Anoxic microniches in marine sediments induced by aggregate settlement: biogeochemical dynamics and implications
Anoxic microniches in marine sediments induced by aggregate settlement: biogeochemical dynamics and implications
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DOI：
10.1007/s10533-014-9967-0
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发表时间：
2014-06-01
期刊：
影响因子：
4
通讯作者：
Davison, William
中科院分区：
文献类型：
--
作者：
Lehto, Niklas;Glud, Ronnie N.;Davison, William
将球形（直径约 2 毫米）硅藻（Skeletonema sp.）聚集体（代表“海洋雪”的类似物）放置在实验沉积物系统的沉积物-水界面处。光极测量表明，经过最初的滞后期后，聚集体内的氧气浓度下降，然后逐渐补充，导致暂时的缺氧微生态位。使用多物种、三维、反应性传输模型来模拟氧动力学和相关的生物地球化学后果。假设矿化速率常数呈指数增加且活性有机物质逐渐耗尽，则复制了氧的时间和空间变化。有机质矿化的时间依赖性反应速率常数 (k (OMM)) 的峰值比之前在水柱实验中测量的类似值大七到六十倍。经过验证的模型用于研究有机物块的大小和反应性如何影响典型深海环境的沉积物-水界面处缺氧微生态位的形成。除了 k (OMM) 之外，聚集体中反应性有机物的浓度、其尺寸和孔隙率对于确定缺氧微生态位形成的可能性也至关重要。对于描述 k (OMM) 和活性有机物浓度的最佳拟合参数，引起缺氧的最小直径为 1.8 mm，而对典型深海沉积物中发生的反硝化作用做出显着贡献的最小直径为 2.8 mm。这项工作表明，海洋聚集体沉降产生的缺氧微生态位可能在深海沉积物的反硝化活动中发挥着被忽视的作用。
Spherical (similar to 2 mm diameter) diatom (Skeletonema sp.) aggregates, representing analogues of "marine snow", were placed at the sediment-water interface of an experimental sediment system. Optode measurements showed that, after an initial lag period, oxygen concentrations within the aggregates decreased and then were gradually replenished, resulting in a temporary anoxic microniche. A multi-species, 3-dimensional, reactive transport model was used to simulate the oxygen dynamics and the associated biogeochemical consequences. Temporal and spatial changes in oxygen were replicated assuming an exponential increase in the mineralisation rate constant and a gradual exhaustion of reactive organic material. The peak value of the time-dependent reaction rate constant of organic matter mineralisation (k (OMM)) was seven to sixty times greater than analogous values measured previously in water column experiments. The validated model was used to investigate how the size and reactivity of parcels of organic matter influence the formation of anoxic microniches at the sediment-water interface of typical deep-sea environments. As well as k (OMM), the concentration of reactive organic matter in the aggregate, its size and porosity were also critical in determining the likelihood of anoxic microniche formation. For the optimum fitted parameters describing k (OMM) and the concentration of reactive organic matter, the minimum diameter of the parcel to induce anoxia was 1.8 mm, whereas it was 2.8 mm to make a significant contribution to the denitrification occurring in a typical deep-sea sediment. This work suggests that anoxic microniches resulting from the settlement of marine aggregates may play an overlooked role for denitrification activities in deep-sea sediments.