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- Title
The Resilience of Biofilm‐Bound Sandy Systems to Cyclic Changes in Shear Stress.
- Authors
Chen, Xindi; Zhang, Changkuan; Townend, Ian H.; Gong, Zheng; Feng, Qian; Yu, Xiping
- Abstract
Sand‐attached benthic biofilms drive many important biogeological processes and serve as cooperative "ecosystem engineers". In aquatic environments, biofilms undergo periodic detachment and re‐colonization due to the regular changes in hydrodynamic forcing. However, legacy impacts of past microbial actions on current biofilm formation and the biostabilization of the substratum sands are yet to be fully understood. In this study, a systematic set of flume experiments were conducted to investigate the effects of different depositional histories. Changes in the erosion threshold and rate of erosion were determined from the time sequences of suspended sediment concentrations. The contents of extracellular polymeric substances (EPS) and particle morphology of the biofilm‐bound sandy matrix were analyzed. Surprisingly, biostabilization is disturbance‐stimulated, rather than disturbance‐limited, as previously thought. Bio‐sandy beds cultivated under intensive disturbance presented an EPS accumulation in each cycle, and showed a more rapid increase in bed strength and stability than when rarely disturbed. All colonies from previous cycles exhibited traces of EPS as "footprints". These stimulated and possibly accelerated the process of recolonization, thereby enhancing the erosion resistance of the bed. In contrast, a stabilized bed was better suited to mature microbial communities. A modified "Windows of Opportunity" framework was therefore put forward. Although biostabilization was not established within short quiescent periods, the system created the "opportunity" to become established in subsequent "windows" by seeding the colonization process. The stabilization, destabilization and re‐stabilization of biofilm may imply a much more important role as ecosystem engineers and is relevant for a range of engineered bio‐systems. Plain Language Summary: "How can I stand on the ground every day and not feel its power? How can I live my life stepping on this stuff and not wonder at it?"—W. B. Logan. As the evidence for early life in the earth's sedimentary environment has shown, microorganisms are at least 3,770 million years old in sedimentary rocks, while each sand grain can harbor a highly diverse bacterial community. It is well known that biofilms, a heterogeneous matrix consisting of microbial communities and their secreted extracellular polymeric substances, can be critical in stabilizing sediments (defined as "biostabilization"), making the benthic stratum more habitable. However, legacy impacts of past microbial actions on current biofilm formation and the biostabilization of the substratum sands are yet to be fully understood. In this study, systematic flume experiments were conducted to investigate the effects of different depositional histories. Our findings highlight the resilience of bio‐sandy beds in response to changing shear. The fascinating interactions between biofilms and sands may help wetlands to survive sea‐level rise by inhibiting bed erosion and thereby enhancing their stability. This provides an important piece of information for the re‐assessment of wetland vulnerability in the face of global change. Key Points: Antecedent microbial conditions significantly influence the resilience of a biofilm‐bound sandy systemBiostabilization can be disturbance‐stimulated rather than disturbance‐limitedA framework is proposed for bio‐sandy systems developed under cyclic shear
- Subjects
SHEARING force; SEDIMENTARY rocks; BIOFILMS; SUSPENDED sediments; MICROBIAL communities; ABSOLUTE sea level change
- Publication
Water Resources Research, 2022, Vol 58, Issue 3, p1
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1029/2021WR031098