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Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site

Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site
Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site
Managed realignment (MR) schemes are being implemented to compensate for the loss of intertidal saltmarsh habitats by breaching flood defences and inundating the formerly defended coastal hinterland. However, studies have shown that MR sites have lower biodiversity than anticipated, which has been linked with anoxia and poor drainage resulting from compaction and the collapse of sediment pore space caused by the site's former terrestrial land use. Despite this proposed link between biodiversity and soil structure, the evolution of the sediment sub-surface following site inundation has rarely been examined, particularly over the early stages of the terrestrial to marine or estuarine transition. This paper presents a novel combination of broad- and intensive-scale analysis of the sub-surface evolution of the Medmerry Managed Realignment Site (West Sussex, UK) in the three years following site inundation. Repeated broad-scale sediment physiochemical datasets are analysed to assess the early changes in the sediment subsurface and the preservation of the former terrestrial surface, comparing four locations of different former land uses. Additionally, for two of these locations, high-intensity 3D-computed X-ray microtomography and Itrax micro-X-ray fluorescence spectrometry analyses are presented. Results provide new data on differences in sediment properties and structure related to the former land use, indicating that increased agricultural activity leads to increased compaction and reduced porosity. The presence of anoxic conditions, indicative of poor hydrological connectivity between the terrestrial and post-inundation intertidal sediment facies, was only detected at one site. This site has experienced the highest rate of accretion over the terrestrial surface (ca. 7 cm over 36 months), suggesting that poor drainage is caused by the interaction (or lack of) between sediment facies rather than the former land use. This has significant implications for the design of future MR sites in terms of preparing sites, their anticipated evolution, and the delivery of ecosystem services.
0048-9697
1419-1432
Dale, Jonathan
f998e92c-cd34-45c2-bc2c-d38ff72b6edc
Cundy, Andrew B.
994fdc96-2dce-40f4-b74b-dc638286eb08
Spencer, Kate L.
f9bb5735-8798-448d-a0ba-a7238d9aac3e
Carr, Simon J.
f3f07ba4-511f-4898-93d0-d53b8e560328
Croudace, Ian W.
24deb068-d096-485e-8a23-a32b7a68afaf
Burgess, Heidi M.
96772c7e-ab57-463f-8979-b70dd5a360c3
Nash, David J.
a364e478-e641-48a9-ad56-93984f811c16
Dale, Jonathan
f998e92c-cd34-45c2-bc2c-d38ff72b6edc
Cundy, Andrew B.
994fdc96-2dce-40f4-b74b-dc638286eb08
Spencer, Kate L.
f9bb5735-8798-448d-a0ba-a7238d9aac3e
Carr, Simon J.
f3f07ba4-511f-4898-93d0-d53b8e560328
Croudace, Ian W.
24deb068-d096-485e-8a23-a32b7a68afaf
Burgess, Heidi M.
96772c7e-ab57-463f-8979-b70dd5a360c3
Nash, David J.
a364e478-e641-48a9-ad56-93984f811c16

Dale, Jonathan, Cundy, Andrew B., Spencer, Kate L., Carr, Simon J., Croudace, Ian W., Burgess, Heidi M. and Nash, David J. (2019) Sediment structure and physicochemical changes following tidal inundation at a large open coast managed realignment site. Science of the Total Environment, 660, 1419-1432. (doi:10.1016/j.scitotenv.2018.12.323).

Record type: Article

Abstract

Managed realignment (MR) schemes are being implemented to compensate for the loss of intertidal saltmarsh habitats by breaching flood defences and inundating the formerly defended coastal hinterland. However, studies have shown that MR sites have lower biodiversity than anticipated, which has been linked with anoxia and poor drainage resulting from compaction and the collapse of sediment pore space caused by the site's former terrestrial land use. Despite this proposed link between biodiversity and soil structure, the evolution of the sediment sub-surface following site inundation has rarely been examined, particularly over the early stages of the terrestrial to marine or estuarine transition. This paper presents a novel combination of broad- and intensive-scale analysis of the sub-surface evolution of the Medmerry Managed Realignment Site (West Sussex, UK) in the three years following site inundation. Repeated broad-scale sediment physiochemical datasets are analysed to assess the early changes in the sediment subsurface and the preservation of the former terrestrial surface, comparing four locations of different former land uses. Additionally, for two of these locations, high-intensity 3D-computed X-ray microtomography and Itrax micro-X-ray fluorescence spectrometry analyses are presented. Results provide new data on differences in sediment properties and structure related to the former land use, indicating that increased agricultural activity leads to increased compaction and reduced porosity. The presence of anoxic conditions, indicative of poor hydrological connectivity between the terrestrial and post-inundation intertidal sediment facies, was only detected at one site. This site has experienced the highest rate of accretion over the terrestrial surface (ca. 7 cm over 36 months), suggesting that poor drainage is caused by the interaction (or lack of) between sediment facies rather than the former land use. This has significant implications for the design of future MR sites in terms of preparing sites, their anticipated evolution, and the delivery of ecosystem services.

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Medmerry Cores Paper - Accepted Manuscript
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More information

Accepted/In Press date: 21 December 2018
e-pub ahead of print date: 28 December 2018
Published date: 10 April 2019

Identifiers

Local EPrints ID: 427812
URI: https://eprints.soton.ac.uk/id/eprint/427812
ISSN: 0048-9697
PURE UUID: 1e3fd449-94e5-462d-a07d-75119ebb33c7
ORCID for Andrew B. Cundy: ORCID iD orcid.org/0000-0003-4368-2569

Catalogue record

Date deposited: 29 Jan 2019 17:30
Last modified: 20 Jul 2019 00:34

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