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首页> 外文期刊>Ecosystems >Net Sediment N2 Fluxes in a Coastal Marine System—Experimental Manipulations and a Conceptual Model
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Net Sediment N2 Fluxes in a Coastal Marine System—Experimental Manipulations and a Conceptual Model

机译：沿海海洋系统中的净沉积物N2 通量—实验操作和概念模型

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Environmental factors, including the supply of organic matter and inorganic nutrient concentrations, are thought to influence rates of two opposing processes in the nitrogen (N) cycle, denitrification and N fixation. Using sediment cores from a temperate estuary we examined the effects of nitrate, phosphate, and ammonium enrichment of the overlying water on the net N2 flux across the sediment–water interface. In addition, we used sediment cores and large marine mesocosms to determine the effect of organic matter amendment. The addition of nitrate (50 μM), ammonium (50 μM), and phosphate (10 μM) to the overlying water had no effect on the net N2 flux. However, high ammonium fluxes (145 μmol m?2 h?1) were observed in the nitrate-amended cores, which is suggestive of dissimilatory nitrate reduction to ammonium. Organic matter enrichment first increased rates of N fixation, but ultimately switched the sediments from being a net source (N fixation dominated) to a net sink (denitrification dominated) of N. We observed a threshold where N fixation took place when organic matter deposition fell below about 0.3 g C m?2 day?1. On the basis of these results and the findings of others, we developed a conceptual model that links net sediment N2 flux with the organic matter production of a system.
机译：环境因素，包括有机物的供应和无机营养物的浓度，被认为会影响氮（N）循环中两个相反过程（反硝化和固氮）的速率。利用温带河口的沉积物核，我们研究了覆盖水的硝酸盐，磷酸盐和铵的富集对沉积物-水界面上净N2 通量的影响。另外，我们使用了沉积物核心和大型海洋中观来确定有机物修正的效果。在上层水中添加硝酸盐（50μM），铵（50μM）和磷酸盐（10μM）对净N2 通量没有影响。然而，在硝酸盐修饰的岩心中观察到较高的铵通量（145μmolm？2 h？1 ），这表明硝酸盐可异化地还原为铵盐。有机质富集首先增加了固氮率，但最终使沉积物从氮的净源（固氮为主）变为净水槽（反硝化为主）。我们观察到有机质沉积下降时固氮发生的阈值。低于约0.3 g C m？2 天？1 。根据这些结果和其他发现，我们建立了一个概念模型，将净沉积物N2 通量与系统的有机物产生联系起来。

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