Silica Cycling and the Role of Diatoms in the Biological Pump of the Southern Ocean

这项工作是全球海洋通量联合研究南大洋实验中合作的44个项目之一。 南大洋实验是在南极极地锋区以南进行的一项为期三年的努力，旨在跟踪碳通过其有机和无机途径从空气-海洋界面通过整个水柱进入底部沉积物的流动。 JGOFS本身是对控制海洋中随时间变化的碳和相关生物元素通量的过程进行的十年期研究，目的是观察海洋生物地球化学循环与气候变化的关系。 实验将使用RVI B Nathaniel B。帕默和汤普森号 这一部分涉及从海洋表层去除有机碳的一般性问题，具体涉及硅藻，这是硅质浮游植物的一种形式，是南大洋生物泵的主要组成部分。 硅藻是已知的负责在极地锋区（PFZ）和沿着后退的冰边缘在罗斯海的主要生产。 硅藻硅通量和有机碳通量之间的强相关性表明，硅藻也是从南大洋表面沃茨输出的大部分有机物质的自养源。 硅藻在PFZ生物泵中的作用可能特别重要，因为南大洋几乎所有的硅通量都发生在PFZ之下，因此该区域和南部的沃茨构成了世界上最大的现代硅质沉积物积累区。 令人惊讶的是，巨大的蛋白石积累是由表面附近非常低的初级生产率支持的。 在水柱和上层沉积物中，碳和硅的区域循环分离到其他地方没有的程度，结果是在南大洋深海的大部分地区形成了富含蛋白石但有机物贫乏的沉积物。 该观测计划旨在揭示所产生的二氧化硅的命运，并帮助限制硅藻对该地区碳固定和出口的贡献。 将使用两种新开发的示踪剂方法。 第一个涉及使用新的放射性同位素的硅，32硅（半衰期134年），以测量二氧化硅的生产率。第二种是测量硅藻和海水中硅同位素的自然变化的新方法，该方法可能用作古二氧化硅生产水平的代理。 关于生物硅的大小，命运以及控制硅循环和硅藻生产力的因素所获得的见解将有助于评估硅藻在该地区元素的地球化学循环中的作用，并解释在南大洋硅藻硅高积累率的机制。

This work is one of forty-four projects that are collaborating in the Southern Ocean Experiment of the Joint Global Ocean Flux Study. The Southern Ocean Experiment is a three-year effort south of the Antarctic Polar Frontal Zone to track the flow of carbon through its organic and inorganic pathways from the air-ocean interface through the entire water column into the bottom sediment. JGOFS itself is a decadal study of the processes controlling the time-varying fluxes of carbon and associated biogenic elements in the ocean with the objective of observing changes in ocean biogeochemical cycles in relation to climatic change. The experiment will make use of the RVIB Nathaniel B. Palmer and the R/V Thompson. This component concerns the general topic of removal of organic carbon from the surface layers of the ocean, and deals specifically with diatoms, a form of siliceous phytoplankton, as a major component of the biological pump of the Southern Ocean. Diatoms are known to be responsible for the majority of primary production in the Polar Frontal Zone (PFZ) and along the retreating ice edge in the Ross Sea. Strong correlations between the fluxes of diatomaceous silica and organic carbon indicate that diatoms are also the autotrophic source of much of the organic matter exported from the surface waters of the Southern Ocean. The role of diatoms in the biological pump may be especially important in the PFZ, since nearly all of the silica flux in the Southern Ocean occurs beneath the PFZ with the result that this region and the waters to the south comprise the largest area of modern siliceous sediment accumulation in the world. Surprisingly, that immense opal accumulation is supported by very low rates of primary production near the surface. Within the water column and upper sediments the regional cycles of carbon and silica are decoupled to a degree that does not occur elsewhere, with the result that opal rich, but organic poor, sediments are forming throughout much of the abyssal Southern Ocean. The observational program is designed to reveal the fate of the silica produced and help constrain the contribution of diatoms to carbon fixation and export in the region. Two newly developed tracer methods will be used. The first involves the use of the newly available radioisotope of silicon, 32Si (half life 134 y), to measure silica production rates. The second is a new method for measuring natural variations in silicon isotopes within diatoms and seawater that may be useful as a proxy for level of paleo-silica production. The insights gained regarding the magnitude, fate of biogenic silica, and the factors controlling silica cycling and diatom productivity will help evaluate the role of diatoms in the biogeochemical cycling of elements in the region and explain the mechanisms producing high accumulation rates of diatom silica in the Southern Ocean.