Bedform characteristics and biofilm community development interact to modify hyporheic exchange.
Bedform characteristics and biofilm community development interact to modify hyporheic exchange.
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DOI：
10.1016/j.scitotenv.2020.141397
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发表时间：
2020-08
期刊：
影响因子：
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通讯作者：
Sarah Cook;O. Price;Andrew King;C. Finnegan;R. V. van Egmond;H. Schäfer;J. Pearson;S. Abolfathi;G. Bending
中科院分区：
文献类型：
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作者：
Sarah Cook;O. Price;Andrew King;C. Finnegan;R. V. van Egmond;H. Schäfer;J. Pearson;S. Abolfathi;G. Bending
河流生态系统的物理和生物属性以一种复杂的方式相互作用，可以影响系统的水动力行为。这可以改变河流在沉积物-水界面的混合特性。近年来，由于人们越来越认识到这种动态过渡带在连接和调节河流系统中的重要性，对潜流交换的研究有所增加。对驱动隐性交换的基于过程的相互作用的理解仍然有限，特别是物理和生物控制因素之间的反馈。实验研究了河床形态和沉积物粒度对生物膜群落发育的相互作用以及对潜水交换机制的影响。建造了专门的循环水槽系统，并研究了三种河床剖面：i)平坦，ii)波动λ = 1 m, ii)波动λ = 0.2 m，跨越两种不同大小的沉积物（0.5 mm和5 mm）。随着时间的推移，使用离散重复注射荧光染料到水槽中，探索了生物膜生长和床形相互作用对潜流交换的影响。在沉积物粒径较大（5 mm）和河床形态较多（波动λ = 0.2）的系统中，潜流交换率最高。沉积物大小是控制生物膜生长和低渗交换的主要控制因素。在河床普遍存在的系统中，由于平流泵的物理影响，沉积物大小和生物膜似乎不再是交换的控制因素。在这里，这些环境中的汇率随着时间的推移更加一致，尽管微生物的增长更快。因此，河床形态有潜力克服生物因素对潜水交换和沉积物大小对微生物渗透的速率限制作用。这对污染物和养分渗透有影响；河床增加了水文连通性，为深层微生物群落提供了支持，从而提高了河流系统的自净化能力。
The physical and biological attributes of riverine ecosystems interact in a complex manner which can affect the hydrodynamic behaviour of the system. This can alter the mixing characteristics of a river at the sediment-water interface. Research on hyporheic exchange has increased in recent years driven by a greater appreciation for the importance of this dynamic ecotone in connecting and regulating river systems. An understanding of process-based interactions driving hyporheic exchange is still limited, specifically the feedbacks between the physical and biological controlling factors. The interplay between bed morphology and sediment size on biofilm community development and the impact on hyporheic exchange mechanisms, was experimentally considered. Purpose built recirculating flume systems were constructed and three profiles of bedform investigated: i) flat, ii) undulating λ = 1 m, ii) undulating λ = 0.2 m, across two different sized sediments (0.5 mm and 5 mm). The influence of biofilm growth and bedform interaction on hyporheic exchange was explored, over time, using discrete repeat injections of fluorescent dye into the flumes. Hyporheic exchange rates were greatest in systems with larger sediment sizes (5 mm) and with more bedforms (undulating λ = 0.2). Sediment size was a dominant control in governing biofilm growth and hyporheic exchange in systems with limited bedform. In systems where bedform was prevalent, sediment size and biofilm appeared to no longer be a control on exchange due to the physical influence of advective pumping. Here, exchange rates within these environments were more consistent overtime, despite greater microbial growth. As such, bedform has the potential to overcome the rate limiting effects of biotic factors on hyporheic exchange and sediment size on microbial penetration. This has implications for pollutant and nutrient penetration; bedforms increase hydrological connectivity, generating the opportunity to support microbial communities at depth and as such, improve the self-purification ability of river systems.