Role of iron as a regulator of nitrogen cycle in the subsurface ocean

作为亚硝酸盐最大值（subsurface nitrite maximum， SNM）形成的机制，我们通过测量叶绿素最大表层附近铁和营养物质的详细分布，验证了一个假设，即铁限制刺激浮游植物细胞向周围水体释放亚硝酸盐。虽然东海浮游植物的组合不受铁的限制，但在西北太平洋附近观测到的极低浓度的溶解铁似乎支持了北太平洋西部的假设。然而，在北太平洋的亚北极水域，由于高环境铵浓度，古细菌氨氧化也可能有助于SNM的形成

As a mechanism for the formation of the subsurface nitrite maximum (SNM), a hypothesis that iron limitation stimulates nitrite release from phytoplankton cells to the surrounding water, was examined in the oceanic waters, by measuring detailed distributions of iron and nutrients near the subsurface chlorophyll maximum layer. Although phytoplankton assemblage in the East China Sea was not under iron-limitation, extremely low concentration of dissolved iron observed near the SNMseems to support the hypothesis in the western North Pacific. In the subarctic waters of the North Pacific, however, archaeal ammonia oxidation may also contribute to the formation of the SNM, because of the high ambient ammonium concentrations