<?xml version="1.0" encoding="utf-8" standalone="no"?>
<!DOCTYPE article SYSTEM "http://www.biogeosciences.net/inc/bg/copernicus.dtd">
<article language="en">
	<journal>
		<journal_title>Biogeosciences</journal_title>
		<journal_url>www.biogeosciences.net</journal_url>
		<issn>1726-4170</issn>
		<eissn>1726-4189</eissn>
		<volume_number>5</volume_number>
		<issue_number>4</issue_number>
		<publication_year>2008</publication_year>
	</journal>
	<doi>10.5194/bg-5-1033-2008</doi>
	<article_url>http://www.biogeosciences.net/5/1033/2008/</article_url>
	<abstract_html>http://www.biogeosciences.net/5/1033/2008/bg-5-1033-2008.html</abstract_html>
	<fulltext_pdf>http://www.biogeosciences.net/5/1033/2008/bg-5-1033-2008.pdf</fulltext_pdf>
	<start_page>1033</start_page>
	<end_page>1041</end_page>
	<publication_date>2008-07-24</publication_date>
	<article_title content_type="html">Recent advances in the biogeochemistry of nitrogen in the ocean</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>S. W. A. Naqvi</name>
			<email>naqvi@nio.org</email>
		</author>
		<author numeration="2" affiliations="2">
			<name>M. Voss</name>
		</author>
		<author numeration="3" affiliations="3">
			<name>J. P. Montoya</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403 004, India</affiliation>
		<affiliation numeration="2" content_type="html">Leibniz Institute for Baltic Sea Research, Seestrasse 15, 18119 Rostock, Germany</affiliation>
		<affiliation numeration="3" content_type="html">School of Biology, Georgia Institute of Technology, Atlanta GA 30332, USA</affiliation>
	</affiliations>
	<abstract content_type="html">No abstract available.</abstract>
	<references>
		<reference numeration="1" content_type="text"> Altabet, M. A.: Constraints on oceanic N balance/imbalance from sedimentary $^15$N records, Biogeosciences, 4, 75–86, 2007. </reference>
		<reference numeration="2" content_type="text"> Altabet, M. A., François, R., Murray, D. W., and Prell, W. L.: Climate-related variations in denitrification in the Arabian Sea from sediment $^15$N/$^14$N ratios, Nature, 373, 506–509, 1995. </reference>
		<reference numeration="3" content_type="text"> Bange, H. W., Andreae, M. O., Lal, S., Law, C. S., Naqvi, S. W. A., Patra, P. K., Rixen, T., and Upstill-Goddard, R. C.: Nitrous oxide emissions from the Arabian Sea: A synthesis, Atmos. Chem. Phys., 1, 61–71, 2001. </reference>
		<reference numeration="4" content_type="text"> Bange, H. W.: New directions: The importance of oceanic nitrous oxide emissions, Atmos. Environ., 40, 198–199, 2006. </reference>
		<reference numeration="5" content_type="text"> Beman, J. M., Popp, B. N., and Francis, C. A.: Molecular and biogeochemical evidence for ammonia oxidation by marine Crenarchaeota in the Gulf of California, ISME J., 2, 429–441, 2008. </reference>
		<reference numeration="6" content_type="text"> Braker, G., Zhou, J. Z., Wu, L. Y., Devol, A. H., and Tiedje, J. M.: Nitrite reductase genes (nirK and nirS) as functional markers to investigate diversity of denitrifying bacteria in Pacific northwest marine sediment communities, Appl. Environ. Microbiol., 66, 2096–2104, 2000. </reference>
		<reference numeration="7" content_type="text"> Brandes, J. A., and Devol, A. H.: A global marine-fixed nitrogen isotopic budget: Implications for Holocene nitrogen cycling, Global Biogeochem. Cy., 16, 1120, doi:10.1029/2001GB001856, 2002. </reference>
		<reference numeration="8" content_type="text"> Brandes, J. A., Devol, A. H., and Deutsch, C.: New developments in the marine nitrogen cycle, Chem. Rev., 107, 577–589, 2007. </reference>
		<reference numeration="9" content_type="text"> Brandes, J. A., Devol, A. H., Yoshinari, T., Jayakumar, A., and Naqvi, S. W. A.: Isotopic composition of nitrate in the central Arabian Sea and eastern tropical North Pacific: A tracer for mixing and nitrogen cycles, Limnol. Oceanogr., 43, 1680–1689, 1998. </reference>
		<reference numeration="10" content_type="text"> Bonin, P. and Raymond, N.: Effects of oxygen on denitrification in marine sediments. Hydrobiologia, 207, 115–122, 1990. </reference>
		<reference numeration="11" content_type="text"> Breitbarth, E., Oschlies, A., and LaRoche, J.: Physiological constraints on the global distribution of \textitTrichodesmium – effect of temperature on diazotrophy, Biogeosciences, 4, 53–61, 2007. </reference>
		<reference numeration="12" content_type="text"> Bronk, D. A., See, J. H., Bradley, P., and Killberg, L.: DON as a source of bioavailable nitrogen for phytoplanton, Biogeosciences, 4, 283–296, 2007. </reference>
		<reference numeration="13" content_type="text"> Brunelle, B. G., Sigman, D. M., Cook, M. S., Keigwin, L. D., Haug, G. H., Plessen, B., Schettler, G., and Jaccard, S. L.: Evidence from diatom-bound nitrogen isotopes for subarctic Pacific stratification during the last ice age and a link to North Pacific denitrification changes, Paleoceanography, 22, PA1215, doi:10.1029/2005PA001205, 2007. </reference>
		<reference numeration="14" content_type="text"> Casciotti, K. L. and McIlvin, M. R.: Isotopic analyses of nitrate and nitrite from reference mixtures and application to Eastern Tropical North Pacific waters, Mar. Chem.,~107, 184-201, 2007. </reference>
		<reference numeration="15" content_type="text"> Castro-Gonzalez, M., Braker, G., Farias, L., and Ulloa, O.: Communities of nirS-type denitrifiers in the water column of the oxygen minimum zone in the eastern South Pacific, Environ. Microbiol., 7, 1298–1306, 2005. </reference>
		<reference numeration="16" content_type="text"> Chen, C. C., Gong, G. C., and Shiah, F. K.: Hypoxia in the East China Sea: One of the largest coastal low-oxygen areas in the world, Mar. Environ. Res., 64, 399–408, 2007 ~ </reference>
		<reference numeration="17" content_type="text"> Cline, J. D. and Richards, F. A.: Oxygen deficient conditions and nitrate reduction in the eastern tropical North Pacific Ocean, Limnol. Oceanogr., 17, 885–900, 1972. </reference>
		<reference numeration="18" content_type="text"> Codispoti, L. A. and Christensen, J. P.: Nitrification, denitrification and nitrous oxide cycling in the eastern tropical South Pacific Ocean, Mar. Chem., 16, 277–300, 1985. </reference>
		<reference numeration="19" content_type="text"> Codispoti, L. A., Brandes, J. A., Christensen, J. P., Devol, A. H., Naqvi, S. W. A., Paerl, H. W., and Yoshinari, T.: The oceanic fixed nitrogen and nitrous oxide budgets: Moving targets as we enter the anthropocene? Sci. Mar., 65, 85–105, 2001. </reference>
		<reference numeration="20" content_type="text"> Codispoti, L. A.: An oceanic fixed nitrogen sink exceeding 400 TgNa&lt;sup&gt;&amp;minus;1&lt;/sup&gt; vs the concept of homeostasis in the fixed-nitrogen inventory, Biogeosciences, 4, 233–253, 2007. </reference>
		<reference numeration="21" content_type="text"> Coles, V. J. and Hood, R. R.: Modeling the impact of iron and phosphorus limitations on nitrogen fixation in the Atlantic Ocean, Biogeosciences, 4, 455–479, 2007. </reference>
		<reference numeration="22" content_type="text"> Dalsgaard, T. and Thamdrup, B.: Factors controlling anaerobic ammonium oxidation with nitrite in marine sediments, Appl. Environ. Microbiol., 68, 3802–3808, 2002. </reference>
		<reference numeration="23" content_type="text"> Dalsgaard, T., Canfield, D. E., Petersen, J., Thamdrup, B., and Acuna-Gonzalez, J.: N&lt;sub&gt;2&lt;/sub&gt; production by the anammox reaction in the anoxic water column of Golfo Dulce, Costa Rica, Nature, 422, 602–608, 2003. </reference>
		<reference numeration="24" content_type="text"> Delmas, R. J., Ascencio, J. -M., and Legrand, M.: Polar ice evidence that atmospheric CO&lt;sub&gt;2&lt;/sub&gt; 20 000 yr BP was 50% of present, Nature, 284, 155–57, 1980. </reference>
		<reference numeration="25" content_type="text"> Deutsch, C., Sigman, D. M., Thunell, R. C., Meckler, A. N., and Haug, G. H.: Isotopic constraints on glacial/interglacial changes in the oceanic nitrogen budget, Global Biogeochem. Cy., 18, 4013, doi:10.1029/2003GB002189, 2004. </reference>
		<reference numeration="26" content_type="text"> Deutsch, C., Sarmiento, J., Sigman D. M., Gruber, N., and Dunne, J.: Spatial coupling of nitrogen inputs and losses in the ocean, Nature, 445, 163-167, 2007. </reference>
		<reference numeration="27" content_type="text"> Devol, A. H.: Bacterial oxygen uptake kinetics as related to biological processes in the oxygen deficient zones of the oceans, Deep-Sea Res., 25, 137–146, 1978. </reference>
		<reference numeration="28" content_type="text"> Devol, A. H., Uhlenhopp, A. G., Naqvi, S. W. A., Brandes, J. A., Jayakumar, A., Naik, H., Gaurin, S., Codispoti, L. A., and Yoshinari, T.: Denitrification rates and excess nitrogen gas concentrations in the Arabian Sea oxygen deficient zone, Deep-Sea Res. I, 53, 1533–1547, 2006. </reference>
		<reference numeration="29" content_type="text"> Diaz, R. J.: Overview of hypoxia around the world, J. Environ. Qual., 30, 275-281, 2001. </reference>
		<reference numeration="30" content_type="text"> Emery, K. O., Orr, W. L., and Rittenberg, S. C.: Nutrient budgets in the ocean, in: Essays in Natural Sciences in Honor of Captain Allan Hancock, University of Southern California Press, Los Angeles, pp. 299-309, 1955. </reference>
		<reference numeration="31" content_type="text"> Falcon, L. I., Carpenter, E. J., Cipriano, F., Bergman, B., and Capone, D. G.: N&lt;sub&gt;2&lt;/sub&gt; fixation by unicellular bacterioplankton from the Atlantic and Pacific Oceans: Phylogeny and in situ rates, Appl. Environ. Microbiol., 70, 765–770, 2004. </reference>
		<reference numeration="32" content_type="text"> Falk, S., M. Hannig, M., Gliesche, C., Wardenga, R., Köster, M., Jürgens, K., and Braker, G.: nirS-containing denitrifier communities in the water column and sediment of the Baltic Sea, Biogeosciences, 4, 255–268, 2007. </reference>
		<reference numeration="33" content_type="text"> Falkowski, P. G.: Evolution of the nitrogen cycle and its influence on the biological sequestration of CO&lt;sub&gt;2&lt;/sub&gt; in the ocean, Nature, 387, 272–275, 1997. </reference>
		<reference numeration="34" content_type="text"> Fossing, H, Gallardo, V. A., Huttel, M., Nielsen, L. P., Schulz, H., Canfield, D. E., Forster, S., Glud, R. N., Gundersen, J. K., Kuver, J., Ramsing, N. B., Teske, A., Thamdrup, B., and Ulloa, O.: Concentration and transport of nitrate by the mat-forming sulphur bacterium \textitThioploca, Nature, 374, 713–715, 1995. </reference>
		<reference numeration="35" content_type="text"> Francis, C. A., Beman, J. M., and Kuypers, M. M. M.: New processes and players in the nitrogen cycle: the microbial ecology of anaerobic and archaeal ammonia oxidation, ISME J., 1, 19–27, 2007. </reference>
		<reference numeration="36" content_type="text"> Galloway, J. N., Dentener, F. J., Capone, D. G., Boyer, E. W., Howarth, R. W., Seitzinger, S. P., Asner, G. P., Cleveland, C. C., Green, P. A., Holland, E. A., Karl, D. M., Michaels, A. F., Porter, J. H., Townsend, A. R., and Vorosmarty, C. J.: Nitrogen cycles: past, present and future, Biogeochemistry, 70, 153–226, 2004. </reference>
		<reference numeration="37" content_type="text"> Ganeshram, R. S., Pedersen, T. F., Calvert, S. F., and Murray, J. W.: Large changes in oceanic nutrient inventories from glacial to interglacial periods, Nature, 376, 755–758, 1995. </reference>
		<reference numeration="38" content_type="text"> Gruber, N.: The dynamics of the marine nitrogen cycle and its influence on atmospheric CO&lt;sub&gt;2&lt;/sub&gt;, in: The Ocean Carbon Cycle and Climate, edited by: Follows, M. and Oguz, T., NATO ASI Series, Kluwer Academic, Dordrecht, 97–148, 2004. </reference>
		<reference numeration="39" content_type="text"> Gruber, N.: Interactive comment on &quot;An oceanic fixed nitrogen sink exceeding 400 TgNa&lt;sup&gt;&amp;minus;1&lt;/sup&gt; vs the concept of homeostasis in the fixed-nitrogen inventory&quot; by Codispoti, L. A., Biogeosciences Discuss., 3, S368–S374, 2006. </reference>
		<reference numeration="40" content_type="text"> Gruber, N., and Sarmiento, J. L.: Global patterns of marine nitrogen fixation and denitrification. Global Biogeochem. Cy., 11, 235-266, 1997. </reference>
		<reference numeration="41" content_type="text"> Hamersley, M. R., Lavik, G., Woebken, D., Rattray, J. E., Lam, P., Hopmans, E. C., Sinninghe Damsté, J. S., Krüger, S., Graco, M., Gutiérrez, D., and Kuypers, M. M. M.: Anaerobic ammonium oxidation in the Peruvian oxygen minimum zone, Limnol. Oceanogr. 52, 923–933, 2007. </reference>
		<reference numeration="42" content_type="text"> Jayakumar, D. A., Francis, C. A., Naqvi, S. W. A., and Ward, B. B.: Diversity of nitrite reductase genes (nirS) in the denitrifying water column of the coastal Arabian Sea, Aquat. Microb. Ecol., 34, 69–78, 2004. </reference>
		<reference numeration="43" content_type="text"> Jickels, T.: The role of air-sea exchange in the marine nitrogen cycle, Biogeosciences,~3,~271–280,~2006. </reference>
		<reference numeration="44" content_type="text"> Johnson, K. S., Coletti, L. J., and Chavez, F. P.: Diel nitrate cycles observed with in situ sensors predict monthly and annual new production, Deep-Sea Res. I, 53, 561–573, 2006. </reference>
		<reference numeration="45" content_type="text"> Körner, H., and Zumft, W. G.: Expression of denitrification enzymes in response to the dissolved oxygen level and respiratory substrate in continuous culture of \textitPseudomonas stutzeri, Appl. Environ. Microbiol., 55, 1670–1676, 1989. </reference>
		<reference numeration="46" content_type="text"> Kuypers, M. M. M., Sliekers, A. O., Lavik, G., Schmid, M., Jørgensen, B. B., Kuenen, J. G., Sinninghe Damsté, J. S., Strous, M., and Jetten M. S. M.: Anaerobic ammonium oxidation by anammox bacteria in the Black Sea, Nature, 422, 608–611, 2003. </reference>
		<reference numeration="47" content_type="text"> Kuypers, M. M. M., Lavik, G., Wöbken, D., Schmid, M., Fuchs, B. M., Amann, R., Jørgensen, B. B., and Jetten M. S. M.: Massive nitrogen loss from the Benguela upwelling system through anaerobic ammonium oxidation, Proc. Nat. Acad. Sci. USA, 102, 6478–6483, 2005. </reference>
		<reference numeration="48" content_type="text"> Lam, P., Jensen, M. M., Lavik, G., McGinnis, D. F., Muller, B., Schubert, C. J., Amann, R., Thamdrup, B., and Kuypers, M. M. M.: Linking crenarchaeal and bacterial nitrification to anammox in the Black Sea, Proc. Natl. Acad. Sci. USA, 104, 7104–7109, 2007. </reference>
		<reference numeration="49" content_type="text"> Luther, G. W., Sundby, B., Lewis, B. L., Brendel, P. J., and Silverberg, N.: Interactions of manganese with the nitrogen cycle: Alternative pathways to dinitrogen, Geochim. Cosmochim. Ac., 61, 4043–4052, 1997. </reference>
		<reference numeration="50" content_type="text"> McElroy, M. B.: Marine biological controls on atmospheric CO$_2 $ and climate, Nature, 302, 328–329, 1983. </reference>
		<reference numeration="51" content_type="text"> Mills, M. M., Ridame, C., Davey, M., LaRoche, J., and Geider, R. J.: Iron and phosphorus co-limit nitrogen fixation in the Eastern Tropical North Atlantic, Nature, 429, 292–294, 2004. </reference>
		<reference numeration="52" content_type="text"> Moisander, P. H., Paerl, H. W., Dyble, J., and Sivonen, K.: Phosphorus limitation and diel control of nitrogen-fixing cyanobacteria in the Baltic Sea, Mar. Ecol. Progr. Ser., 345, 41–50, 2007. </reference>
		<reference numeration="53" content_type="text"> Moisander, P. H., Shiue, L., Steward, G. F., Jenkins, B. D., Bebout, B. M., and Zehr, J. P.: Application of a nifH oligonucleotide microarray for profiling diversity of N&lt;sub&gt;2&lt;/sub&gt;-fixing microorganisms in marine microbial mats, Environ. Microbiol., 8, 1721–1735, 2006. </reference>
		<reference numeration="54" content_type="text"> Montoya, J. P., Holl, C. M., Zehr, J. P., Hansen, A., Villareal, T. A., and Capone, D. G.: High rates of N&lt;sub&gt;2&lt;/sub&gt; fixation by unicellular diazotrophs in the oligotrophic Pacific Ocean, Nature, 430, 1027–1031, 2004. </reference>
		<reference numeration="55" content_type="text"> Montoya, J. P., Voss, M., and Capone, D. G.: Spatial variation in N&lt;sub&gt;2&lt;/sub&gt;-fixation rate and diazotroph activity in the Tropical Atlantic, Biogeosciences, 4, 369–376, 2007. </reference>
		<reference numeration="56" content_type="text"> Morrison, J. M., Codispoti, L. A., Smith, S. L., Wishner, K., Flagg, C., Gardner, W. D., Gaurin, S., Naqvi, S. W. A., Manghnani, V., Prosperie, L., and Gundersen, J. S.: The oxygen minimum zone in the Arabian Sea during 1995, Deep-Sea Res. II, 46, 1903–1931, 1999. </reference>
		<reference numeration="57" content_type="text"> Mulholland, M. R.: The fate of nitrogen fixed by diazotrophs in the ocean, Biogeosciences, 4, 37–51, 2007. </reference>
		<reference numeration="58" content_type="text"> Naqvi, S. W. A., Jayakumar, D. A., Narvekar, P. V., Naik, H., Sarma, V. V. S. S., D&apos;Souza, W., Joseph, S., and George, M. D.: Increased marine production of N&lt;sub&gt;2&lt;/sub&gt;O due to intensifying anoxia on the Indian continental shelf, Nature, 408, 346–349, 2000. </reference>
		<reference numeration="59" content_type="text"> Naqvi, S. W. A., Naik, H., Pratihary, A., D&apos;Souza, W., Narvekar, P. V., Jayakumar, D. A., Devol, A. H., Yoshinari, T., and Saino, T.: Coastal versus open-ocean denitrification in the Arabian Sea, Biogeosciences, 3, 621–633, 2006. </reference>
		<reference numeration="60" content_type="text"> Nicholls, J. C., Davies, C. A., and Trimmer, M.: High-resolution profiles and nitrogen isotope tracing reveal a dominant source of nitrous oxide and multiple pathways of nitrogen gas formation in the central Arabian Sea, Limnol. Oceanogr., 52, 156–168, 2007. </reference>
		<reference numeration="61" content_type="text"> Ohlendieck, U., Gundersen, K., Meyerhfer, M., Fritsche, P., Nachtigall, K., and Bergmann, B.: The significance of nitrogen fixation to new production during early summer in the Baltic Sea, Biogeosciences, 4, 63–73, 2007. </reference>
		<reference numeration="62" content_type="text"> Ohkouchi, N., Kashiyama, Y., Kuroda, J., Ogawa, N. O., and Kitazato, H.: The importance of diazotrophic cyanobacteria as primary producers during Cretaceous Oceanic Anoxic Event 2, Biogeosciences, 3, 467–478, 2006. </reference>
		<reference numeration="63" content_type="text"> Otte, S., Kuenen, J. G., Nielsen, L. P., Paerl, H. W., Zopfi, J., Schulz, H. N., Teske, A., Strotmann, B., Gallardo, V. A., Jorgensen, B. B.: Nitrogen, carbon, and sulfur metabolism in natural \textitThioploca samples, Appl. Environ. Microbiol., 65, 3148–3157, 1999. </reference>
		<reference numeration="64" content_type="text"> Paerl, H. W., Valdes, L. M., Peierls, B. L., Adolf, J. E., and Harding, L. W., Jr.: Anthropogenic and climatic influences on the eutrophication of large estuarine ecosystems, Limnol. Oceanogr., 51, 448–462, 2006. </reference>
		<reference numeration="65" content_type="text"> Preisler, A., de Beer, D., Lichtschlag, A., Lavik, G., Boetius, A., and Jorgensen, B. B.: Biological and chemical sulfide oxidation in a \textitBeggiatoa inhabited marine sediment, ISME J., 1, 341–353, 2007. </reference>
		<reference numeration="66" content_type="text"> Rao, C. K., Naqvi, S. W. A., Kumar, M. D., Varaprasad, S. J. D., Jayakumar, D. A., George, M. D., and Singbal, S. Y. S.: Hydrochemistry of the Bay of Bengal: Possible reasons for a different watercolumn cycling of carbon and nitrogen from the Arabian Sea, Mar. Chem., 47, 279–290, 1994. </reference>
		<reference numeration="67" content_type="text"> Richards, F. A.: Comments on the effect of denitrification on the budget of combined nitrogen in the ocean, Extrait de la mer, Bull. Soc. Franco-Japanaise d&apos;Oceanographie, 9, 68–77, 1971. </reference>
		<reference numeration="68" content_type="text"> Risgaard-Petersen, N., Langezaal, A. M., Ingvardsen, S., Schmid, M. C., Jetten, M. S. M., Op den Camp, H. J. M., Derksen, J. W. M., Pina-Ochoa, E., Eriksson, S. P., Nielsen, L. P., Revsbech, N. P., Cedhagen, T., and van der Zwaan, G. J.: Evidence for complete denitrification in a benthic foraminifer, Nature, 443, 93–96, 2006. </reference>
		<reference numeration="69" content_type="text"> Rolff, C., Almesjo, L., and Elmgren, R.: Nitrogen fixation and abundance of the diazotrophic cyanobacterium \textitAphanizomenon sp in the Baltic Proper. Mar. Ecol. Progr. Ser., 332, 107-118, 2007. </reference>
		<reference numeration="70" content_type="text"> Sarmiento, J.: Interactive comment on &quot;An oceanic fixed nitrogen sink exceeding 400 TgNa&lt;sup&gt;&amp;minus;1&lt;/sup&gt; vs the concept of homeostasis in the fixed-nitrogen inventory&quot; by L. A. Codispoti, Biogeosciences Discuss., 3, S432–S440, 2006. </reference>
		<reference numeration="71" content_type="text"> Schulz, H. N., Brinkhoff, T., Ferdelman, T. G., Marine, M. H., Teske, A., and Jørgensen, B. B.: Dense populations of a giant sulfur bacterium in Namibian shelf sediments, Science, 284, 493–495, 1999. </reference>
		<reference numeration="72" content_type="text"> Seitzinger, S. P., Kroeze, C., Bouwman, A. E., Caraco, N., Dentener, F., Styles, R. V.: Global patterns of dissolved inorganic and particulate nitrogen inputs to coastal systems, Estuaries, 25, 640-655, 2002. </reference>
		<reference numeration="73" content_type="text"> Sigman, D. M., and Boyle, E. A.: Glacial/interglacial variations in atmospheric carbon dioxide, Nature, 407, 859–869, 2000. </reference>
		<reference numeration="74" content_type="text"> Sigman D. M., Granger, J., DiFiore, P. J., Lehmann, M. M., Ho, R., Cane, G., and van Geen, A.: Coupled nitrogen and oxygen isotope measurements of nitrate along the eastern North Pacific margin, Global Biogeochem. Cy., 19, GB4022, doi:10.1029/2005GB002458, 2005. </reference>
		<reference numeration="75" content_type="text"> Stramma, L., Johnson, G. C., Sprintall, J., and Mohrholz, V.: Expanding oxygen-minimum zones in the tropical oceans, Science, 320, 655-658, 2008. </reference>
		<reference numeration="76" content_type="text"> Strous, M., Fuerst, J. A., Kramer, E. H. M., Logemann, S., Muyzer, G., Van de Pas-Schoonen, K. T., Webb, R., Kuenen, J. G., and Jetten, M. S. M.: Missing lithothroph identified as new planctomycete, Nature, 400, 446–449. </reference>
		<reference numeration="77" content_type="text"> Thamdrup, B. and Dalsgaard, T.: Production of N&lt;sub&gt;2&lt;/sub&gt; through anaerobic ammonium oxidation coupled to nitrate reduction in marine sediments, Appl. Environ. Microbiol., 68, 1312–1318, 2002. </reference>
		<reference numeration="78" content_type="text"> Thamdrup, B., Dalsgaard, T., Jensen, M. M., Ulloa, O., Farias, L., and Escribano, R.: Anaerobic ammonium oxidation in the oxygen-deficient waters off northern Chile, Limnol. Oceanogr., 51, 2145–2156, 2006. </reference>
		<reference numeration="79" content_type="text"> Trimmer, M., Risgaard-Petersen, N., Nicholls, J. C., and Engstrom, P.: Direct measurement of anaerobic ammonium oxidation (anammox) and denitrification in intact sediment cores, Mar. Ecol. Prog. Ser., 326, 37–47, 2006. </reference>
		<reference numeration="80" content_type="text"> Voss, M., Deutsch, B., Elmgren, R., Humborg, C., Kuuppo, P., Pastuszak, M., Rolff, C., and Schulte, U.: Source identification of nitrate by means of isotopic tracers in the Baltic Sea catchments, Biogeosciences, 3, 663–676, 2006. </reference>
		<reference numeration="81" content_type="text"> Walter, S., Bange, H. W., Breitenbach, U., and Wallace, D. W. R.: Nitrous oxide in the North Atlantic Ocean, Biogeosciences, 3, 607–619, 2006a. </reference>
		<reference numeration="82" content_type="text"> Walter, S., Breitenbach, U., Bange, H. W., Nausch, G., and Wallace, D. W. R.: Distribution of N&lt;sub&gt;2&lt;/sub&gt;O in the Baltic Sea during transition from anoxic to oxic conditions, Biogeosciences, 3, 557–570, 2006b. </reference>
		<reference numeration="83" content_type="text"> Ward, B. B.: Molecular approaches to marine microbial ecology and the marine nitrogen cycle, Ann. Rev. Earth. Planet. Sci., 33, 301-333, 2005. </reference>
		<reference numeration="84" content_type="text"> Westley, M. B., Yamagishi, H., Popp, B. N., and Yoshida, N.: Nitrous oxide cycling in the Black Sea inferred from stable isotope and isotopomer distributions, Deep-Sea Res. II, 53, 1802–1816, 2006. </reference>
		<reference numeration="85" content_type="text"> Yamagishi, H., Westley, M. B., Popp, B. N., Toyoda, S., Yoshida, N., Watanabe, S., Koba, K., and Yamanaka, Y.: Role of nitrification and denitrification on the nitrous oxide cycle in the eastern tropical North Pacific and Gulf of California, J. Geophys. Res., 112, G02015, doi:10.1029/2006JG000227, 2007. </reference>
		<reference numeration="86" content_type="text"> Zehr, J. P., Mellon, M. T., and Zani, S.: New nitrogen-fixing microorganisms detected in oligotrophic oceans by amplification of nitrogenase (nifH) genes, Appl. Environ. Microbiol., 64, 3444–3450, 1998. </reference>
		<reference numeration="87" content_type="text"> Zehr, J. P., and Ward, B. B.: Nitrogen cycling in the ocean: New perspectives on processes and paradigms, Appl. Environ. Microbiol., 68, 1015–1024, 2002. </reference>
		<reference numeration="88" content_type="text"> Zehr, J. P., Waterbury, J. B., Turner, P. J., Montoya, J. P., Omoregie, E., Steward, G. F., Hansen, A., and Karl, D. M.: New nitrogen-fixing unicellular cyanobacteria discovered in the North Pacific Central Gyre, Nature, 412, 635–638, 2001. </reference>
		<reference numeration="89" content_type="text"> Zehr, J. P., Montoya, J. P., Jenkins, B. D., Hewson, I., Mondragon, E., Short, C. M., Church, M. J., Hansen, A., and Karl, D. M.: Experiments linking nitrogenase gene expression to nitrogen fixation in the North Pacific subtropical gyre, Limnol. Oceanogr., 52, 169–183, 2007. </reference>
	</references>
</article>

