Eco-Morphological Problems in the Yangtze Estuary and the Western Scheldt

Vriend, H.J. de; Wang, Zheng Bing; Ysebaert, Tom; Herman, Peter M. J.; Ding, Pingxing

doi:10.1007/s13157-011-0239-7

Cited by 66 publications

(66 citation statements)

References 32 publications

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“…The estuary experiences a semidiurnal tide, with a mean tidal range of 3.8m at the mouth, and 5m at the Dutch-Belgian border (Eleveld et al, 2014). The estuary is turbid, well-mixed and river discharge is low, ca 100 m 3 s -1 (De Vriend et al, 2011;Eleveld et al, 2014).…”

Section: Study Areamentioning

confidence: 99%

Hydrodynamic conditioning of diversity and functional traits in subtidal estuarine macrozoobenthic communities

Wal

Lambert

Ysebaert

et al. 2017

Estuarine, Coastal and Shelf Science

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2 Highlights: Richness of subtidal estuarine macrofauna depended on currents and sediment properties  Community composition and functional traits shifted with currents and sediment properties  Salinity, water depth and distance from tidal flats had a minor effect  Hydrodynamic models can predict hotspots and coldspots in ecological richness 3 ABSTRACTVariations in abundance and diversity of estuarine benthic macrofauna are typically described along the salinity gradient. The influence of gradients in water depth, hydrodynamic energy and sediment properties are less well known. We studied how these variables influence the distribution of subtidal macrofauna in the polyhaline zone of a temperate estuary (Westerschelde). Macrofauna density, biomass and species richness, combined in a so-called ecological richness, decreased with current velocities and median grain-size and increased with organic carbon of the sediment, in total explaining 39% of the variation. The macrofauna community composition was less well explained by the three environmental variables (ca 12-15% in total, with current velocity explaining ca 8%). Salinity, water depth and distance to the intertidal zone had a very limited effect on both ecological richness and the macrofauna community.The proportion of (surface) deposit feeders (including opportunistic species), decreased relative to that of omnivores and carnivores with increasing current velocity and sediment grain-size. In parallel, the proportion of burrowing sessile benthic species decreased relative to that of mobile benthic species that are able to swim. Correspondingly, spatial variations in hydrodynamics yielded distinct hotspots and coldspots in ecological richness. The findings highlight the importance of local hydrodynamic conditions for estuarine restoration and conservation. The study provides a tool based on a hydrodynamic model to assess and predict ecological richness in estuaries.

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Section: Study Areamentioning

confidence: 99%

Hydrodynamic conditioning of diversity and functional traits in subtidal estuarine macrozoobenthic communities

Wal

Lambert

Ysebaert

et al. 2017

Estuarine, Coastal and Shelf Science

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“…The Scheldt estuary experiences a number of human-induced processes that can increase sediment deposition on tidal flats, among which dredging and the local deposition of dredged sediments at the edges of tidal flats are some of the most important examples (De Vriend et al, 2011;van der Wal et al, 2011). The Paulina mudflat harbours a functionally rich benthic macrofaunal community that is numerically dominated by polychaetes (Van Colen et al, 2008.…”

Section: Sample Collection and Experimental Set-upmentioning

confidence: 99%

“…Our study was performed on a mudflat in the estuary of the river Scheldt (Belgium, the Netherlands), which is characterized by its meso-to macrotidal regime and well-mixed water column. Sediment input from the river basin is relatively low and sand extraction and sea level rise lead to a net export of sediment from the estuary (De Vriend et al, 2011). Sediment accretion on the estuary's tidal flats can amount to about 2 cm yr −1 (Weerman et al, 2011;Widdows et al, 2004), which suggests that natural sedimentation on the intertidal mudflats is unlikely to exceed even a few millimetres per tidal cycle.…”

Section: Introductionmentioning

confidence: 99%

“…Besides natural processes, anthropogenic factors influencing sedimentation are prominent in the estuary, among which dredging in the main channels to ensure access to the port of Antwerp and dumping of the dredged material to retain sediment within the estuary are the most important (Jeuken and Wang, 2010;Meire et al, 2005). Most of this dredged sediment is disposed of near shoals and tidal flats and can thus affect the intertidal ecosystem (Bolam and Whomersley, 2005;De Vriend et al, 2011;Zheng, 2015). The effects of sediment deposition on taxonomic diversity (Thrush et al, 2003), behaviour (Hohaia et al, 2014;Townsend et al, 2014), and ecosystem functioning (Larson and Sundbäck, 2012;Montserrat et al, 2011) have recently received considerable attention.…”

Section: Introductionmentioning

confidence: 99%

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Functional trait responses to sediment deposition reduce macrofauna-mediated ecosystem functioning in an estuarine mudflat

et al. 2018

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Abstract. Human activities, among which dredging and land use change in river basins, are altering estuarine ecosystems. These activities may result in changes in sedimentary processes, affecting biodiversity of sediment macrofauna. As macrofauna controls sediment chemistry and fluxes of energy and matter between water column and sediment, changes in the structure of macrobenthic communities could affect the functioning of an entire ecosystem. We assessed the impact of sediment deposition on intertidal macrobenthic communities and on rates of an important ecosystem function, i.e. sediment community oxygen consumption (SCOC). An experiment was performed with undisturbed sediment samples from the Scheldt river estuary (SW Netherlands). The samples were subjected to four sedimentation regimes: one control and three with a deposited sediment layer of 1, 2 or 5 cm. Oxygen consumption was measured during incubation at ambient temperature. Luminophores applied at the surface, and a seawater-bromide mixture, served as tracers for bioturbation and bio-irrigation, respectively. After incubation, the macrofauna was extracted, identified, and counted and then classified into functional groups based on motility and sediment reworking capacity. Total macrofaunal densities dropped already under the thinnest deposits. The most affected fauna were surficial and low-motility animals, occurring at high densities in the control. Their mortality resulted in a drop in SCOC, which decreased steadily with increasing deposit thickness, while bio-irrigation and bioturbation activity showed increases in the lower sediment deposition regimes but decreases in the more extreme treatments. The initial increased activity likely counteracted the effects of the drop in low-motility, surficial fauna densities, resulting in a steady rather than sudden fall in oxygen consumption. We conclude that the functional identity in terms of motility and sediment reworking can be crucial in our understanding of the regulation of ecosystem functioning and the impact of habitat alterations such as sediment deposition.

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“…Bouma et al, 2005). For example in the Western Scheldt, the shipping fairway is now maintained at a depth of 14.5m below Lowest Astronomical Tide (de Vriend et al, 2011;Depreiter et al, 2012 In contrast, low-dynamic intertidal areas are valuable ecological habitat, for example for the Western Scheldt there is an obligation to maintain a certain amount of intertidal area (Depreiter et al, 2012). Previously, Townend (2008) showed that 15 basin hypsometry can be a tool to design breaches in managed re-alignment sites and can provide an indication of habitat composition.…”

Section: Implications For Management Of Estuariesmentioning

confidence: 99%

Morphology of bar-built estuaries: relation between planform shape and depth distribution

Leuven

Selaković

Kleinhans

2018

Preprint

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Abstract. Fluvial-tidal transitions in estuaries are used as major shipping fairways and are characterised by complex bar and channel patterns with a large biodiversity. Habitat suitability assessment and study of interactions between morphology and ecology therefore require bathymetric data. While imagery offers data of planform estuary dimensions, only for a few natural estuaries bathymetries are available. Here we study the relation between along-channel planform geometry, obtained as the outline from imagery, and hypsometry, which characterises the distribution of along-channel and cross-channel bed-levels. 5We fitted the original function of Strahler (1952) to bathymetric data along four natural estuaries. Comparison to planform estuary shape shows that hypsometry is concave at narrow sections with large channels, while complex bar morphology results in more convex hypsometry. We found a relation between hypsometric function shape and the degree to which the estuary width deviates from an ideal convergent estuary, which is calculated from river width and mouth width. This implies that the occurring bed level distributions depend on inherited Holocene topography and lithology. Our new empirical function 10 predicts hypsometry and along-channel variation in intertidal and subtidal width. Combination with the tidal amplitude allows an estimate of inundation duration. A validation of the results on available bathymetry shows that predictions of intertidal and subtidal area are accurate within a factor 2 for estuaries of different size and character. Locations with major human influence deviate from the general trends, because dredging, dumping, land reclamation and other engineering measures cause local deviations from the expected bed-level distributions. The bathymetry predictor can be used to characterise and predict 15 estuarine subtidal and intertidal morphology in data-poor environments.

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Eco-Morphological Problems in the Yangtze Estuary and the Western Scheldt

Cited by 66 publications

References 32 publications

Hydrodynamic conditioning of diversity and functional traits in subtidal estuarine macrozoobenthic communities

Hydrodynamic conditioning of diversity and functional traits in subtidal estuarine macrozoobenthic communities

Functional trait responses to sediment deposition reduce macrofauna-mediated ecosystem functioning in an estuarine mudflat

Morphology of bar-built estuaries: relation between planform shape and depth distribution

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