganic nitrogen in excess of Redfield ratio expectations in deposition was very different between the sites, totaling 21-30 and 127-132 mmol m À2 d À1 nitrogen in Barbados and Miami, respectively; the high deposition rates at Miami are linked to pollutants. Including soluble organic nitrogen and phosphorus halved the estimates of excess nitrogen in Barbados wet deposition. Thus, the organic phosphorus fraction is important in the assessment of the magnitude of biogeochemical change of the North Atlantic caused by atmospheric deposition.Citation: Zamora, L. M., J. M. Prospero, D. A. Hansell, and J. M. Trapp (2013), Atmospheric P deposition to the subtropical North Atlantic: sources, properties, and relationship to N deposition,

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Impacts of Atmospheric Anthropogenic Nitrogen on the Open Ocean

Cited by 996 publications

References 35 publications

Processes and patterns of oceanic nutrient limitation

Processes and patterns of oceanic nutrient limitation

Heterotrophic organisms dominate nitrogen fixation in the South Pacific Gyre

Atmospheric P deposition to the subtropical North Atlantic: sources, properties, and relationship to N deposition

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