Sediment sampling evaluated with a new weighting function and index of reliability

Floderus, Sören

doi:10.1007/978-94-009-2376-8_44

Cited by 3 publications

(4 citation statements)

References 6 publications

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“…Such work has been extended in two main directions. First, various workers have attempted to improve the statistical basis for sampling by considering the number of cores necessary to provide an acceptable level of precision in the estimation of whole lake sedimentation rates (e.g., Håkanson ; Baudo et al ; Floderus ). Second, efforts have been made to improve the dynamic basis of the sediment focusing model.…”

Section: Discussionmentioning

confidence: 99%

Three‐dimensional hydrodynamic and sediment transport modeling to test the sediment focusing hypothesis in upland lakes

Morales-Marín

French

Burningham

et al. 2017

Limnology & Oceanography

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Palaeolimnological studies rely on assumptions regarding the distribution and completeness of lake deposits that are not always fully supported by observations. In particular, the assumption that "focusing" of suspended sediments leads to preferential deposition in the deepest part of a lake is not always justified, especially in upland lakes subject to energetic wind forcing. Few studies have investigated the hydrodynamic controls on lake sediment focusing, especially the importance of wind-driven currents in deep water. We combine a three-dimensional numerical hydrodynamic and suspended sediment model (FVCOM) with a semi-empirical wind wave model to investigate the potential mobility of bottom sediments in a small oligotrophic upland lake (Llyn Conwy, north Wales, UK). Exploratory simulations of wave-and current-generated bottom stress and suspended sediment dynamics confirm the expected importance of wave-generated bottom stresses in shallower waters (< 3 m depth) around the shore. Field survey shows that lake sediments are largely absent from this zone. This is consistent with peripheral wave action as a sediment focusing mechanism. In deeper water, wind-driven currents become the dominant contributor to bottom stress. Strong wind forcing events drive an energetic circulation with peak bottom stresses that intermittently exceed any realistic erosion threshold over a large proportion of the lake at depths far below those at which waves can be effective. The spatial distribution of lake sediments, and the completeness of the sediment record, is thus determined by a complex interaction between wind-driven circulation and bathymetry, rather than by bathymetry alone. Although our sediment dynamics simulations are purely exploratory, the results are consisted with survey results that show a patchy distribution of deep-water accumulation. Some implications of these results for the selection of sediment coring locations and the interpretation of sediment records are considered.

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Section: Discussionmentioning

confidence: 99%

Three‐dimensional hydrodynamic and sediment transport modeling to test the sediment focusing hypothesis in upland lakes

Morales-Marín

French

Burningham

et al. 2017

Limnology & Oceanography

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“…Floderus (1989b) made fourteen synoptic sampling surveys in 1983-85, from which mud samples were recovered for analysis . Figure 2 shows the areal distribution of sediment types, based on visual identification of materials from the synoptic sampling surveys .…”

Section: Previous Studiesmentioning

confidence: 99%

“…Outside the bay, at 30 m depth, areas of accumulation prevail . The horizontal configuration of ephemeral mud blanket accumulations (defined as deposits with a discordant underlying surface and a water content exceeding 75%) has no regular distribution and small-scale variability and patchiness is high (Floderus, 1989b) . The mud blankets are probably derived from authochtonous sources since large volumes of mud (mean thickness about 4 mm) are deposited following algal blooms, during the spring and fall .…”

Section: Previous Studiesmentioning

confidence: 99%

“…Given the relatively stable chemical and physical properties of the mud blankets, it is possible to translate the thickness estimates (Floderus, 1989b) into amounts of nitrogen by using a conversion factor of 1 .2 mg N/cm -3 (assuming mean water content = 80% wet weight, bulk density = 1 .16 g/cm -3 and nitrogen content = 0 .52% dry weight) . Figure 5 presents a temporal distribution .…”

Section: Ephemeral Mud Blanketsmentioning

confidence: 99%

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Resuspension, ephemeral mud blankets and nitrogen cycling in Laholmsbukten, south east Kattegat

Floderus

H�kanson

1989

Hydrobiologia

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Primary production in coastal waters is generally nitrogen-limited due to efficient nitrogen sink pathways, which therefore limit further eutrophication . In this context, the significance of ephemeral mud blankets at shallow depth has been characterised using a simple computational box model . Bed materials from several synoptic grab-sample surveys in Laholmsbukten, a shallow embayment of the Kattegat Sea, were analysed . Sediment trap and current meter data provided an assessment of fine material transport ; the frequency of loose mud resuspension was estimated to vary between three and ten events per month in the spring, depending on the wind conditions .Mud blankets appear to be deposited following major spring and fall phytoplankton blooms, they are only a few centimetres thick, they are composed mainly of pelletized organic material and detritus and they have a high water content (80% wet weight) and nitrogen content (0 .5 % dry weight) . In the course of export from the bay, the muds undergo continuous resuspension, redeposition and biological breakdown . In one September day, the amount of particulate nitrogen redeposited in sediment traps was of equivalent magnitude to the entire mud blanket deposit (5 g N/m -2 or a 4 mm deposit as a bay-wide mean) . The presence of mud blankets is believe to control the nitrogen budget and water quality in the bay . A simple model proved compatible with observed mud blanket presence and rates of denitrification . Calm conditions are conducive to the loss of bound nitrogen and free oxygen within the bay as a result of prolonged denitrification and pelagic and benthic nitrogen regeneration . If fine particulates are rapidly exported from shallow bottoms, as in windy periods, the water quality of the entire Kattegat Sea is likely to be impaired .

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Data variability and uncertainty limits the capacity to identify and predict critical changes in coastal systems – A review of key concepts

Håkanson

Duarte

2008

Ocean & Coastal Management

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Sediment sampling evaluated with a new weighting function and index of reliability

Cited by 3 publications

References 6 publications

Three‐dimensional hydrodynamic and sediment transport modeling to test the sediment focusing hypothesis in upland lakes

Three‐dimensional hydrodynamic and sediment transport modeling to test the sediment focusing hypothesis in upland lakes

Resuspension, ephemeral mud blankets and nitrogen cycling in Laholmsbukten, south east Kattegat

Data variability and uncertainty limits the capacity to identify and predict critical changes in coastal systems – A review of key concepts

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