| Autor: |
Widner B; Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, USA., Fuchsman CA; University of Washington, School of Oceanography, Seattle, USA.; Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, USA., Chang BX; Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, USA.; Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, USA., Rocap G; University of Washington, School of Oceanography, Seattle, USA., Mulholland MR; Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, USA. |
| Abstrakt: |
In marine oxygen deficient zones (ODZs), which contribute up to half of marine N loss, microbes use nitrogen (N) for assimilatory and dissimilatory processes. Here, we examine N utilization above and within the ODZ of the Eastern Tropical North Pacific Ocean, focusing on distribution, uptake and genes for the utilization of two simple organic N compounds, urea and cyanate. Ammonium, urea and cyanate concentrations generally peaked in the oxycline while uptake rates were highest in the surface. Within the ODZ, concentrations were lower, but urea N and C and cyanate C were taken up. All identified autotrophs had an N assimilation pathway that did not require external ammonium: ODZ Prochlorococcus possessed genes to assimilate nitrate, nitrite and urea; nitrite oxidizers (Nitrospina) possessed genes to assimilate nitrite, urea and cyanate; anammox bacteria (Scalindua) possessed genes to utilize cyanate; and ammonia-oxidizing Thaumarchaeota possessed genes to utilize urea. Urease genes were present in 20% of microbes, including SAR11, suggesting the urea utilization capacity was widespread. In the ODZ core, cyanate genes were largely (∼95%) associated with Scalindua, suggesting that, within this ODZ, cyanate N is primarily used for N loss via anammox (cyanammox), and that anammox does not require ammonium for N loss. |
