Villareal Tracy A, Pilskaln Cynthia, Brzezinski Mark, Lipschultz Fredric, Dennett Mark, Gardner George B
Marine Science Institute, The University of Texas at Austin, 750 Channel View Drive, Port Aransas, Texas 78373, USA.
School of Marine Sciences, 5741 Libby Hall, University of Maine, Orono, Maine 04469, USA.
Nature. 1999 Feb 4;397(6718):423-425. doi: 10.1038/17103.
The oligotrophic gyres of the open sea are home to a flora that includes the largest known phytoplankton. These rare species migrate as solitary cells or aggregations (mats) between deep nutrient pools (below 80-100 m) and the surface. This migration contributes to new production because of the concomitant upward transport of nitrate. But just how significant this contribution is remains uncertain because of the difficulty of making quantitative measurements of these rare cells. Here we report remote video observations of a previously undersampled class of diatom (Rhizosolenia) mats throughout the upper 150 m of the central North Pacific Ocean. These mats are virtually invisible to divers, and their presence increases the calculated phytoplankton-mediated nitrate transport into the surface ocean by up to a factor of eight. Cruise averages indicate that Rhizosolenia mats transport 18-97 µmol N m d; however, this value reached 171 μmol N m d at individual stations, a value equivalent to 59% of the export production. Although considerable temporal and spatial variability occurs, this means of upward nutrient transport appears to be an important source of new nitrogen to the surface ocean, and may contribute to other regional elemental cycles as well.
公海中的贫营养环流是包括已知最大浮游植物在内的一种植物群落的栖息地。这些稀有物种以单个细胞或聚集体（席状）的形式在深层营养库（80 - 100米以下）和海面之间迁移。由于硝酸盐随之向上运输，这种迁移促进了新的生产力。但由于难以对这些稀有细胞进行定量测量，这种贡献究竟有多大仍不确定。在这里，我们报告了对北太平洋中部上层150米范围内一类此前采样不足的硅藻（根管藻）席状聚集体的远程视频观测结果。这些席状聚集体对潜水员来说几乎不可见，它们的存在使计算得出的浮游植物介导的硝酸盐向表层海洋的运输量增加了多达八倍。航次平均值表明，根管藻席状聚集体运输18 - 97微摩尔氮/米²/天；然而，在个别站点该值达到171微摩尔氮/米²/天，这一数值相当于输出生产力的59%。尽管存在相当大的时间和空间变异性，但这种向上的营养物质运输方式似乎是表层海洋新氮的一个重要来源，并且可能也对其他区域的元素循环有贡献。
