The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone
The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone
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DOI：
10.5194/bg-10-4767-2013
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发表时间：
2013-01-01
期刊：
影响因子：
4.9
通讯作者：
Sommer, S.
中科院分区：
文献类型：
--
作者：
Glock, N.;Schoenfeld, J.;Sommer, S.
有孔虫能够使用硝酸盐代替氧气作为呼吸的电子受体，这一发现挑战了我们对海洋中氮循环的理解。以前人们认为只有原核生物和一些真菌能够反硝化。有孔虫反硝化速率的估计非常稀少，而且仅限于海洋中的特定区域，而不是沿着某一区域的样带比较站。在这里，我们提出了在秘鲁氧气最小带（OMZ）及其以下的中等水深的六个站点的底栖有孔虫反硝化速率的估计。有孔虫反硝化速率是根据表层和地下沉积物中总活动物群的丰度和组合组成以及个别物种的特定反硝化速率计算的。与生物地球化学模型推断的底栖有孔虫总反硝化速率的比较表明，在80 ~ 250 m水深的陆架沉积物中，底栖有孔虫可能占了总反硝化作用。这些估算还表明，有孔虫在表层水体中心约320 m处仍然是重要的反硝化动物（占底栖动物反硝化作用的29-50%），但在表层水体下部边界和表层水体以下465 - 700 m处仅起次要作用（占底栖动物反硝化作用的2-6%）。此外，有孔虫反硝化作用已与底栖动物实验中测量的底栖动物硝酸盐总损失进行了比较。估计有孔虫反硝化率分别占80 ~ 700 m深度样带中硝酸盐总损失的2 ~ 46%。通量估计范围为0.01至1.3 mmol m(-2) d（-1）。此外，我们表明，与维持秘鲁OMZ沉积物中重要硝酸盐储层的近地表沉积物中的环境孔隙水相比，生活底栖有孔虫（3至3955 μ mol L-1）中储存的硝酸盐量可以高出三个数量级。秘鲁边缘是世界海洋中主要的硝酸盐汇区之一，有孔虫硝酸盐呼吸对底栖动物硝酸盐总损失的巨大贡献，支持了以前低估的底栖有孔虫在全球生物地球化学循环中的作用的重要性。
The discovery that foraminifera are able to use nitrate instead of oxygen as an electron acceptor for respiration has challenged our understanding of nitrogen cycling in the ocean. It was thought before that only prokaryotes and some fungi are able to denitrify. Rate estimates of foraminiferal denitrification have been very sparse and limited to specific regions in the oceans, not comparing stations along a transect of a certain region. Here, we present estimates of benthic foraminiferal denitrification rates from six stations at intermediate water depths in and below the Peruvian oxygen minimum zone (OMZ). Foraminiferal denitrification rates were calculated from abundance and assemblage composition of the total living fauna in both surface and subsurface sediments, as well as from individual species specific denitrification rates. A comparison with total benthic denitrification rates as inferred by biogeochemical models revealed that benthic foraminifera probably account for the total denitrification in shelf sediments between 80 and 250 m water depth. The estimations also imply that foraminifera are still important denitrifiers in the centre of the OMZ around 320 m (29-50% of the benthic denitrification), but play only a minor role at the lower OMZ boundary and below the OMZ between 465 and 700 m (2-6% of total benthic denitrification). Furthermore, foraminiferal denitrification has been compared to the total benthic nitrate loss measured during benthic chamber experiments. The estimated foraminiferal denitrification rates contribute 2 to 46% to the total nitrate loss across a depth transect from 80 to 700 m, respectively. Flux rate estimates range from 0.01 to 1.3 mmol m(-2) d(-1). Furthermore we show that the amount of nitrate stored in living benthic foraminifera (3 to 3955 mu mol L-1) can be higher by three orders of magnitude as compared to the ambient pore waters in near-surface sediments sustaining an important nitrate reservoir in Peruvian OMZ sediments. The substantial contribution of foraminiferal nitrate respiration to total benthic nitrate loss at the Peruvian margin, which is one of the main nitrate sink regions in the world ocean, underpins the importance of the previously underestimated role of benthic foraminifera in global biogeochemical cycles.