HR: 0800h
AN: B21A-0851    [Abstracts]
TI: Ammonia Oxidizing, Nitrite Reducing Bacteria and the Cycling of Nitrous Oxide in the Oxygen Minimum Zone (OMZ) of the Eastern South Pacific
AU: * Molina, V
EM: vemolina@udec.cl
AF: Universidad de Concepci\'{o}n, Departamento de Oceanograf\'{i}a, Facultad de Ciencias Naturales y Oceanogr\'{a}ficas, Casilla 160-C, Concepci\'{o}n, 4050030 Chile
AU: Castro-Gonz\'{a}lez, M
EM: maribcas@udec.cl
AF: Universidad de Concepci\'{o}n, Departamento de Oceanograf\'{i}a, Facultad de Ciencias Naturales y Oceanogr\'{a}ficas, Casilla 160-C, Concepci\'{o}n, 4050030 Chile
AU: Far\'{i}as, L
EM: lfarias@profc.udec.cl
AF: Universidad de Concepci\'{o}n, Departamento de Oceanograf\'{i}a, Facultad de Ciencias Naturales y Oceanogr\'{a}ficas, Casilla 160-C, Concepci\'{o}n, 4050030 Chile
AU: Far\'{i}as, L
EM: lfarias@profc.udec.cl
AF: Centro de Investigaci\'{o}n Oceanogr\'{a}fica Pac\'{i}fico Sur-Oriental (COPAS), Universidad de Concepci\'{o}n, Casilla 160-C, Concepci\'{o}n, 4050030 Chile
AU: Ulloa, O
EM: oulloa@profc.udec.cl
AF: Universidad de Concepci\'{o}n, Departamento de Oceanograf\'{i}a, Facultad de Ciencias Naturales y Oceanogr\'{a}ficas, Casilla 160-C, Concepci\'{o}n, 4050030 Chile
AU: Ulloa, O
EM: oulloa@profc.udec.cl
AF: Centro de Investigaci\'{o}n Oceanogr\'{a}fica Pac\'{i}fico Sur-Oriental (COPAS), Universidad de Concepci\'{o}n, Casilla 160-C, Concepci\'{o}n, 4050030 Chile
AU: Braker, G
EM: braker@mailer.uni-marburg.de
AF: Max Planck Institute f\"{u}r Terrestrial Microbiology, Karl-von-Frisch-Stra$\beta$e, Marburg, D-35043 Germany
AU: Witzel, K
EM: witzel@alpha1.mpil-ploen.mpg.de
AF: Max Planck Institute f\"{u}r Limnology, August-Thienemann-Stra$\beta$e 2, Pl\, D-24306 Germany
AB: The distribution of nitrous oxide, oxygen, nitrite and nitrate, and 16S rDNA and functional genes ({\it amoA},{\it nirS}) richness of ammonia oxidizing (AOB) and nitrite reducing bacteria (NRB) were studied in the water column of one of the shallowest ($<$50 m depth) and most severe (oxygen $<$4.5 $\mu$M) OMZ of the world's ocean. Results show two distinct environments in which nitrous oxide gets cycled. The first one is at the oxyclines, where high concentrations of up to 0.4 $\mu$M (3630%) of nitrous oxide are present. The second one is at the core of the OMZ, where low nitrous oxide concentration ($<$0.01 $\mu$M) are observed. A secondary nitrite maximum ($>$8 $\mu$M) is also present at the OMZ core. The relationship among apparent oxygen utilization (AOU), apparent nitrous oxide production, and nitrate distribution allowed the differentiation among nitrification, denitrification, and the coupling between both, at AOU values of $<$200, $>$230 and 200-230 $\mu$mol kg$^{-1}$, respectively. The richness of the AOB ribotypes (DGGE) and the NRB {it\nirS} TRFs increased towards the OMZ core, as well as the presence of the same kind of ribotypes and TRFs in the upper boundary and OMZ core. Our results suggest the existence of three nitrous oxide cycling layers in the upper 400 m (according to AOU analyses), where nitrification and denitrification contributes differently. In addition, the molecular evidence supports the coexistence of AOB and NRB in the upper boundary and core of the OMZ, in contrast with the conventional view of their vertical separation due to their different oxygen requirements.
DE: 4805 Biogeochemical cycles (1615)
DE: 4820 Gases
DE: 4834 Hypoxic environments
DE: 4803 Bacteria
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting