Chapter 7 Sediment Transport Processes in Coastal Lagoons

Nichols, Maynard M.; Boon, John D.

doi:10.1016/s0422-9894(08)70012-6

Cited by 64 publications

(53 citation statements)

References 44 publications

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“…salt marsh plants, macroalgae, seagrass and their epiphytes). This δ 13 C pattern was observed in the neighbouring Lapalme Lagoon across all seasons (Carlier et al 2007a) and is consistent with the well-recognized idea that the SOM pool of estuarine and lagoon ecosystems generally consists of a complex mixture of several sources of organic matter (Nichols & Allen 1981, Deegan & Garritt 1997. The range in δ 13 C values found for SOM (-21.6 to -16.6 ‰) indicates that the different sources contributed in varying proportions to the SOM pool, depending on the location in the lagoon.…”

Section: Overall Food Web Structuresupporting

confidence: 83%

Spatial heterogeneity in the food web of a heavily modified Mediterranean coastal lagoon: stable isotope evidence

Carlier¹,

Riera²,

Amouroux³

et al. 2009

Aquat. Biol.

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International audienceWe investigated the food web structure of the Salses-Leucate Lagoon (northwestern Mediterranean) through delta C-13 and delta N-15 analysis of its benthic macrofauna and potential food sources. This lagoon was heavily human-modified during the 1970s, allowing permanent exchange with the open sea and an increase in salinity from that time. As a result, it exhibits a much less marked salinity gradient than the neighbouring lagoon ecosystems, which Suggests a priori that its food web structure is more homogeneous. In this environmental context, we assessed spatial variability in the isotopic composition of non-vagrant macrofauna in Salses-Leucate in relation to degree of connection with the open sea, anthropogenic inputs and the presence of oyster aquaculture. Overall, the main trophic pathway is based on suspended particulate organic matter and sedimented organic matter. However, there were marked spatial differences (at different scales) in both delta C-13 and delta N-15 values of macrofauna, which suggests an important feeding plasticity within each category of primary consumers at a small spatial scale. delta C-13 data showed that the contributions of the different food sources to the diet of primary consumers changed depending on distance from continental inputs, connection with the open sea and local primary producer coverage. Small-scale delta N-15 variability revealed a very localised influence of anthropogenic nitrogen output. Regarding the possible effect of aquaculture, the isotopic ratios of sediment and macrobenthos were not modified underneath the oyster lines with respect to the neighbouring area. Conversely, the isotopic signature of consumers living on the oyster lines contrasted with those living underneath. Therefore, our results suggest that a decoupling exists between the trophic pathways that occur in the water column and on the soft bottom of this shallow water ecosystem

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Section: Overall Food Web Structuresupporting

confidence: 83%

Spatial heterogeneity in the food web of a heavily modified Mediterranean coastal lagoon: stable isotope evidence

Carlier¹,

Riera²,

Amouroux³

et al. 2009

Aquat. Biol.

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“…(22), drastically reducing the sediment supply to the near-shore continental shelf. The lack of offshore sediment inputs is one of the causes of sediment starvation within the Virginia marshes (12,23). An exception is notable in the southern portion of the Virginia Coast Reserve, where close proximity to a sediment depositional cell formed by tidal fluxes out of Chesapeake Bay promotes higher sediment availability (24).…”

Section: Discussionmentioning

confidence: 99%

Critical width of tidal flats triggers marsh collapse in the absence of sea-level rise

Mariotti

Fagherazzi

2013

Proc. Natl. Acad. Sci. U.S.A.

250

263

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High rates of wave-induced erosion along salt marsh boundaries challenge the idea that marsh survival is dictated by the competition between vertical sediment accretion and relative sea-level rise. Because waves pounding marshes are often locally generated in enclosed basins, the depth and width of surrounding tidal flats have a pivoting control on marsh erosion. Here, we show the existence of a threshold width for tidal flats bordering salt marshes. Once this threshold is exceeded, irreversible marsh erosion takes place even in the absence of sea-level rise. This catastrophic collapse occurs because of the positive feedbacks among tidal flat widening by wave-induced marsh erosion, tidal flat deepening driven by wave bed shear stress, and local wind wave generation. The threshold width is determined by analyzing the 50-y evolution of 54 marsh basins along the US Atlantic Coast. The presence of a critical basin width is predicted by a dynamic model that accounts for both horizontal marsh migration and vertical adjustment of marshes and tidal flats. Variability in sediment supply, rather than in relative sea-level rise or wind regime, explains the different critical width, and hence erosion vulnerability, found at different sites. We conclude that sediment starvation of coastlines produced by river dredging and damming is a major anthropogenic driver of marsh loss at the study sites and generates effects at least comparable to the accelerating sea-level rise due to global warming.salt marsh boundary erosion | wave erosion W ave-induced boundary erosion is a leading process threatening salt marshes (1, 2), but it is remarkably unexplored compared with the vertical dynamics of the marsh platform (3, 4). Wave-induced boundary erosion is particularly relevant along coastlines with limited subsidence such as the Mid-Atlantic coast of the United States, where large marsh areas are deteriorating (5, 6) despite marsh accretion keeping pace with contemporary rates of sea-level rise (7,8). Here, we focus on the evolution of three salt marsh sites on the US Atlantic Coast, subjected to different rates of wave-induced boundary erosion: Cape May, NJ, Virginia Coast Reserve, VA, and Charleston Sound, SC (Fig. 1). All sites are characterized by barrier islands sheltering shallow bays with extensive salt marshes and tidal flats. The bays are connected to the open sea by multiple inlets, experience limited direct riverine inputs (9, 10), and are subject to similar wind conditions (SI Text). Relative sea-level rise (RSLR) is on the order of 2 mm/y and tidal range of ∼1.4 m (SI Text). These embayments are characterized by rounded tidal flats surrounded by salt marshes, which are referred to as marsh basins (11,12).Stevenson et al. (13) reported loss of brackish marshes driven by the enlargement of marsh basins, referred to by the authors as ponds. They suggested the existence of a pond threshold width that, once exceeded, leads to ponds widening by wave-induced boundary erosion. Here, we expand this idea by (i) developing a physical...

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“…The behavior, observed by Nichols and Boon [1994] in Arcachon Bay (Figure 2-B) and by Van Straaten and Kuenen [1957] in the Lauwerszee (Figure 1), is reproduced and, compared to the reference scenario, enhanced (Figure 4-C). This observation supports the hypothesis on tidal dominated basins (as the relative tidal dominance increased compared to the reference scenario).…”

Section: Large Tidal Range Scenariomentioning

confidence: 56%

“…Furthermore, Nichols and Boon [1994] introduced a classification of various systems. Two of these are given in Figure As a hypothesis, which is relating this classification to physics, a (relatively) wave-or tide-dominated system can be proposed for case A and B, respectively.…”

Section: Introductionmentioning

confidence: 99%

Simulating the large-scale spatial sand-mud distribution in a schematized process-based tidal inlet system model

Scheel¹,

Ledden²,

Prooijen³

et al. 2012

NCK-days 2012: Crossing Borders in Coastal Research: Jubilee Conference Proceedings

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Tidal basins, as found in the Dutch Wadden Sea, are characterized by strong spatial variations in bathymetry and sediment distribution. In this contribution, the aim is at simulating the spatial sand-mud distribution of a tidal basin. Predicting this spatial distribution is however complicated, due to the non-linear interactions between tides, waves, sediment transport, morphology and biology. To reduce complexity, while increasing physical understanding, an idealized schematization of the Amelander inlet system is considered. Delft3D is applied with a recently developed bed module, containing various sediment layers, combined with formulations for both cohesive and non-cohesive sediment mixtures. Starting with uniform mud content in the spatial domain, the development of the sediment distribution is simulated. Realistic sand-mud patterns are found, with accumulation of mud on the tidal flats. The schematization is further used to determine the sensitivity of the sand-mud patterns to changes in tide, while assessing the influence of tidal dominance on the large-scale sand-mud patterns. The patterns are enhanced/diminished under the influence of higher/lower tides.

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Chapter 7 Sediment Transport Processes in Coastal Lagoons

Cited by 64 publications

References 44 publications

Spatial heterogeneity in the food web of a heavily modified Mediterranean coastal lagoon: stable isotope evidence

Spatial heterogeneity in the food web of a heavily modified Mediterranean coastal lagoon: stable isotope evidence

Critical width of tidal flats triggers marsh collapse in the absence of sea-level rise

Simulating the large-scale spatial sand-mud distribution in a schematized process-based tidal inlet system model

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