Overlooked bed shift? Modulation of the stream microbial food web and metabolism by patches of migrating sand ripples

被忽视的换床？

• 批准号: 400895888
• 负责人: Professor Dr. Michael Mutz
• 金额: --
• 依托单位: Lehrstuhl Gewässerschutz (aufgelöst)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/400895888?language=en
• 关键词: Overlooked; bed; shift; Modulation; stream

The overall objective of the project is to understand the significance of sediment disturbance in migrating sand ripples for the structure of the microbial food web and the metabolism in streams and rivers. The common concept of sediment disturbance in stream ecology focusses on 'catastrophic' singular big flood events that cause deep scour and far downstream relocation of sediments. However, low discharges can already relocate fine sediments. Streams with a large proportion of sandy sediments experience movement of sand in patches of migrating ripples (MRPs). MRPs occur over a wide range of flows and can cover the entire stream bed in the extreme. Given the increased input of sand in most cultivated catchments around the world, MRPs are a predominant feature in many, if not the majority of streams. Despite the phenomenon’s ubiquity, implications of migrating ripples on the microbial food web and metabolism have been largely neglected. Data from the few existing observational studies on the significance of shifting sands report contradicting findings. The aim of the proposed project is to clarify the significance of sediment disturbance by periodically shifting sands in MRPs for the microbial food web (community structure and functional feeding mode), carbon flow towards invertebrates (13C incorporation into PLFA of microorganisms and invertebrates) and stream bed metabolism (community respiration and gross primary production). Derived from previous studies we assume MRPs to change local (within ripple patch) and linked microbial food webs in stable bed sediment patches (SBPs) due to group or species-specific responses, and in turn affect the overall metabolism and trophic state of the streams. We propose i) sediment disturbance in MRPs to shift metabolism, microbial food web and carbon flow towards heterotrophy disregarding light intensity and nutrient concentrations, ii) that whole stream metabolism changes non-linearly in relation to MRP coverage due to increased overall vertical water flux to hyporheic stable sediments by MRPs and iii) that return of metabolism and microbial community structure after periodic sediment disturbance by ripple migration depends on duration in MRPs and light availability. The project approaches its objectives in a series of experiments in a laboratory microcosm device simulating the micro-environment in migrating ripples and in 16 outdoor experimental streams with variable proportion of MRPs and SBPs. The experiments will be completed and verified by field work measuring in situ metabolism and vertical water flux and observing the microbial food web and carbon flow in migrating ripples of streams and rivers. We want to achieve a mechanistic understanding for the whole stream metabolic effects of migrating ripple patches (MRPs). The project findings will significantly contribute to better valuate migrating sand in streams and rivers with implications for the management of ecosystem functions and services.

该项目的总体目标是了解迁移沙纹中沉积物扰动对溪流和河流中微生物食物网结构和新陈代谢的重要性。河流生态学中沉积物扰动的一般概念集中在“灾难性”的单一大洪水事件，导致深冲刷和远下游迁移的沉积物。然而，低排放量已经可以重新定位细沉积物。具有大比例桑迪沉积物的河流经历了在迁移波纹（MRP）斑块中的沙的运动。MRPs发生在很宽的流量范围内，在极端情况下可以覆盖整个河床。鉴于世界各地大多数耕作集水区的沙输入量增加，MRPs是许多（如果不是大多数）溪流的主要特征。尽管这种现象普遍存在，但迁移涟漪对微生物食物网和新陈代谢的影响在很大程度上被忽视了。现有的几项关于流沙重要性的观测研究的数据报告了相互矛盾的发现。拟议项目的目的是澄清沉积物扰动的意义，通过定期流沙的微生物食物网（社区结构和功能性喂养模式），碳流向无脊椎动物（13 C纳入PLFA的微生物和无脊椎动物）和河床代谢（社区呼吸和总初级生产力）。从以前的研究中，我们假设MRPs改变本地（内涟漪补丁）和链接的微生物食物网在稳定的床沉积物补丁（SBPs）由于组或物种特异性的反应，并反过来影响整体代谢和营养状态的流。我们提出i）在MRP中的沉积物扰动使代谢、微生物食物网和碳流转向异养，而不考虑光照强度和营养物浓度，ii）由于MRP增加了流向潜流稳定沉积物的总体垂直水通量，因此整个河流代谢与MRP覆盖率呈非线性关系，以及iii）在周期性的沉积物扰动后，通过涟漪迁移恢复新陈代谢和微生物群落结构取决于MRPs和光照的持续时间。该项目通过一系列实验来实现其目标，这些实验在实验室微观世界装置中模拟迁移波纹中的微环境，并在16个具有可变比例的MRP和SBP的室外实验流中进行。将通过实地工作完成和验证实验，测量原地新陈代谢和垂直水通量，观察溪流和河流迁移涟漪中的微生物食物网和碳流动。我们希望实现一个机制的理解，整个流的代谢效应迁移涟漪补丁（MRPs）。该项目的研究结果将大大有助于更好地评估溪流和河流中的流沙，并对生态系统功能和服务的管理产生影响。