Seaweed-assisted, benthic gravel transport by tidal currents

Frey, Shannon; Dashtgard, Shahin E.

doi:10.1016/j.sedgeo.2012.04.002

Cited by 12 publications

(9 citation statements)

References 22 publications

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“…Grain sizes range from 0.02 m to 0.25 m, with a mean size of 0.09 m. The grainonly model for incipient motion overpredicts the velocity required for transport of the measured grain sizes by a mean value of 81% and a maxi-mum of 92%. These findings agree well with the 92% reduction in velocity observed by a previous study in the Strait of Juan de Fuca (Frey and Dashtgard, 2012). None of the observations of kelp-assisted transport can be reconciled with the grain-only model for entrainment (Fig.…”

Section: Resultssupporting

confidence: 91%

“…The transport of large grains in anomalously low current conditions was noted by a number of these studies (Kudrass, 1974;Woodborne et al, 1989;Garden and Smith, 2011;Frey and Dashtgard, 2012), and deposits of large cobbles with kelp attached have been found in an estuary where current velocities are typically sufficient to only transport silt (Woodborne et al, 1989). These observations suggest that the attachment of large kelp fronds can substantially reduce the threshold for motion for large grains.…”

Section: Introductionmentioning

confidence: 75%

“…An experimental flume study found that this addition reduces the critical stress of all size fractions examined (Carling, 2014). Furthermore, a single in situ observation has shown that kelp-assisted transport can occur at current velocities far below the critical threshold for motion predicted by entrainment models that do not consider the impact of kelp (Frey and Dashtgard, 2012). However, a quantitative, mechanis-tic model for kelp-assisted entrainment has not been previously presented.…”

Section: Introductionmentioning

confidence: 99%

“…Kelp-assisted transport of large cobbles has been observed across the globe, including in southern Africa (Woodborne et al, 1989), northern Europe (Naylor et al, 2012), New Zealand (Garden and Smith, 2011), Antarctic regions (Emery and Tschudy, 1941), and both coasts of North America (Scheibling et al, 2009;Frey and Dashtgard, 2012), and has also been studied in experiments (Kudrass, 1974;Gilbert, 1984;Carling, 2014). The transport of large grains in anomalously low current conditions was noted by a number of these studies (Kudrass, 1974;Woodborne et al, 1989;Garden and Smith, 2011;Frey and Dashtgard, 2012), and deposits of large cobbles with kelp attached have been found in an estuary where current velocities are typically sufficient to only transport silt (Woodborne et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

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Kelp, cobbles, and currents: Biologic reduction of coarse grain entrainment stress

Masteller

Finnegan

Warrick

et al. 2015

Geology

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Models quantifying the onset of sediment motion do not typically account for the effect of biotic processes because they are difficult to isolate and quantify in relation to physical processes. Here we investigate an example of the interaction of kelp (Order Laminariales) and coarse sediment transport in the coastal zone, where it is possible to directly quantify and test its effect. Kelp is ubiquitous along rocky coastlines and the impact on ecosystems has been well studied. We develop a physical model to explore the reduction in critical shear stress of large cobbles colonized by Nereocystis luetkeana, or bull kelp. Observations of coarse sediment motion at a site in the Strait of Juan de Fuca (northwest United States-Canada boundary channel) confirm the model prediction and show that kelp reduces the critical stress required for transport of a given grain size by as much as 92%, enabling annual coarse sediment transport rates comparable to those of fluvial systems. We demonstrate that biology is fundamental to the physical processes that shape the coastal zone in this setting.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Kelp, cobbles, and currents: Biologic reduction of coarse grain entrainment stress

Masteller

Finnegan

Warrick

et al. 2015

Geology

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“…Such drag ging tends to be caused by shear stress ex erted on the slightly consol i dated sandy sur face layer due to the move ment of some mass. The mech a nism in volved is com monly a sed i ment-laden bot tom cur rent but can also be some thing dif fer ent, such as ice (e.g., Curran, 2007;Frey and Dashtgard, 2012;Salamon, 2015;Mazumder et al, 2016;Rana et al, 2016). How ever, such dragging re sults in the bend ing of foresets (if pres ent) in a reg u lar (not cha otic) way, so the CDL un der study can not be at trib uted to this pro cess.…”

Section: Comparison With Drag Structuresmentioning

confidence: 99%

Intrastratal flow in the Cretaceous Gyeokpori Formation (SW South Korea)

Byun

Loon

Kwon

et al. 2020

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Intrastratal flow is a pro cess that is still poorly un der stood, rarely de scribed and dif fi cult to in ter pret in an cient rocks. Sed iments in the Cre ta ceous lac us trine Gyeokpori For ma tion of south west ern South Ko rea con tain some cha ot i cally de formed sand stone lay ers with de formed mudstone clasts that are as cribed to this pro cess. The in ter pre ta tion is based on the fact that these lay ers can not be ex plained as a re sult of sub aque ous de bris flows or mass trans port, whereas the sed i men tary context, in clud ing the pres ence of other soft-sed i ment de for ma tion struc tures, in di cates that intrastratal flow must have been phys i cally pos si ble. The sed i men tary set ting was a lake in which mainly siliciclastic rocks were de pos ited, with some interbedded volcaniclastics. The nearby vol ca nic ac tiv ity caused seis mic shocks that af fected the un sta ble lake mar gins result ing in the dom i nance of grav ity-flow de pos its, but also in a high sed i men ta tion rate that fa cil i tated soft-sed i ment de for mation partly caused by intrastratal flow. This must have hap pened fairly fre quently dur ing a prob a bly lim ited time-span, as sev eral lay ers show ing traces of intrastratal flow are pres ent within a suc ces sion of only <1 m thick. The com bined data on the geo log i cal set ting and our find ings re gard ing the or i gin of the var i ous soft-sed i ment de for ma tion struc tures may help to rec og nize the traces left by intrastratal flow else where in the geo log i cal re cord. Key words: intrastratal flow, Gyeokpori For ma tion, soft-sed i ment de for ma tion struc tures, lac us trine en vi ron ment, Cre taceous.

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No evidence that seaweed cover enhances the deterioration of natural cement‐based mortar in intertidal environments

Baxter

Coombes

Viles

2022

Earth Surf Processes Landf

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The breakdown of rocks and engineering materials in marine environments is both enhanced and retarded by surface-colonizing marine organisms (seaweed, barnacles, etc.). However, the impact of marine growth on the deterioration of materials used to construct and repair maritime heritage assets, such as natural cement, is poorly understood.This study assesses whether seaweed cover (Fucus vesiculosus and Fucus serratus) influences the breakdown of mortar prepared using natural cement through an exposure trial at Portland Port, Dorset, UK. Using microclimate monitoring and three different indicators of weathering and material breakdown (surface hardness, surface roughness and ultrasonic pulse velocity), samples of mortar with and without a cover of seaweed were compared after 6 months of exposure to intertidal conditions. Our results show that temperature variations were significantly dampened under seaweed canopies compared to uncovered substrate both in summer and winter. As mechanical rock weathering processes are influenced by surface temperature regimes, we infer that these stabilizing effects may translate to a reduction in the efficacy of particular rock breakdown processes. Seaweed cover was not found to have significant effects on the surface hardness of the samples. Conversely, significant differences in surface roughness and pulse velocity were observed, indicating that the seaweed-covered samples experienced less surface and subsurface breakdown.Overall, we found no evidence that seaweed significantly enhances the deterioration of natural cement-based mortar during the first few months of exposure. Instead, we present the first empirical evidence of the bioprotective potential of seaweed covering materials commonly used in maritime built heritage restoration. Future work is now needed to examine the geomorphic roles of seaweed and other marine organisms on different types of materials used in maritime heritage conservation, and the extent to which their impacts on different deteriorative/protective processes vary in time and space, particularly under future climatic scenarios.

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Seaweed-assisted, benthic gravel transport by tidal currents

Cited by 12 publications

References 22 publications

Kelp, cobbles, and currents: Biologic reduction of coarse grain entrainment stress

Kelp, cobbles, and currents: Biologic reduction of coarse grain entrainment stress

Intrastratal flow in the Cretaceous Gyeokpori Formation (SW South Korea)

No evidence that seaweed cover enhances the deterioration of natural cement‐based mortar in intertidal environments

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