Investigating biogenic heterogeneity in coastal sediments with two-dimensional measurements of iron(II) and sulfide
Investigating biogenic heterogeneity in coastal sediments with two-dimensional measurements of iron(II) and sulfide
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DOI：
10.1071/en08059
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发表时间：
2009-03
影响因子：
4.3
通讯作者：
David Robertson;D. Welsh;P. Teasdale
中科院分区：
文献类型：
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作者：
David Robertson;D. Welsh;P. Teasdale
环境背景。微生物呼吸作用通常发生在沿海沉积物的不同层中，产生高浓度的孔隙水铁或硫化物，尽管这种分层会因沉积物生物的活动而发生显著变化。本研究描述了使用一种新的技术，同时测量二维浓度的孔隙水铁和硫化物在毫米分辨率，允许斑块的模式，沉积物中的微生物呼吸被清楚地观察到。测量结果普遍支持的概念模型预测的影响，动物洞穴和海草根的孔隙水铁和硫化物的分布，虽然除了有机物提供了一些意想不到的意见，需要进一步调查。抽象的。沉积物地球化学中最有力的预测工具之一是电子受体分层模型，它描述了氧化化合物被呼吸微生物种群的演替所减少的顺序，以及这种分层如何受到底栖大型生物活动的影响。然而，技术允许方便的测定还原物质，如铁（II）和硫化物的非均匀分布，一直缺乏。结合扩散梯度薄膜扩散平衡薄膜技术被用来定量测量的二维铁（II）和硫化物的分布在高分辨率附近的各种沉积物功能，包括大型底栖动物洞穴，颗粒有机物和大型植物根。在所有的探针，特别是在海草根和颗粒有机物附近的两种分析物观察到实质性的异质性。测得的分布往往遵循的一般模式预测的第三电子受体分层模型。然而，在来自不同沉积物的几个样品中，特别是含有颗粒有机物和海草根的更复杂的沉积物中，硫化物和铁（II）的分布在毫米至厘米尺度上出现了意想不到的重叠。这种重叠的原因尚不清楚，需要进一步研究以阐明这种分布是如何发生的。
Environmental context. Microbial respiration generally occurs in distinct layers within coastal sediment, producing high porewater iron or sulfide concentrations, although this layering is dramatically modified by the activities of sediment-dwelling organisms. The present study describes use of a new technique to simultaneously measure two-dimensional concentrations of porewater iron and sulfide at millimetre resolution, allowing the patchiness of patterns of microbial respiration in sediment to be clearly observed. The measurements generally supported a conceptual model predicting the effects of animal burrows and seagrass roots on the porewater iron and sulfide distributions, although the addition of organic matter provided some unexpected observations that require further investigation. Abstract. One of the most powerful predictive tools in sediment biogeochemistry is the electron acceptor layering model, which describes the order in which oxidised compounds are reduced by successions of respiring microbial populations, and how this layering is influenced by benthic macro-organism activity. However, techniques allowing convenient determination of heterogeneous distributions of reduced substances, such as iron(II) and sulfide, have been lacking. A combined diffusive gradients in thin films–diffusive equilibrium in thin films technique was used to quantitatively measure the two-dimensional iron(II) and sulfide distributions at high resolution in the vicinity of various sediment features, including macrofauna burrows, particulate organic matter and macrophyte roots. Substantial heterogeneity was observed for both analytes in all probes, especially in the vicinity of seagrass roots and particulate organic matter. Measured distributions tended to follow the general patterns predicted by the tertiary electron acceptor layering model. However, there was unexpected overlap of sulfide and iron(II) distributions at the millimetre to centimetre scale in several samples from different sediments, notably the more complex sediments containing particulate organic matter and seagrass roots. The cause of such overlap is unclear and further study is necessary to elucidate how such distributions can occur.