Multidecadal Evolution of the Turbidity Maximum Zone in a Macrotidal River Under Climate and Anthropogenic Pressures

Jalón‐Rojas, Isabel; Dijkstra, Yoeri M.; Schuttelaars, Henk M.; Brouwer, R.; Schmidt, Sabine; Sottolichio, Aldo

doi:10.1029/2020jc016273

Cited by 10 publications

(11 citation statements)

References 55 publications

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“…Wang et al, 2011). Studies on sediment in macrotidal estuaries mainly focused on sediment-induced stratification, turbidity maximum, sediment resuspension, flocculation and settling (e.g., Grasso et al, 2018;Jalón-Rojas et al, 2021;Tu et al, 2019;Y. P. Wang et al, 2013;Q.…”

Section: Discussionmentioning

confidence: 99%

“…Tidal pumping dominates suspended particle matter transport in well-mixed estuarine systems (Becherer et al, 2016). However, much attention has been paid on hydro-sediment dynamics in the macro-tidal estuaries (e.g., Jalón-Rojas et al, 2021;Ross et al, 2019;Tu et al, 2019), as well as the effects of tidal flat on hydro-sediment dynamics (e.g., Gao et al, 2018;Nidzieko & Ralston, 2012;Schaefer et al, 2022b). Large-scale morphodynamic behavior, such as that found in HZB, has been insufficiently examined.…”

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confidence: 99%

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Positive Feedback Between the Tidal Flat Variations and Sediment Dynamics: An Example Study in the Macro‐Tidal Turbid Hangzhou Bay

Ren

et al. 2023

JGR Oceans

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Tidal flat variations (curvature) in macro‐tidal turbid bays highly correlate with sediment dynamics. Interactions between tidal flats and sediment dynamics in macro‐tidal turbid estuaries, like Hangzhou Bay, China, have been studied through a fully validated 3D sediment model by considering high‐turbidity, flocculation, and water‐sediment density coupling. Numerical results show that the circulation and sediment flux in the curvature of Andong tidal flat have similar magnitudes in the along‐estuarine and lateral directions, demonstrating the important impact of the geometry on hydrodynamics and sediment transport processes. Sediment moves toward the southern/northern bank near the bottom/surface level in curvature. Tidally averaged net sediment flux is southward in the curvature. Tidal flat reclamation changes the curvature of the tidal channel, and modulates the circulation and sediment transport, and then feeds back to the tidal flat evolution subsequently. Bottom friction, nonlinear advection, and centrifugal force are dominant forces for inducing the lateral circulation, followed by the Coriolis force and sediment‐induced baroclinic process. Lateral circulation combined with the suspended sediment concentration (SSC) profile controls the distribution of instantaneous and tidally averaged net sediment fluxes in the curvature. The sediment flux positively correlates with the curvature of channel bends. The increased curvature of channel bends enhances the southward sediment fluxes mainly by increasing the effects of the centrifugal force, nonlinear advection, and Coriolis force on the lateral circulation and SSC. This study revealed a two‐way feedback system between tidal flat and sediment dynamics, which contributes to the impact of anthropogenic activities on geomorphological evolution of similar estuaries worldwide.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Positive Feedback Between the Tidal Flat Variations and Sediment Dynamics: An Example Study in the Macro‐Tidal Turbid Hangzhou Bay

Ren

et al. 2023

JGR Oceans

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“…From the 1950s until the 2010s, the point bar displays relative stability, with a near-constant volume and no major migration ( Gascuel, 2017 ). Over the same period, river discharges have been relatively low compared to the first half of the 20th century ( Billy et al, 2012 ), leading to the turbidity maximum zone (TMZ) migrating several kilometers upstream in the Garonne channel ( Jalón-Rojas et al, 2021 ). Decreasing river discharges could have led to an increase in fine sediment trapping (e.g., Virolle et al, 2019a ) and to the deposition of the tide-dominated sediments described in sequence 4 ( Figure 2 ).…”

Section: Discussionmentioning

confidence: 99%

Preservation of exopolymeric substances in estuarine sediments

et al. 2022

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The surface of intertidal estuarine sediments is covered with diatom biofilms excreting exopolymeric substances (EPSs) through photosynthesis. These EPSs are highly reactive and increase sediment cohesiveness notably through organo-mineral interactions. In most sedimentary environments, EPSs are partly to fully degraded by heterotrophic bacteria in the uppermost millimeters of the sediment and so they are thought to be virtually absent deeper in the sedimentary column. Here, we present the first evidence of the preservation of EPSs and EPS-mineral aggregates in a 6-m-long sedimentary core obtained from an estuarine point bar in the Gironde Estuary. EPSs were extracted from 18 depth intervals along the core, and their physicochemical properties were characterized by (i) wet chemical assays to measure the concentrations of polysaccharides and proteins, and EPS deprotonation of functional groups, (ii) acid–base titrations, and (iii) Fourier transform infrared spectroscopy. EPS-sediment complexes were also imaged using cryo-scanning electron microscopy. EPS results were analyzed in the context of sediment properties including facies, grain size, and total organic carbon, and of metabolic and enzymatic activities. Our results showed a predictable decrease in EPS concentrations (proteins and polysaccharides) and reactivity from the surface biofilm to a depth of 0.5 m, possibly linked to heterotrophic degradation. Concentrations remained relatively low down to ca. 4.3 m deep. Surprisingly, at that depth EPSs abundance was comparable to the surface and showed a downward decrease to 6.08 m. cryo-scanning electron microscopy (Cryo-SEM) showed that the EPS complexes with sediment were abundant at all studied depth and potentially protected EPSs from degradation. EPS composition did not change substantially from the surface to the bottom of the core. EPS concentrations and acidity were anti-correlated with metabolic activity, but showed no statistical correlation with grain size, TOC, depth or enzymatic activity. Maximum EPS concentrations were found at the top of tide-dominated sedimentary sequences, and very low concentrations were found in river flood-dominated sedimentary sequences. Based on this observation, we propose a scenario where biofilm development and EPS production are maximal when (i) the point bar and the intertidal areas were the most extensive, i.e., tide-dominated sequences and (ii) the tide-dominated deposit were succeeded by rapid burial beneath sediments, potentially decreasing the probability of encounter between bacterial cells and EPSs.

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“…Seasonal changes in humpback dolphin distributions are associated with seasonal changes in riverine discharges (Jefferson, 2000; Chen et al, 2010; Lin, Akamatsu & Chou, 2015), which could result from the river–tide interaction in the ETM area (Asp et al, 2018; Abascal‐Zorrilla et al, 2020). Reduction of river runoff (Karczmarski et al, 2017; Huang, Wang & Yao, 2018) and CEME construction can alter ETM dynamics (Yang et al, 2020; Jalón‐Rojas et al, 2021) and therefore cause a change in the distribution and habitat configuration of humpback dolphins (Karczmarski et al, 2017; Huang, Wang & Yao, 2018).…”

Section: Habitat Configuration Of the Indo‐pacific Humpback Dolphinmentioning

confidence: 99%

Habitat protection planning for Indo‐Pacific humpback dolphins (Sousa chinensis) in deteriorating environments: Knowledge gaps and recommendations for action

Huang

Peng

et al. 2021

Aquatic Conservation

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1. In Chinese and South-east Asian waters, the coastal and estuarine environments are important habitats for the Indo-Pacific humpback dolphin (Sousa chinensis).Coastal and estuarine maritime engineering (CEME), including land reclamation, embankment or shoreline armouring, harbour construction and marine farming, permanently changes coastal environments and threatens the long-term persistence of marine biota and ecosystems. Such impacts on humpback dolphin viability, however, are rarely discussed.

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Multidecadal Evolution of the Turbidity Maximum Zone in a Macrotidal River Under Climate and Anthropogenic Pressures

Cited by 10 publications

References 55 publications

Positive Feedback Between the Tidal Flat Variations and Sediment Dynamics: An Example Study in the Macro‐Tidal Turbid Hangzhou Bay

Positive Feedback Between the Tidal Flat Variations and Sediment Dynamics: An Example Study in the Macro‐Tidal Turbid Hangzhou Bay

Preservation of exopolymeric substances in estuarine sediments

Habitat protection planning for Indo‐Pacific humpback dolphins (Sousa chinensis) in deteriorating environments: Knowledge gaps and recommendations for action

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