12.13 Ecogeomorphology of Tidal Flats

Fagherazzi, Sergio; FitzGerald, Duncan M.; Fulweiler, Robinson W.; Hughes, Zoë; Wiberg, P. L.; McGlathery, K. J.; Morris, James T.; Tolhurst, T.J.; Deegan, Linda A.; Johnson, David Samuel

doi:10.1016/b978-0-12-374739-6.00403-6

Cited by 10 publications

(17 citation statements)

References 85 publications

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“…These crinkle‐comprising layers, whose dark colour might reflect lower density associated with porous, felt‐like Vaucheria mats, are most abundant at depths that likely coincide with the years 2011–2013, in which the strongest algal cover is observed (Figures and ). Layering is much less evident in bare runnel sediments, despite similar year‐averaged accretion rates in runnels and on ridges (or creeks and levees), which is in agreement with earlier studies showing that ridge/levee sediments are more gradually deposited and more (a)biotically stabilized, whereas runnel/creek sediments have higher turnover rates (Blanchard et al ., ; Gouleau et al ., ; O'Brien et al ., ; Lanuru et al ., ; Williams et al ., ; Carling et al ., ; Fagherazzi et al ., ). Indeed, algal‐covered creek levees were found to have significantly higher penetration resistance than bare creek levees and runnels (Figure ).…”

Section: Discussionmentioning

confidence: 97%

“…In any case, the observation of flattened bedforms (topographic relief halved in September 2017, as compared to August 2015 and December 2016), seemingly following a temporal shift of Vaucheria from ridges to runnels between May and July 2017 (Figure SI9a), seems to support the expectation that biofilms can significantly contribute to bedform formation and maintenance (e.g. de Boer, ; Blanchard et al ., ; Lanuru et al ., ; Friend et al ., ; Weerman et al ., ; Fagherazzi et al ., ; Mariotti et al ., ). This disruption of the spatial biostabilization pattern might be short‐term, due to disintegration of Vaucheria filaments at high temperatures (Gallagher and Humm, ), or announcing a critical point in bedform self‐organization which is reached when the accretionary mudflat is no longer inundated with sufficient frequency (as observed for stromatolites; Logan, ).…”

Section: Discussionmentioning

confidence: 98%

“…Although this feedback can be purely geophysical, ridge colonization by biostabilizers might amplify the stability contrast (ridge vs runnel) and hence the feedback (e.g. Blanchard et al ., ; Lanuru et al ., ; Williams et al ., ; Weerman et al ., ; Fagherazzi et al ., ).…”

Section: Introductionmentioning

confidence: 97%

“…Multicellular algae like Vaucheria were rare in the Precambrian, but not absent (Butterfield, ). For the purpose of this study, the definition of biofilms will therefore be slightly broadened (following Fagherazzi et al ., ) to include functionally similar mats composed of multicellular macroalgae. Do such mats create laminated and patterned bedforms, contributing to long‐term estuarine morphodynamics just like cyanobacteria and other microbialite‐building organisms did from the Precambrian onwards (Noffke, , ; Noffke and Krumbein, ; Riding, )?…”

Section: Introductionmentioning

confidence: 99%

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Estuarine biofilm patterns: Modern analogues for Precambrian self‐organization

Vijsel

Belzen

Bouma

et al. 2020

Earth Surf Processes Landf

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This field and laboratory study examines whether regularly patterned biofilms on present‐day intertidal flats are equivalent to microbially induced bedforms found in geological records dating back to the onset of life on Earth. Algal mats of filamentous Vaucheria species, functionally similar to microbial biofilms, cover the topographic highs of regularly spaced ridge–runnel bedforms. As regular patterning is typically associated with self‐organization processes, indicators of self‐organization are tested and found to support this hypothesis. The measurements suggest that biofilm‐induced sediment trapping and biostabilization enhance bedform relief, strength and multi‐year persistence. This demonstrates the importance of primitive organisms for sedimentary landscape development. Algal‐covered ridges consist of wavy‐crinkly laminated sedimentary deposits that resemble the layered structure of fossil stromatolites and microbially induced sedimentary structures. In addition to layering, both the morphological pattern and the suggested formation mechanism of the recent bedforms are strikingly similar to microbialite strata found in rock records from the Precambrian onwards. This implies that self‐organization was an important morphological process in times when biofilms were the predominant sessile ecosystem. These findings furthermore emphasize that self‐organization dynamics, such as critical transitions invoking ecosystem emergence or collapse, might have been captured in fossil microbialites, influencing their laminae. This notion may be important for paleoenvironmental reconstructions based on such strata. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Estuarine biofilm patterns: Modern analogues for Precambrian self‐organization

Vijsel

Belzen

Bouma

et al. 2020

Earth Surf Processes Landf

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“…In the typical erosion‐transportation‐deposition‐consolidation cycle, erosion is mediated as a result of the redistribution of stability in the sediment bed via the EPS effects. One of the most important effects of biofilms is their ability to stabilize sediments, which then become more resistant to erosion (Fagherazzi et al, ). In this respect, a phenomenon called “biostabilization” occurs, defined as “a decrease in sediment erodibility caused by biological actions” (Paterson & Daborn, ).…”

Section: Introductionmentioning

confidence: 99%

Stabilizing Effects of Bacterial Biofilms: EPS Penetration and Redistribution of Bed Stability Down the Sediment Profile

et al. 2017

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Biofilms, consisting of microorganisms and their secreted extracellular polymeric substances (EPSs), serve as “ecosystem engineers” stabilizing sedimentary environments. Natural sediment bed provides an excellent substratum for biofilm growth. The porous structure and rich nutrients allow the EPS matrix to spread deeper into the bed. A series of laboratory‐controlled experiments were conducted to investigate sediment colonization of Bacillus subtilis and the penetration of EPS into the sediment bed with incubation time. In addition to EPS accumulation on the bed surface, EPS also penetrated downward. However, EPS distribution developed strong vertical heterogeneity with a much higher content in the surface layer than in the bottom layer. Scanning electron microscope images of vertical layers also displayed different micromorphological properties of sediment‐EPS matrix. In addition, colloidal and bound EPSs exhibited distinctive distribution patterns. After the full incubation, the biosedimentary beds were eroded to test the variation of bed stability induced by biological effects. This research provides an important reference for the prediction of sediment transport and hence deepens the understanding of the biologically mediated sediment system and broadens the scope of the burgeoning research field of “biomorphodynamics.”

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Hindered erosion: The biological mediation of noncohesive sediment behavior

Chen

Zhang

Paterson

et al. 2017

Water Resources Research

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Extracellular polymeric substances (EPS) are ubiquitous on tidal flats but their impact on sediment erosion has not been fully understood. Laboratory-controlled sediment beds were incubated with Bacillus subtilis for 5, 10, 16, and 22 days before the erosion experiments, to study the temporal and spatial variations in sediment stability caused by the bacterial secreted EPS. We found the biosedimentary systems showed different erosional behavior related to biofilm maturity and EPS distribution. In the first stage (5 days), the biosedimentary bed was more easily eroded than the clean sediment. With increasing growth period, bound EPS became more widely distributed over the vertical profile resulting in bed stabilization. After 22 days, the bound EPS was highly concentrated within a surface biofilm, but a relatively high content also extended to a depth of 5 mm and then decayed sharply with depth. The biofilm increased the critical shear stress of the bed and furthermore, it enabled the bed to withstand threshold conditions for an increased period of time as the biofilm degraded before eroding. After the loss of biofilm protection, the high EPS content in the sublayers continued to stabilize the sediment (hindered erosion) by binding individual grains, as visualized by electron microscopy. Consequently, the bed strength did not immediately revert to the abiotic condition but progressively adjusted, reflecting the depth profile of the EPS. Our experiments highlight the need to treat the EPS-sediment conditioning as a bed-age associated and depth-dependent variable that should be included in the next generation of sediment transport models. Plain Language Summary Sedimentology and geomorphology have traditionally been seen as fields in which physical and chemical processes dominate. However, microbial communities should never be bystanders, because they suffuse all sedimentary environments on earth. Under hydrodynamic forces, they take part in an impressive range of sediment processes and thus exercising a formative influence on coastal evolutions. Bio-sediments exhibit more complex characteristics than abiotic systems, and lead to different modelling methods compared to those in traditional settings. For instance, the thresholds for sediment initiation and subsequent erosion rates are no longer solely related to particle properties (e.g., particle size, the most widely used), but mediated by glue-like extracellular polymeric substances (EPS) secreted by microbes. From this point of view, it is easy to understand why sediments in field observations behave differently from predictions, usually appearing considerably strengthened. Our results indicate that the EPS mediation in sediment stability may vary with the rhythms of microbial growth, and re-profile the sediment stability during different stages of cementing processes. A conceptual framework for sediment erosion is hence put forward to transform traditional sediment system to EPS-sediment system.

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12.13 Ecogeomorphology of Tidal Flats

Cited by 10 publications

References 85 publications

Estuarine biofilm patterns: Modern analogues for Precambrian self‐organization

Estuarine biofilm patterns: Modern analogues for Precambrian self‐organization

Stabilizing Effects of Bacterial Biofilms: EPS Penetration and Redistribution of Bed Stability Down the Sediment Profile

Hindered erosion: The biological mediation of noncohesive sediment behavior

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