ISI Document Delivery No.: 117IC Times Cited: 10 Cited Reference Count: 50 Cited References: Somes CJ, 2010, GLOBAL BIOGEOCHEM CY, V24, DOI 10.1029/2009GB003767 ANDERSON JJ, 1982, DEEP-SEA RES, V29, P1113, DOI 10.1016/0198-0149(82)90031-0 Behrenfeld MJ, 1997, LIMNOL OCEANOGR, V42, P1 Bertrand A, 2010, PLOS ONE, V5, DOI 10.1371/journal.pone.0010330 Bohlen L, 2011, GEOCHIM COSMOCHIM AC, V75, P6094, DOI 10.1016/j.gca.2011.08.010 Canfield DE, 2010, SCIENCE, V330, P1375, DOI 10.1126/science.1196889 CLINE JD, 1972, LIMNOL OCEANOGR, V17, P885 CODISPOTI LA, 1980, J MAR RES, V38, P453 CODISPOTI LA, 1985, MAR CHEM, V16, P277, DOI 10.1016/0304-4203(85)90051-9 Dalsgaard T, 2003, NATURE, V422, P606, DOI 10.1038/nature01526 Dalsgaard T, 2012, LIMNOL OCEANOGR, V57, P1331, DOI 10.4319/lo.2012.57.5.1331 Deutsch C, 2011, SCIENCE, V333, P336, DOI 10.1126/science.1202422 Deutsch C, 2001, GLOBAL BIOGEOCHEM CY, V15, P483, DOI 10.1029/2000GB001291 Diaz RJ, 2008, SCIENCE, V321, P926, DOI 10.1126/science.1156401 Fernandez C, 2009, PROG OCEANOGR, V83, P159, DOI 10.1016/j.pocean.2009.07.010 Fuenzalida R, 2009, DEEP-SEA RES PT II, V56, P1027, DOI 10.1016/j.dsr2.2008.11.001 Fussel J, 2012, ISME J, V6, P1200, DOI 10.1038/ismej.2011.178 GRASSHOFF K., 1999, METHODS SEAWATER ANA Gruber N., 2004, NATO ASI SER, P97 Gruber N, 1997, GLOBAL BIOGEOCHEM CY, V11, P235, DOI 10.1029/97GB00077 Hamersley MR, 2007, LIMNOL OCEANOGR, V52, P923 Holmes RM, 1999, CAN J FISH AQUAT SCI, V56, P1801, DOI 10.1139/cjfas-56-10-1801 Holtappels M, 2011, METHOD ENZYMOL, V486, P223, DOI [10.1016/B978-0-12-381294-0.00010-9, 10.1016/S0076-6879(11)86010-6] Jensen MM, 2011, ISME J, V5, P1660, DOI 10.1038/ismej.2011.44 Kalvelage T, 2011, PLOS ONE, V6, DOI 10.1371/journal.pone.0029299 KAMYKOWSKI D, 1990, DEEP-SEA RES, V37, P1861, DOI 10.1016/0198-0149(90)90082-7 Karstensen J, 2008, PROG OCEANOGR, V77, P331, DOI 10.1016/j.pocean.2007.05.009 Keeling R. F., 2009, ANNU REV MAR SCI, P463 Kuypers MMM, 2005, P NATL ACAD SCI USA, V102, P6478, DOI 10.1073/pnas.0502088102 Lam P, 2009, P NATL ACAD SCI USA, V106, P4752, DOI 10.1073/pnas.0812444106 Lam P, 2011, ANNU REV MAR SCI, V3, P317, DOI 10.1146/annurev-marine-120709-142814 Lam P, 2011, BIOGEOSCIENCES, V8, P1565, DOI 10.5194/bg-8-1565-2011 Lavik G, 2008, NATURE, V457, P581 Laws EA, 2000, GLOBAL BIOGEOCHEM CY, V14, P1231, DOI 10.1029/1999GB001229 LIPSCHULTZ F, 1990, DEEP-SEA RES, V37, P1513, DOI 10.1016/0198-0149(90)90060-9 Loescher C. R., 2012, BIOGEOSCI DISCUSS, V9, P2095, DOI DOI 10.5194/BGD-9-2095-2012 Moore JK, 2007, GLOBAL BIOGEOCHEM CY, V21, DOI 10.1029/2006GB002762 NAQVI SWA, 1987, J MAR RES, V45, P1049 Nelson S. S., 1979, DEEP SEA RES A, V26A, P1387 Pennington JT, 2006, PROG OCEANOGR, V69, P285, DOI 10.1016/j.pocean.2006.03.012 Revsbech NP, 2009, LIMNOL OCEANOGR-METH, V7, P371 Schmittner A, 2008, GLOBAL BIOGEOCHEM CY, V22, DOI 10.1029/2007GB002953 Stocker R, 2012, SCIENCE, V338, P628, DOI 10.1126/science.1208929 Stramma L, 2008, SCIENCE, V320, P655, DOI 10.1126/science.1153847 Thamdrup B, 2006, LIMNOL OCEANOGR, V51, P2145 Thamdrup B, 2012, DEEP-SEA RES PT I, V65, P36, DOI 10.1016/j.dsr.2012.03.001 Van Mooy BAS, 2002, GEOCHIM COSMOCHIM AC, V66, P457, DOI 10.1016/S0016-7037(01)00787-6 Ward BB, 2009, NATURE, V461, P78, DOI 10.1038/nature08276 WARD BB, 1989, DEEP-SEA RES, V36, P1031, DOI 10.1016/0198-0149(89)90076-9 WOOSTER WARREN S., 1965, J MAR RES, V23, P210 Kalvelage, Tim Lavik, Gaute Lam, Phyllis Contreras, Sergio Arteaga, Lionel Loescher, Carolin R. Oschlies, Andreas Paulmier, Aurelien Stramma, Lothar Kuypers, Marcel M. M. Lam, Phyllis/D-9574-2011; Lavik, Gaute/F-6578-2013; Oschlies, Andreas/F-9749-2012 Oschlies, Andreas/0000-0002-8295-4013 Deutsche Forschungsgemeinschaft through the Sonderforschungsbereich [754] We wish to thank the Peruvian government for access to their territorial waters. We sincerely thank the cruise leader M. Frank as well as the crews of the cruises M77-3 and 4 onboard R/V Meteor for their support at sea. We are grateful for the technical and analytical assistance of G. Klockgether, I. Boosmann, V. Leon, I. Grefe and A. Ellrott. We thank N. P. Revsbech, who generously provided the STOX sensors, and T. Ferdelmann for offering valuable comments to improve the article. This study was supported by the Deutsche Forschungsgemeinschaft through the Sonderforschungsbereich 754 'Climate-Biogeochemistry Interactions in the Tropical Ocean' and the Max Planck Society. 10 NATURE PUBLISHING GROUP NEW YORK NAT GEOSCI ; Oxygen minimum zones are expanding globally, and at present account for around 20-40% of oceanic nitrogen loss. Heterotrophic denitrification and anammox-anaerobic ammonium oxidation with nitrite-are responsible for most nitrogen loss in these low-oxygen waters. Anammox is particularly significant in the eastern tropical South Pacific, one of the largest oxygen minimum zones globally. However, the factors that regulate anammox-driven nitrogen loss have remained unclear. Here, we present a comprehensive nitrogen budget for the eastern tropical South Pacific oxygen minimum zone, using measurements of nutrient concentrations, experimentally determined rates of nitrogen transformation and a numerical model of export production. Anammox was the dominant mode of nitrogen loss at the time of sampling. Rates of anammox, and related nitrogen transformations, were greatest in the productive shelf waters, and tailed off with distance from the coast. Within the shelf region, anammox activity peaked in both upper and bottom waters. Overall, rates of nitrogen transformation, including anammox, were strongly correlated with the export of organic matter. We suggest that the sinking of organic matter, and thus the release of ammonium into the water column, together with benthic ammonium release, fuel nitrogen loss from oxygen minimum zones.