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"Published Online September 22 2011 Science 28 October 2011: Vol. 334 no. 6055 pp. 505-509 DOI: 10.1126/science.1206583 Report Increasing N Abundance in the Northwestern Pacific Ocean Due to Atmospheric Nitrogen Deposition Tae-Wook Kim1, Kitack Lee1,*, Raymond G. Najjar2, Hee-Dong Jeong3, Hae Jin Jeong4 + Author Affiliations 1School of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang, 790−784, Korea. 2Department of Meteorology, The Pennsylvania State University, University Park, PA 16802, USA. 3East Sea Fisheries Research Institute, National Fisheries Research and Development Institute, Gangneung, 210-861, Korea. 4School of Earth and Environmental Sciences, Seoul National University, Seoul, 151−747, Korea. ↵*To whom correspondence should be addressed. E-mail: ktl@postech.ac.kr Abstract The relative abundance of nitrate (N) over phosphorus (P) has increased over the period since 1980 in the marginal seas bordering the northwestern Pacific Ocean, located downstream of the populated and industrialized Asian continent. The increase in N availability within the study area was mainly driven by increasing N concentrations and was most likely due to deposition of pollutant nitrogen from atmospheric sources. Atmospheric nitrogen deposition had a high temporal correlation with N availability in the study area (r = 0.74 to 0.88), except in selected areas wherein riverine nitrogen load may be of equal importance. The increase in N availability caused by atmospheric deposition and riverine input has switched extensive parts of the study area from being N-limited to P-limited. "

"Nitrogen (N2)-fixing microorganisms (diazotrophs) are an important source of biologically available fixed N in terrestrial and aquatic ecosystems and control the productivity of oligotrophic ocean ecosystems. We found that two major groups of unicellular N2-fixing cyanobacteria (UCYN) have distinct spatial distributions that differ from those of Trichodesmium, the N2-fixing cyanobacterium previously considered to be the most important contributor to open-ocean N2 fixation. The distributions and activity of the two UCYN groups were separated as a function of depth, temperature, and water column density structure along an 8000-kilometer transect in the South Pacific Ocean. UCYN group A can be found at high abundances at substantially higher latitudes and deeper in subsurface ocean waters than Trichodesmium. These findings have implications for the geographic extent and magnitude of basin-scale oceanic N2 fixation rates. "