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The effect of cyclic variation of shear stress on non-cohesive sediment stabilization by microbial biofilms: the role of ‘biofilm precursors’

The effect of cyclic variation of shear stress on non-cohesive sediment stabilization by microbial biofilms: the role of ‘biofilm precursors’
The effect of cyclic variation of shear stress on non-cohesive sediment stabilization by microbial biofilms: the role of ‘biofilm precursors’
Biofilm mediated intertidal sediments exhibit more complex erosional behaviour than abiotic systems. A major feature of intertidal systems is the exposure to repeated cycles of high and low shear created by tidal conditions and also less predictable episodic events, such as storms. There is very little information on how biofilm‐forming communities respond to these conditions. In this study, the effects of both single and repeated‐cycles of shear on the stability of newly developed bio‐sedimentary beds was examined. Cleaned sand, without any potential biostabilization, was used as the control. For the single‐cycle scenario, biofilms were incubated on a non‐cohesive sandy bed under prolonged low shear periods varying between 5 and 22 days, after which erosional stress was applied. No significant biostabilization was observed for the youngest bio‐sedimentary bed (after five days of low shear incubation). After 22 days, microbial communities were characterized by a firmly attached surface biofilm. To cause erosion, greater hydrodynamic stress (0.28 Pa) was required. The erosional behaviour of the underlying sand was also affected in that bedform ripples noted in the control system were no longer observed. Instead, a sudden ‘mass erosion’ took place (0.33 Pa). The one‐cycle scenario indicated that significant biostabilization of sand only occurred after a relative long calm period. Under repeated cycles of stress (five days of low stress followed by high stress event and re‐incubation, repeated for four cycles = 20 days), frequent cyclic disturbance did not degrade the system stability but enhanced biostabilization. The properties of the sub‐surface sediments were also affected where erosion rates were further inhibited. We hypothesize that organic material eroded from the bed acted as a ‘biofilm precursor’ supporting the development of new biofilm growth. A conceptual framework is presented to highlight the dynamics of bio‐sedimentary beds and the effects of growth history under repeated‐cycles.
0197-9337
Chen, Xindi
79f07552-4abc-407b-805e-0a16ee40a98c
Zhang, Changkuan
dfdb560e-6606-4ba2-86be-f7068ef48393
Paterson, David
2793dd09-9543-49bd-a3ac-6a34a1989234
Townend, Ian
f72e5186-cae8-41fd-8712-d5746f78328e
Jin, Chuang
2b035e2e-164f-46d0-ac58-23284c957fac
Zhou, Zeng
a167cd81-84c7-4e55-9e28-4529e26e7c01
Gong, Zheng
8fec227f-4dcc-431e-85c3-13a520574886
Feng, Qian
e5bc45a3-f8ed-479f-bd3e-5e10a8bd7bf3
Chen, Xindi
79f07552-4abc-407b-805e-0a16ee40a98c
Zhang, Changkuan
dfdb560e-6606-4ba2-86be-f7068ef48393
Paterson, David
2793dd09-9543-49bd-a3ac-6a34a1989234
Townend, Ian
f72e5186-cae8-41fd-8712-d5746f78328e
Jin, Chuang
2b035e2e-164f-46d0-ac58-23284c957fac
Zhou, Zeng
a167cd81-84c7-4e55-9e28-4529e26e7c01
Gong, Zheng
8fec227f-4dcc-431e-85c3-13a520574886
Feng, Qian
e5bc45a3-f8ed-479f-bd3e-5e10a8bd7bf3

Chen, Xindi, Zhang, Changkuan, Paterson, David, Townend, Ian, Jin, Chuang, Zhou, Zeng, Gong, Zheng and Feng, Qian (2019) The effect of cyclic variation of shear stress on non-cohesive sediment stabilization by microbial biofilms: the role of ‘biofilm precursors’. Earth Surface Processes and Landforms. (doi:10.1002/esp.4573).

Record type: Article

Abstract

Biofilm mediated intertidal sediments exhibit more complex erosional behaviour than abiotic systems. A major feature of intertidal systems is the exposure to repeated cycles of high and low shear created by tidal conditions and also less predictable episodic events, such as storms. There is very little information on how biofilm‐forming communities respond to these conditions. In this study, the effects of both single and repeated‐cycles of shear on the stability of newly developed bio‐sedimentary beds was examined. Cleaned sand, without any potential biostabilization, was used as the control. For the single‐cycle scenario, biofilms were incubated on a non‐cohesive sandy bed under prolonged low shear periods varying between 5 and 22 days, after which erosional stress was applied. No significant biostabilization was observed for the youngest bio‐sedimentary bed (after five days of low shear incubation). After 22 days, microbial communities were characterized by a firmly attached surface biofilm. To cause erosion, greater hydrodynamic stress (0.28 Pa) was required. The erosional behaviour of the underlying sand was also affected in that bedform ripples noted in the control system were no longer observed. Instead, a sudden ‘mass erosion’ took place (0.33 Pa). The one‐cycle scenario indicated that significant biostabilization of sand only occurred after a relative long calm period. Under repeated cycles of stress (five days of low stress followed by high stress event and re‐incubation, repeated for four cycles = 20 days), frequent cyclic disturbance did not degrade the system stability but enhanced biostabilization. The properties of the sub‐surface sediments were also affected where erosion rates were further inhibited. We hypothesize that organic material eroded from the bed acted as a ‘biofilm precursor’ supporting the development of new biofilm growth. A conceptual framework is presented to highlight the dynamics of bio‐sedimentary beds and the effects of growth history under repeated‐cycles.

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Accepted/In Press date: 20 December 2018
e-pub ahead of print date: 2 January 2019

Identifiers

Local EPrints ID: 429379
URI: https://eprints.soton.ac.uk/id/eprint/429379
ISSN: 0197-9337
PURE UUID: bbf012a4-2f3c-4e7a-a688-051a86bf6598
ORCID for Ian Townend: ORCID iD orcid.org/0000-0003-2101-3858

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Date deposited: 26 Mar 2019 17:30
Last modified: 27 Mar 2019 01:35

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Contributors

Author: Xindi Chen
Author: Changkuan Zhang
Author: David Paterson
Author: Ian Townend ORCID iD
Author: Chuang Jin
Author: Zeng Zhou
Author: Zheng Gong
Author: Qian Feng

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