Seasonal benthic nitrogen cycling in a temperate shelf sea: the Celtic Sea
Seasonal benthic nitrogen cycling in a temperate shelf sea: the Celtic Sea
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DOI：
10.1007/s10533-017-0311-3
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发表时间：
2017-03
期刊：
影响因子：
4
通讯作者：
V. Kitidis;K. Tait;Joana Nunes;I. Brown;E. Woodward;C. Harris;A. Sabadel;A. Sabadel;D. Sivyer;B. Silburn;S. Kröger
中科院分区：
文献类型：
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作者：
V. Kitidis;K. Tait;Joana Nunes;I. Brown;E. Woodward;C. Harris;A. Sabadel;A. Sabadel;D. Sivyer;B. Silburn;S. Kröger
2015 年，我们对凯尔特海大陆架的底栖 N 循环进行了季节性研究，并通过 2014 年的早期巡航进行了加强。2015 年的两次巡航集中在春季浮游植物盛开之前和之后，另一次巡航是在夏末进行的。所有航程均参观了从泥到沙连续体的五个地点，在那里我们确定了氨氧化、厌氧氨氧化和反硝化速率、厌氧氨氧化和反硝化基因的表达、氮养分通量和氮养分沉积物孔隙水剖面。最高的加工率出现在花后和夏末时期。凯尔特海主要是上覆水体无机氮的来源。硝酸盐的流出由铵氧化的程度控制。后者占粘性沉积物总耗氧量的 10-16%，占砂质沉积物总耗氧量的 35-56%。 0.001–2.288 mmol m−2days−1 范围内的铵氧化速率与沉积物孔隙度呈负相关，与有机质含量 (OM) 呈正相关，这共同解释了速率差异的 66%。氮去除主要是厌氧氨氧化 (0.003–0.636 mmol m−2days−1)，而不是反硝化作用 (0.000–0.034 mmol m−2days−1)。这一发现得到了相应基因表达数据的支持。肼氧化还原酶（厌氧氨氧化）的表达与厌氧氨氧化和总氮去除率显着相关。厌氧氨氧化与孔隙度和有机质呈正相关，而反硝化作用与有机质呈正相关。这些过程的氮需求主要是通过硝化（氨氧化）而不是从上覆水柱流入来满足的。我们估计，通过反硝化和厌氧氨氧化去除氮，从上覆水体中去除了沉积在海底的有机氮的 6-9%。凯尔特海系统因此失去了氮，必须每年补充氮以维持生产力。
We undertook a seasonal study of benthic N-cycling on the Celtic Sea continental shelf in 2015, augmented by an earlier cruise in 2014. Two cruises in 2015 were centred before and after the Spring phytoplankton bloom and a further cruise was carried out in late summer. Five sites covering the mud to sand continuum were visited on all cruises, where we determined ammonium-oxidation, anammox and denitrification rates, expression of anammox and denitrification genes, N-nutrient fluxes and sediment porewater profiles of N-nutrients. Highest process rates were found during the post-bloom and late summer periods. The Celtic Sea was overwhelmingly a source of inorganic-N to the overlying water column. The efflux of nitrate was controlled by the magnitude of ammonium-oxidation. The latter accounted for 10–16% of total Oxygen consumption in cohesive sediments and 35–56% in sandy sediments. Ammonium oxidation rates in the range of 0.001–2.288 mmol m−2days−1were inversely correlated with sediment porosity and positively correlated with organic matter content (OM) which together explained 66% of the variance in rates. N-removal was dominated by anammox (0.003–0.636 mmol m−2days−1), rather than denitrification (0.000–0.034 mmol m−2days−1). This finding was supported by the corresponding gene expression data. The expression of hydrazine oxidoreductase (anammox) was significantly correlated with anammox and total N-removal rates. Anammox was positively correlated with porosity and OM, whilst denitrification was correlated with OM. The N-requirement of these processes was largely met through nitrification (ammonium-oxidation) rather than influx from the overlying water column. We estimated that N-removal via denitrification and anammox removed 6–9% of the organic-N deposited at the sea-floor from the overlying water column. The Celtic Sea system was thereby losing N which must be replenished on an annual basis in order to sustain productivity.