The California Current transition zone off northern and central California: an extensive region exhibiting Fe-limitation and moderate chlorophyll

根据加州大学圣克鲁斯分校的一项研究，在加利福尼亚州海流(CC)过渡区近海观察到的高硝酸盐水平丝状水域来自沿海上升的海水，这些水域已经变得铁有限。这位科学家进一步提出，CC过渡区的铁限制会导致硝酸盐的减少和几周到几个月的时间尺度上的生物反应。这种缓慢的硝酸盐下降不同于位于相对宽阔的大陆架上的近岸地区，那里有充足的铁供应，允许浮游植物迅速繁殖，并在几天到一周的时间尺度上下降硝酸盐。为了确定铁限制在加州北部和中部加州海流(CC)过渡带浮游植物生物量控制中的作用，将于2010年在RV Point南部进行一次研究巡航，以确定以下内容：(1)加州北部和中部海岸各种上升区的营养物质、微量营养素和痕量金属的来源；(2)CC过渡区中大量营养素的升高是否是由于沿海上升流和随后的平流以及由于风应力或涡动作用而导致的近岸和陆架上升流的混合；(3)CC过渡区的Fe限制；(4)CC系统中与Fe有效性相关的营养消耗模式；(5)浮游植物群落对可浸出颗粒物Fe的再矿化/增溶和同化，以低丰度的Fe稳定同位素为示踪剂。至于更广泛的影响，本研究将加深我们对东部边界洋流地区浮游植物生物量和生态系统生产力的控制因素的认识。在教育影响方面，这项研究将为研究生和博士后提供科学培训。

High nitrate levels observed offshore in the California Current (CC) transition zone filament waters originate from coastal upwelled waters that have become iron-limited according to a research at the University of California-Santa Cruz. This scientist further proposes that iron-limitation in the CC transition zone results in nitrate drawdown and biological responses on time scales of a few weeks to months. This slow drawdown of nitrate differs from near-shore regions located over a relatively broad continental shelf with an adequate supply of iron allowing a rapid phytoplankton bloom and drawdown of nitrate on time scales of a few days to a week. To determine the role of Fe limitation in controlling phytoplankton biomass in the California Current (CC) transition zone off northern and central California, a research cruise, proposed to take place in 2010 on the RV Point Sur, would be carried out to determine the following: (1) the sources of nutrients, micronutrients, and trace metals from various upwelling regions along the northern and central coasts of California; (2) whether elevated macronutrients in the CC transition zone are due to coastal upwelling and subsequent advection and mixing offshore versus upwelling off the shelf due to curl of the wind stress or eddy dynamics; (3) Fe limitation in the CC transition zone; (4) nutrient consumption patterns in the CC system relative to Fe availability; and (5) remineralization/solubilization and assimilation of leachable particulate Fe by the phytoplankton community using low abundance stable isotopes of Fe as tracers.As regards broader impact, this study would further our knowledge on what controls phytoplankton biomass and ecosystem productivity in eastern boundary current regions, an economically important area. In regards to educational impacts, this research would provide scientific training for a graduate student and a postdoc.