Dinitrogen fixation in the world’s oceans

Karl, David M.; Michaels, Anthony F.; Bergman, Birgitta; Capone, D G; Carpenter, E. J.; Letelier, Ricardo M.; Lipschultz, Fredric; Paerl, Hans W.; Sigman, Daniel M.; Stal, Lucas J.

doi:10.1007/978-94-017-3405-9_2

Cited by 353 publications

(473 citation statements)

References 181 publications

(162 reference statements)

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“…A growing consensus has developed, however, that N fixation in marine systems, including estuaries, coastal seas, and also oceanic waters, likely is regulated by complex interactions of chemical, biotic, and physical factors (Paerl and Zehr 2000;Karl et al 2002;Marino et al 2002). Similarly, the controls on N fixation in terrestrial ecosystems probably involve a complex set of interactions (Vitousek et al 2002).…”

Section: Planktonic Nitrogen Fixationmentioning

confidence: 99%

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Howarth

Marino

2006

Limnology & Oceanography

1,194

733

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The first special volume of Limnology and Oceanography, published in 1972, focused on whether phosphorus (P) or carbon (C) is the major agent causing eutrophication in aquatic ecosystems. Only slight mention was made that estuaries may behave differently from lakes and that nitrogen (N) may cause eutrophication in estuaries. In the following decade, an understanding of eutrophication in estuaries proceeded in relative isolation from the community of scientists studying lakes. National water quality policy in the United States was directed almost solely toward P control for both lakes and estuaries, and similarly, European nations tended to focus on P control in lakes. Although bioassay data indicated N control of eutrophication in estuaries as early as the 1970s, this body of knowledge was treated with skepticism by many freshwater scientists and water-quality managers, because bioassay data in lakes often did not properly indicate the importance of P relative to C in those ecosystems. Hence, the bioassay data in estuaries had little influence on water-quality management. Over the past two decades, a strong consensus has evolved among the scientific community that N is the primary cause of eutrophication in many coastal ecosystems. The development of this consensus was based in part on data from whole-ecosystem studies and on a growing body of evidence that presented convincing mechanistic reasons why the controls of eutrophication in lakes and coastal marine ecosystems may differ. Even though N is probably the major cause of eutrophication in most coastal systems in the temperate zone, optimal management of coastal eutrophication suggests controlling both N and P, in part because P can limit primary production in some systems. In addition, excess P in estuaries can interact with the availability of N and silica (Si) to adversely affect ecological structure. Reduction of P to upstream freshwater ecosystems can also benefit coastal marine ecosystems through mechanisms such as increased Si fluxes.

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Section: Planktonic Nitrogen Fixationmentioning

confidence: 99%

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Howarth

Marino

2006

Limnology & Oceanography

1,194

733

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“…The export of carbon by the biological pump is conventionally regarded to be constrained by the nitrogen input, which is believed to set an upper limit to the organic carbon export equal to the product of the C/N ratio in the export organic carbon and the nitrogen supplied to the biogenic layer (Ducklow 1995;Williams 1995;Field et al 1998). The nitrogen input to the photic zone of the ocean is mainly derived from the internal supply of nitrate through vertical mixing, estimated at ∼50 Tmol N a −1 in subtropical waters (Jenkins and Wallace 1992;Lewis 2002), atmospheric inputs (Ducklow 1995;Williams 1995;Field et al 1998;Luz and Barkan 2000), estimated at about 10 Tmol N a −1 (Longhurst et al 1995) and nitrogen fixation for which there is little consensus on the global rate (7-14 Tmol N a −1 ; Karl et al 2002). The assumption that this net production equals the net carbon export by the biological pump is, in turn, based on the assumption that the carbon and nitrogen transport in the upward inorganic and the downward organic fluxes are in similar stoichiometric balance, but the latter assumption is unsupported by current data.…”

Section: Overall Rates Of Export Of Organic Carbon From the Photic Layermentioning

confidence: 99%

Respiration in the mesopelagic and bathypelagic zones of the oceans

Arı́stegui¹,

Agustı́²,

Middelburg³

et al. 2005

Respiration in Aquatic Ecosystems

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OutlineIn this chapter the mechanisms of transport and remineralization of organic matter in the dark water-column and sediments of the oceans are reviewed. We compare the different approaches to estimate respiration rates, and discuss the discrepancies obtained by the different methodologies. Finally, a respiratory carbon budget is produced for the dark ocean, which includes vertical and lateral fluxes of organic matter. In spite of the uncertainties inherent in the different approaches to estimate carbon fluxes and oxygen consumption in the dark ocean, estimates vary only by a factor of 1.5. Overall, direct measurements of respiration, as well as indirect approaches, converge to suggest a total dark ocean respiration of 1.5-1.7 Pmol C a −1 . Carbon mass balances in the dark ocean suggest that the dark ocean receives 1.5-1.6 Pmol C a −1 , similar to the estimated respiration, of which >70% is in the form of sinking particles. Almost all the organic matter (∼92%) is remineralized in the water column, the burial in sediments accounts for <1%. Mesopelagic (150-1000 m) respiration accounts for ∼70% of dark ocean respiration, with average integrated rates of 3-4 mol C m −2 a −1 , 6-8 times greater than in the bathypelagic zone (∼0.5 mol C m −2 a −1 ). The results presented here renders respiration in the dark ocean a major component of the carbon flux in the biosphere, and should promote research in the dark ocean, with the aim of better constraining the role of the biological pump in the removal and storage of atmospheric carbon dioxide.

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“…Biological nitrogen (N 2 ) fixation is a major source of nitrogen in the oligotrophic oceans (Capone, 2000;Carpenter, 1983;Karl et al, 2002). N 2 fixation by unicellular cyanobacteria, including Crocosphaera watsonii, can account for a large fraction (450%) of total N 2 fixation in oligotrophic waters Montoya et al, 2004;Zehr et al, 2007b).…”

Section: Introductionmentioning

confidence: 99%

In situ transcriptomic analysis of the globally important keystone N2-fixing taxon Crocosphaera watsonii

et al. 2009

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The diazotrophic cyanobacterium Crocosphaera watsonii supplies fixed nitrogen (N) to N-depleted surface waters of the tropical oceans, but the factors that determine its distribution and contribution to global N 2 fixation are not well constrained for natural populations. Despite the heterogeneity of the marine environment, the genome of C. watsonii is highly conserved in nucleotide sequence in contrast to sympatric planktonic cyanobacteria. We applied a whole assemblage shotgun transcript sequencing approach to samples collected from a bloom of C. watsonii observed in the South Pacific to understand the genomic mechanisms that may lead to high population densities. We obtained 999 C. watsonii transcript reads from two metatranscriptomes prepared from mixed assemblage RNA collected in the day and at night. The C. watsonii population had unexpectedly high transcription of hypothetical protein genes (31% of protein-encoding genes) and transposases (12%). Furthermore, genes were expressed that are necessary for living in the oligotrophic ocean, including the nitrogenase cluster and the iron-stress-induced protein A (isiA) that functions to protect photosystem I from high-light-induced damage. C. watsonii transcripts retrieved from metatranscriptomes at other locations in the southwest Pacific Ocean, station ALOHA and the equatorial Atlantic Ocean were similar in composition to those recovered in the enriched population. Quantitative PCR and quantitative reverse transcriptase PCR were used to confirm the high expression of these genes within the bloom, but transcription patterns varied at shallower and deeper horizons. These data represent the first transcript study of a rare individual microorganism in situ and provide insight into the mechanisms of genome diversification and the ecophysiology of natural populations of keystone organisms that are important in global nitrogen cycling.

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Dinitrogen fixation in the world’s oceans

Cited by 353 publications

References 181 publications

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Respiration in the mesopelagic and bathypelagic zones of the oceans

In situ transcriptomic analysis of the globally important keystone N2-fixing taxon Crocosphaera watsonii

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